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Example of how human behaviour studies cannot be applied to all people.

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In the Summer of 1995, a young graduate student in anthropology at UCLA named Joe Henrich traveled to Peru to carry out some fieldwork among the Machiguenga, an indigenous people who live north of Machu Picchu in the Amazon basin. The Machiguenga had traditionally been horticulturalists who lived in single-family, thatch-roofed houses in small hamlets composed of clusters of extended families. For sustenance, they relied on local game and produce from small-scale farming. They shared with their kin but rarely traded with outside groups.

While the setting was fairly typical for an anthropologist, Henrich's research was not. Rather than practice traditional ethnography, he decided to run a behavioral experiment that had been developed by economists. Henrich used a "game"-along the lines of the famous prisoner's dilemma -to see whether isolated cultures shared with the West the same basic instinct for fairness. In doing so, Henrich expected to confirm one of the foundational assumptions underlying such experiments, and indeed underpinning the entire fields of economics and psychology: that humans all share the same cognitive machinery-the same evolved rational and psychological hardwiring.

The test that Henrich introduced to the Machiguenga was called the ultimatum game. The rules are simple: in each game there are two players who remain anonymous to each other. The first player is given an amount of money, say $100, and told that he has to offer some of the cash, in an amount of his choosing, to the other subject. The second player can accept or refuse the split. But there's a hitch: players know that if the recipient refuses the offer, both leave empty-handed. North Americans, who are the most common subjects for such experiments, usually offer a 50-50 split when on the giving end. When on the receiving end, they show an eagerness to punish the other player for uneven splits at their own expense. In short, Americans show the tendency to be equitable with strangers-and to punish those who are not.

Among the Machiguenga, word quickly spread of the young, square-jawed visitor from America giving away money. The stakes Henrich used in the game with the Machiguenga were not insubstantial-roughly equivalent to the few days' wages they sometimes earned from episodic work with logging or oil companies. So Henrich had no problem finding volunteers. What he had great difficulty with, however, was explaining the rules, as the game struck the Machiguenga as deeply odd.

When he began to run the game it became immediately clear that Machiguengan behavior was dramatically different from that of the average North American. To begin with, the offers from the first player were much lower. In addition, when on the receiving end of the game, the Machiguenga rarely refused even the lowest possible amount. "It just seemed ridiculous to the Machiguenga that you would reject an offer of free money," says Henrich. "They just didn't understand why anyone would sacrifice money to punish someone who had the good luck of getting to play the other role in the game."

The potential implications of the unexpected results were quickly apparent to Henrich. He knew that a vast amount of scholarly literature in the social sciences-particularly in economics and psychology-relied on the ultimatum game and similar experiments. At the heart of most of that research was the implicit assumption that the results revealed evolved psychological traits common to all humans, never mind that the test subjects were nearly always from the industrialized West. Henrich realized that if the Machiguenga results stood up, and if similar differences could be measured across other populations, this assumption of universality would have to be challenged.

Henrich had thought he would be adding a small branch to an established tree of knowledge. It turned out he was sawing at the very trunk. He began to wonder: What other certainties about "human nature" in social science research would need to be reconsidered when tested across diverse populations?

Henrich soon landed a grant from the MacArthur Foundation to take his fairness games on the road. With the help of a dozen other colleagues he led a study of 14 other small-scale societies, in locales from Tanzania to Indonesia. Differences abounded in the behavior of both players in the ultimatum game. In no society did he find people who were purely selfish (that is, who always offered the lowest amount, and never refused a split), but average offers from place to place varied widely and, in some societies-ones where gift-giving is heavily used to curry favor or gain allegiance-the first player would often make overly generous offers in excess of 60 percent, and the second player would often reject them, behaviors almost never observed among Americans.

The research established Henrich as an up-and-coming scholar. In 2004, he was given the U.S. Presidential Early Career Award for young scientists at the White House. But his work also made him a controversial figure. When he presented his research to the anthropology department at the University of British Columbia during a job interview a year later, he recalls a hostile reception. Anthropology is the social science most interested in cultural differences, but the young scholar's methods of using games and statistics to test and compare cultures with the West seemed heavy-handed and invasive to some. "Professors from the anthropology department suggested it was a bad thing that I was doing," Henrich remembers. "The word 'unethical' came up."

So instead of toeing the line, he switched teams. A few well-placed people at the University of British Columbia saw great promise in Henrich's work and created a position for him, split between the economics department and the psychology department. It was in the psychology department that he found two kindred spirits in Steven Heine and Ara Norenzayan. Together the three set about writing a paper that they hoped would fundamentally challenge the way social scientists thought about human behavior, cognition, and culture.

A modern liberal arts education gives lots of lip service to the idea of cultural diversity. It's generally agreed that all of us see the world in ways that are sometimes socially and culturally constructed, that pluralism is good, and that ethnocentrism is bad. But beyond that the ideas get muddy. That we should welcome and celebrate people of all backgrounds seems obvious, but the implied corollary-that people from different ethno-cultural origins have particular attributes that add spice to the body politic-becomes more problematic. To avoid stereotyping, it is rarely stated bluntly just exactly what those culturally derived qualities might be. Challenge liberal arts graduates on their appreciation of cultural diversity and you'll often find them retreating to the anodyne notion that under the skin everyone is really alike.

If you take a broad look at the social science curriculum of the last few decades, it becomes a little more clear why modern graduates are so unmoored. The last generation or two of undergraduates have largely been taught by a cohort of social scientists busily doing penance for the racism and Eurocentrism of their predecessors, albeit in different ways. Many anthropologists took to the navel gazing of postmodernism and swore off attempts at rationality and science, which were disparaged as weapons of cultural imperialism.

Economists and psychologists, for their part, did an end run around the issue with the convenient assumption that their job was to study the human mind stripped of culture. The human brain is genetically comparable around the globe, it was agreed, so human hardwiring for much behavior, perception, and cognition should be similarly universal. No need, in that case, to look beyond the convenient population of undergraduates for test subjects. A 2008 survey of the top six psychology journals dramatically shows how common that assumption was: more than 96 percent of the subjects tested in psychological studies from 2003 to 2007 were Westerners-with nearly 70 percent from the United States alone. Put another way: 96 percent of human subjects in these studies came from countries that represent only 12 percent of the world's population.

Henrich's work with the ultimatum game was an example of a small but growing countertrend in the social sciences, one in which researchers look straight at the question of how deeply culture shapes human cognition. His new colleagues in the psychology department, Heine and Norenzayan, were also part of this trend. Heine focused on the different ways people in Western and Eastern cultures perceived the world, reasoned, and understood themselves in relationship to others. Norenzayan's research focused on the ways religious belief influenced bonding and behavior. The three began to compile examples of cross-cultural research that, like Henrich's work with the Machiguenga, challenged long-held assumptions of human psychological universality.

Some of that research went back a generation. It was in the 1960s, for instance, that researchers discovered that aspects of visual perception were different from place to place. One of the classics of the literature, the Müller-Lyer illusion, showed that where you grew up would determine to what degree you would fall prey to the illusion that these two lines are different in length:

Researchers found that Americans perceive the line with the ends feathered outward (B) as being longer than the line with the arrow tips (A). San foragers of the Kalahari, on the other hand, were more likely to see the lines as they are: equal in length. Subjects from more than a dozen cultures were tested, and Americans were at the far end of the distribution-seeing the illusion more dramatically than all others.

More recently psychologists had challenged the universality of research done in the 1950s by pioneering social psychologist Solomon Asch. Asch had discovered that test subjects were often willing to make incorrect judgments on simple perception tests to conform with group pressure. When the test was performed across 17 societies, however, it turned out that group pressure had a range of influence. Americans were again at the far end of the scale, in this case showing the least tendency to conform to group belief.

As Heine, Norenzayan, and Henrich furthered their search, they began to find research suggesting wide cultural differences almost everywhere they looked: in spatial reasoning, the way we infer the motivations of others, categorization, moral reasoning, the boundaries between the self and others, and other arenas. These differences, they believed, were not genetic. The distinct ways Americans and Machiguengans played the ultimatum game, for instance, wasn't because they had differently evolved brains. Rather, Americans, without fully realizing it, were manifesting a psychological tendency shared with people in other industrialized countries that had been refined and handed down through thousands of generations in ever more complex market economies. When people are constantly doing business with strangers, it helps when they have the desire to go out of their way (with a lawsuit, a call to the Better Business Bureau, or a bad Yelp review) when they feel cheated. Because Machiguengan culture had a different history, their gut feeling about what was fair was distinctly their own. In the small-scale societies with a strong culture of gift-giving, yet another conception of fairness prevailed. There, generous financial offers were turned down because people's minds had been shaped by a cultural norm that taught them that the acceptance of generous gifts brought burdensome obligations. Our economies hadn't been shaped by our sense of fairness; it was the other way around.

The growing body of cross-cultural research that the three researchers were compiling suggested that the mind's capacity to mold itself to cultural and environmental settings was far greater than had been assumed. The most interesting thing about cultures may not be in the observable things they do-the rituals, eating preferences, codes of behavior, and the like-but in the way they mold our most fundamental conscious and unconscious thinking and perception.

For instance, the different ways people perceive the Müller-Lyer illusion likely reflects lifetimes spent in different physical environments. American children, for the most part, grow up in box-shaped rooms of varying dimensions. Surrounded by carpentered corners, visual perception adapts to this strange new environment (strange and new in terms of human history, that is) by learning to perceive converging lines in three dimensions.

When unconsciously translated in three dimensions, the line with the outward-feathered ends (C) appears farther away and the brain therefore judges it to be longer. The more time one spends in natural environments, where there are no carpentered corners, the less one sees the illusion.

As the three continued their work, they noticed something else that was remarkable: again and again one group of people appeared to be particularly unusual when compared to other populations-with perceptions, behaviors, and motivations that were almost always sliding down one end of the human bell curve.

In the end they titled their paper "The Weirdest People in the World?" (pdf) By "weird" they meant both unusual and Western, Educated, Industrialized, Rich, and Democratic. It is not just our Western habits and cultural preferences that are different from the rest of the world, it appears. The very way we think about ourselves and others-and even the way we perceive reality-makes us distinct from other humans on the planet, not to mention from the vast majority of our ancestors. Among Westerners, the data showed that Americans were often the most unusual, leading the researchers to conclude that "American participants are exceptional even within the unusual population of Westerners-outliers among outliers."

Given the data, they concluded that social scientists could not possibly have picked a worse population from which to draw broad generalizations. Researchers had been doing the equivalent of studying penguins while believing that they were learning insights applicable to all birds.

Not long ago I met Henrich, Heine, and Norenzayan for dinner at a small French restaurant in Vancouver, British Columbia, to hear about the reception of their weird paper, which was published in the prestigious journal Behavioral and Brain Sciences in 2010. The trio of researchers are young-as professors go-good-humored family men. They recalled that they were nervous as the publication time approached. The paper basically suggested that much of what social scientists thought they knew about fundamental aspects of human cognition was likely only true of one small slice of humanity. They were making such a broadside challenge to whole libraries of research that they steeled themselves to the possibility of becoming outcasts in their own fields.

"We were scared," admitted Henrich. "We were warned that a lot of people were going to be upset."

"We were told we were going to get spit on," interjected Norenzayan.

"Yes," Henrich said. "That we'd go to conferences and no one was going to sit next to us at lunchtime."

Interestingly, they seemed much less concerned that they had used the pejorative acronym WEIRD to describe a significant slice of humanity, although they did admit that they could only have done so to describe their own group. "Really," said Henrich, "the only people we could have called weird are represented right here at this table."

Still, I had to wonder whether describing the Western mind, and the American mind in particular, as weird suggested that our cognition is not just different but somehow malformed or twisted. In their paper the trio pointed out cross-cultural studies that suggest that the "weird" Western mind is the most self-aggrandizing and egotistical on the planet: we are more likely to promote ourselves as individuals versus advancing as a group. WEIRD minds are also more analytic, possessing the tendency to telescope in on an object of interest rather than understanding that object in the context of what is around it.

The WEIRD mind also appears to be unique in terms of how it comes to understand and interact with the natural world. Studies show that Western urban children grow up so closed off in man-made environments that their brains never form a deep or complex connection to the natural world. While studying children from the U.S., researchers have suggested a developmental timeline for what is called "folkbiological reasoning." These studies posit that it is not until children are around 7 years old that they stop projecting human qualities onto animals and begin to understand that humans are one animal among many. Compared to Yucatec Maya communities in Mexico, however, Western urban children appear to be developmentally delayed in this regard. Children who grow up constantly interacting with the natural world are much less likely to anthropomorphize other living things into late childhood.

Given that people living in WEIRD societies don't routinely encounter or interact with animals other than humans or pets, it's not surprising that they end up with a rather cartoonish understanding of the natural world. "Indeed," the report concluded, "studying the cognitive development of folkbiology in urban children would seem the equivalent of studying 'normal' physical growth in malnourished children."

During our dinner, I admitted to Heine, Henrich, and Norenzayan that the idea that I can only perceive reality through a distorted cultural lens was unnerving. For me the notion raised all sorts of metaphysical questions: Is my thinking so strange that I have little hope of understanding people from other cultures? Can I mold my own psyche or the psyches of my children to be less WEIRD and more able to think like the rest of the world? If I did, would I be happier?

Henrich reacted with mild concern that I was taking this research so personally. He had not intended, he told me, for his work to be read as postmodern self-help advice. "I think we're really interested in these questions for the questions' sake," he said.

The three insisted that their goal was not to say that one culturally shaped psychology was better or worse than another-only that we'll never truly understand human behavior and cognition until we expand the sample pool beyond its current small slice of humanity. Despite these assurances, however, I found it hard not to read a message between the lines of their research. When they write, for example, that weird children develop their understanding of the natural world in a "culturally and experientially impoverished environment" and that they are in this way the equivalent of "malnourished children," it's difficult to see this as a good thing.

The turn that Henrich, Heine, and Norenzayan are asking social scientists to make is not an easy one: accounting for the influence of culture on cognition will be a herculean task. Cultures are not monolithic; they can be endlessly parsed. Ethnic backgrounds, religious beliefs, economic status, parenting styles, rural upbringing versus urban or suburban-there are hundreds of cultural differences that individually and in endless combinations influence our conceptions of fairness, how we categorize things, our method of judging and decision making, and our deeply held beliefs about the nature of the self, among other aspects of our psychological makeup.

We are just at the beginning of learning how these fine-grained cultural differences affect our thinking. Recent research has shown that people in "tight" cultures, those with strong norms and low tolerance for deviant behavior (think India, Malaysia, and Pakistan), develop higher impulse control and more self-monitoring abilities than those from other places. Men raised in the honor culture of the American South have been shown to experience much larger surges of testosterone after insults than do Northerners. Research published late last year suggested psychological differences at the city level too. Compared to San Franciscans, Bostonians' internal sense of self-worth is more dependent on community status and financial and educational achievement. "A cultural difference doesn't have to be big to be important," Norenzayan said. "We're not just talking about comparing New York yuppies to the Dani tribesmen of Papua New Guinea."

As Norenzayan sees it, the last few generations of psychologists have suffered from "physics envy," and they need to get over it. The job, experimental psychologists often assumed, was to push past the content of people's thoughts and see the underlying universal hardware at work. "This is a deeply flawed way of studying human nature," Norenzayan told me, "because the content of our thoughts and their process are intertwined." In other words, if human cognition is shaped by cultural ideas and behavior, it can't be studied without taking into account what those ideas and behaviors are and how they are different from place to place.

This new approach suggests the possibility of reverse-engineering psychological research: look at cultural content first; cognition and behavior second. Norenzayan's recent work on religious belief is perhaps the best example of the intellectual landscape that is now open for study. When Norenzayan became a student of psychology in 1994, four years after his family had moved from Lebanon to America, he was excited to study the effect of religion on human psychology. "I remember opening textbook after textbook and turning to the index and looking for the word 'religion,' " he told me, "Again and again the very word wouldn't be listed. This was shocking. How could psychology be the science of human behavior and have nothing to say about religion? Where I grew up you'd have to be in a coma not to notice the importance of religion on how people perceive themselves and the world around them."

Norenzayan became interested in how certain religious beliefs, handed down through generations, may have shaped human psychology to make possible the creation of large-scale societies. He has suggested that there may be a connection between the growth of religions that believe in "morally concerned deities"-that is, a god or gods who care if people are good or bad-and the evolution of large cities and nations. To be cooperative in large groups of relative strangers, in other words, might have required the shared belief that an all-powerful being was forever watching over your shoulder.

If religion was necessary in the development of large-scale societies, can large-scale societies survive without religion? Norenzayan points to parts of Scandinavia with atheist majorities that seem to be doing just fine. They may have climbed the ladder of religion and effectively kicked it away. Or perhaps, after a thousand years of religious belief, the idea of an unseen entity always watching your behavior remains in our culturally shaped thinking even after the belief in God dissipates or disappears.

Why, I asked Norenzayan, if religion might have been so central to human psychology, have researchers not delved into the topic? "Experimental psychologists are the weirdest of the weird," said Norenzayan. "They are almost the least religious academics, next to biologists. And because academics mostly talk amongst themselves, they could look around and say, 'No one who is important to me is religious, so this must not be very important.'" Indeed, almost every major theorist on human behavior in the last 100 years predicted that it was just a matter of time before religion was a vestige of the past. But the world persists in being a very religious place.

Henrich, Heine, and Norenzayan's fear of being ostracized after the publication of the WEIRD paper turned out to be misplaced. Response to the paper, both published and otherwise, has been nearly universally positive, with more than a few of their colleagues suggesting that the work will spark fundamental changes. "I have no doubt that this paper is going to change the social sciences," said Richard Nisbett, an eminent psychologist at the University of Michigan. "It just puts it all in one place and makes such a bold statement."

More remarkable still, after reading the paper, academics from other disciplines began to come forward with their own mea culpas. Commenting on the paper, two brain researchers from Northwestern University argued (pdf) that the nascent field of neuroimaging had made the same mistake as psychologists, noting that 90 percent of neuroimaging studies were performed in Western countries. Researchers in motor development similarly suggested that their discipline's body of research ignored how different child-rearing practices around the world can dramatically influence states of development. Two psycholinguistics professors suggested that their colleagues had also made the same mistake: blithely assuming human homogeneity while focusing their research primarily on one rather small slice of humanity.

At its heart, the challenge of the WEIRD paper is not simply to the field of experimental human research (do more cross-cultural studies!); it is a challenge to our Western conception of human nature. For some time now, the most widely accepted answer to the question of why humans, among all animals, have so successfully adapted to environments across the globe is that we have big brains with the ability to learn, improvise, and problem-solve.

Henrich has challenged this "cognitive niche" hypothesis with the "cultural niche" hypothesis. He notes that the amount of knowledge in any culture is far greater than the capacity of individuals to learn or figure it all out on their own. He suggests that individuals tap that cultural storehouse of knowledge simply by mimicking (often unconsciously) the behavior and ways of thinking of those around them. We shape a tool in a certain manner, adhere to a food taboo, or think about fairness in a particular way, not because we individually have figured out that behavior's adaptive value, but because we instinctively trust our culture to show us the way. When Henrich asked Fijian women why they avoided certain potentially toxic fish during pregnancy and breastfeeding, he found that many didn't know or had fanciful reasons. Regardless of their personal understanding, by mimicking this culturally adaptive behavior they were protecting their offspring. The unique trick of human psychology, these researchers suggest, might be this: our big brains are evolved to let local culture lead us in life's dance.

The applications of this new way of looking at the human mind are still in the offing. Henrich suggests that his research about fairness might first be applied to anyone working in international relations or development. People are not "plug and play," as he puts it, and you cannot expect to drop a Western court system or form of government into another culture and expect it to work as it does back home. Those trying to use economic incentives to encourage sustainable land use will similarly need to understand local notions of fairness to have any chance of influencing behavior in predictable ways.

Because of our peculiarly Western way of thinking of ourselves as independent of others, this idea of the culturally shaped mind doesn't go down very easily. Perhaps the richest and most established vein of cultural psychology-that which compares Western and Eastern concepts of the self-goes to the heart of this problem. Heine has spent much of his career following the lead of a seminal paper published in 1991 by Hazel Rose Markus, of Stanford University, and Shinobu Kitayama, who is now at the University of Michigan. Markus and Kitayama suggested that different cultures foster strikingly different views of the self, particularly along one axis: some cultures regard the self as independent from others; others see the self as interdependent. The interdependent self-which is more the norm in East Asian countries, including Japan and China-connects itself with others in a social group and favors social harmony over self-expression. The independent self-which is most prominent in America-focuses on individual attributes and preferences and thinks of the self as existing apart from the group.

The classic "rod and frame" task: Is the line in the center vertical?

That we in the West develop brains that are wired to see ourselves as separate from others may also be connected to differences in how we reason, Heine argues. Unlike the vast majority of the world, Westerners (and Americans in particular) tend to reason analytically as opposed to holistically. That is, the American mind strives to figure out the world by taking it apart and examining its pieces. Show a Japanese and an American the same cartoon of an aquarium, and the American will remember details mostly about the moving fish while the Japanese observer will likely later be able to describe the seaweed, the bubbles, and other objects in the background. Shown another way, in a different test analytic Americans will do better on something called the "rod and frame" task, where one has to judge whether a line is vertical even though the frame around it is skewed. Americans see the line as apart from the frame, just as they see themselves as apart from the group.

Heine and others suggest that such differences may be the echoes of cultural activities and trends going back thousands of years. Whether you think of yourself as interdependent or independent may depend on whether your distant ancestors farmed rice (which required a great deal of shared labor and group cooperation) or herded animals (which rewarded individualism and aggression). Heine points to Nisbett at Michigan, who has argued (pdf) that the analytic/holistic dichotomy in reasoning styles can be clearly seen, respectively, in Greek and Chinese philosophical writing dating back 2,500 years. These psychological trends and tendencies may echo down generations, hundreds of years after the activity or situation that brought them into existence has disappeared or fundamentally changed.

And here is the rub: the culturally shaped analytic/individualistic mind-sets may partly explain why Western researchers have so dramatically failed to take into account the interplay between culture and cognition. In the end, the goal of boiling down human psychology to hardwiring is not surprising given the type of mind that has been designing the studies. Taking an object (in this case the human mind) out of its context is, after all, what distinguishes the analytic reasoning style prevalent in the West. Similarly, we may have underestimated the impact of culture because the very ideas of being subject to the will of larger historical currents and of unconsciously mimicking the cognition of those around us challenges our Western conception of the self as independent and self-determined. The historical missteps of Western researchers, in other words, have been the predictable consequences of the WEIRD mind doing the thinking.

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Why Americans Are the Weirdest People in the World

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In the Summer of 1995, a young graduate student in anthropology at UCLA named Joe Henrich traveled to Peru to carry out some fieldwork among the Machiguenga, an indigenous people who live north of Machu Picchu in the Amazon basin.

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Quick look (QL): "You often assume or take things for granted that you do not ordinarily know to be the case."

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It is the biggest of problems, it is the smallest of problems. At present physicists have two separate rulebooks explaining how nature works. There is general relativity, which beautifully accounts for gravity and all of the things it dominates: orbiting planets, colliding galaxies, the dynamics of the expanding universe as a whole. That's big. Then there is quantum mechanics, which handles the other three forces - electromagnetism and the two nuclear forces. Quantum theory is extremely adept at describing what happens when a uranium atom decays, or when individual particles of light hit a solar cell. That's small.

Now for the problem: relativity and quantum mechanics are fundamentally different theories that have different formulations. It is not just a matter of scientific terminology; it is a clash of genuinely incompatible descriptions of reality.

The conflict between the two halves of physics has been brewing for more than a century - sparked by a pair of 1905 papers by Einstein, one outlining relativity and the other introducing the quantum - but recently it has entered an intriguing, unpredictable new phase. Two notable physicists have staked out extreme positions in their camps, conducting experiments that could finally settle which approach is paramount.

Basically you can think of the division between the relativity and quantum systems as "smooth" versus "chunky". In general relativity, events are continuous and deterministic, meaning that every cause matches up to a specific, local effect. In quantum mechanics, events produced by the interaction of subatomic particles happen in jumps (yes, quantum leaps), with probabilistic rather than definite outcomes. Quantum rules allow connections forbidden by classical physics. This was demonstrated in a much-discussed recent experiment in which Dutch researchers defied the local effect. They showed that two particles - in this case, electrons - could influence each other instantly, even though they were a mile apart. When you try to interpret smooth relativistic laws in a chunky quantum style, or vice versa, things go dreadfully wrong.

Relativity gives nonsensical answers when you try to scale it down to quantum size, eventually descending to infinite values in its description of gravity. Likewise, quantum mechanics runs into serious trouble when you blow it up to cosmic dimensions. Quantum fields carry a certain amount of energy, even in seemingly empty space, and the amount of energy gets bigger as the fields get bigger. According to Einstein, energy and mass are equivalent (that's the message of E=mc ²), so piling up energy is exactly like piling up mass. Go big enough, and the amount of energy in the quantum fields becomes so great that it creates a black hole that causes the universe to fold in on itself. Oops.

Craig Hogan, a theoretical astrophysicist at the University of Chicago and the director of the Center for Particle Astrophysics at Fermilab, is reinterpreting the quantum side with a novel theory in which the quantum units of space itself might be large enough to be studied directly. Meanwhile, Lee Smolin, a founding member of the Perimeter Institute for Theoretical Physics in Waterloo, Canada, is seeking to push physics forward by returning to Einstein's philosophical roots and extending them in an exciting direction.

To understand what is at stake, look back at the precedents. When Einstein unveiled general relativity, he not only superseded Isaac Newton's theory of gravity; he also unleashed a new way of looking at physics that led to the modern conception of the Big Bang and black holes, not to mention atomic bombs and the time adjustments essential to your phone's GPS. Likewise, quantum mechanics did much more than reformulate James Clerk Maxwell's textbook equations of electricity, magnetism and light. It provided the conceptual tools for the Large Hadron Collider, solar cells, all of modern microelectronics.

What emerges from the dust-up could be nothing less than a third revolution in modern physics, with staggering implications. It could tell us where the laws of nature came from, and whether the cosmos is built on uncertainty or whether it is fundamentally deterministic, with every event linked definitively to a cause.

Small is beautiful

Hogan, champion of the quantum view, is what you might call a lamp-post physicist: rather than groping about in the dark, he prefers to focus his efforts where the light is bright, because that's where you are most likely to be able to see something interesting. That's the guiding principle behind his current research. The clash between relativity and quantum mechanics happens when you try to analyse what gravity is doing over extremely short distances, he notes, so he has decided to get a really good look at what is happening right there. "I'm betting there's an experiment we can do that might be able to see something about what's going on, about that interface that we still don't understand," he says.

A basic assumption in Einstein's physics - an assumption going all the way back to Aristotle, really - is that space is continuous and infinitely divisible, so that any distance could be chopped up into even smaller distances. But Hogan questions whether that is really true. Just as a pixel is the smallest unit of an image on your screen and a photon is the smallest unit of light, he argues, so there might be an unbreakable smallest unit of distance: a quantum of space.

Chunky space does not neatly align with the ideas in string theory - or in any other proposed physics model

In Hogan's scenario, it would be meaningless to ask how gravity behaves at distances smaller than a single chunk of space. There would be no way for gravity to function at the smallest scales because no such scale would exist. Or put another way, general relativity would be forced to make peace with quantum physics, because the space in which physicists measure the effects of relativity would itself be divided into unbreakable quantum units. The theatre of reality in which gravity acts would take place on a quantum stage.

Hogan acknowledges that his concept sounds a bit odd, even to a lot of his colleagues on the quantum side of things. Since the late 1960s, a group of physicists and mathematicians have been developing a framework called string theory to help reconcile general relativity with quantum mechanics; over the years, it has evolved into the default mainstream theory, even as it has failed to deliver on much of its early promise. Like the chunky-space solution, string theory assumes a fundamental structure to space, but from there the two diverge. String theory posits that every object in the universe consists of vibrating strings of energy. Like chunky space, string theory averts gravitational catastrophe by introducing a finite, smallest scale to the universe, although the unit strings are drastically smaller even than the spatial structures Hogan is trying to find.

Chunky space does not neatly align with the ideas in string theory - or in any other proposed physics model, for that matter. "It's a new idea. It's not in the textbooks; it's not a prediction of any standard theory," Hogan says, sounding not the least bit concerned. "But there isn't any standard theory, right?"

If he is right about the chunkiness of space, that would knock out a lot of the current formulations of string theory and inspire a fresh approach to reformulating general relativity in quantum terms. It would suggest new ways to understand the inherent nature of space and time. And weirdest of all, perhaps, it would bolster the notion that our seemingly three-dimensional reality is composed of more basic, two-dimensional units. Hogan takes the "pixel" metaphor seriously: just as a TV picture can create the impression of depth from a bunch of flat pixels, he suggests, so space itself might emerge from a collection of elements that act as if they inhabit only two dimensions.

Like many ideas from the far edge of today's theoretical physics, Hogan's speculations can sound suspiciously like late-night philosophising in the freshman dorm. What makes them drastically different is that he plans to put them to a hard experimental test. As in, right now.

Starting in 2007, Hogan began thinking about how to build a device that could measure the exceedingly fine graininess of space. As it turns out, his colleagues had plenty of ideas about how to do that, drawing on technology developed to search for gravitational waves. Within two years Hogan had put together a proposal and was working with collaborators at Fermilab, the University of Chicago and other institutions to build a chunk-detecting machine, which he more elegantly calls a "holometer". (The name is an esoteric pun, referencing both a 17th-century surveying instrument and the theory that 2D space could appear three-dimensional, analogous to a hologram.)

Beneath its layers of conceptual complexity, the holometer is technologically little more than a laser beam, a half-reflective mirror to split the laser into two perpendicular beams, and two other mirrors to bounce those beams back along a pair of 40m-long tunnels. The beams are calibrated to register the precise locations of the mirrors. If space is chunky, the locations of the mirrors would constantly wander about (strictly speaking, space itself is doing the wandering), creating a constant, random variation in their separation. When the two beams are recombined, they'd be slightly out of sync, and the amount of the discrepancy would reveal the scale of the chunks of space.

For the scale of chunkiness that Hogan hopes to find, he needs to measure distances to an accuracy of 10⁻¹⁸ m, about 100m times smaller than a hydrogen atom, and collect data at a rate of about 100m readings per second. Amazingly, such an experiment is not only possible, but practical. "We were able to do it pretty cheaply because of advances in photonics, a lot of off-the-shelf parts, fast electronics and things like that," Hogan says. "It's a pretty speculative experiment, so you wouldn't have done it unless it was cheap." The holometer is currently humming away, collecting data at the target accuracy; he expects to have preliminary readings by the end of the year.

Hogan has his share of fierce sceptics, including many within the theoretical physics community. The reason for the disagreement is easy to appreciate: a success for the holometer would mean failure for a lot of the work being done in string theory. Despite this superficial sparring, though, Hogan and most of his theorist colleagues share a deep core conviction: they broadly agree that general relativity will ultimately prove subordinate to quantum mechanics. The other three laws of physics follow quantum rules, so it makes sense that gravity must as well.

For most of today's theorists, however, belief in the primacy of quantum mechanics runs deeper still. At a philosophical - epistemological - level, they regard the large-scale reality of classical physics as a kind of illusion, an approximation that emerges from the more "true" aspects of the quantum world operating at an extremely small scale. Chunky space certainly aligns with that worldview.

Hogan likens his project to the landmark Michelson-Morley experiment of the 19th century, which searched for the aether - the hypothetical substance of space that, according to the leading theory of the time, transmitted light waves through a vacuum. The experiment found nothing; that perplexing null result helped inspire Einstein's special theory of relativity, which in turn spawned the general theory of relativity and eventually turned the entire world of physics upside down. Adding to the historical connection, the Michelson-Morley experiment also measured the structure of space using mirrors and a split beam of light, following a setup remarkably similar to Hogan's.

"We're doing the holometer in that kind of spirit. If we don't see something or we do see something, either way it's interesting. The reason to do the experiment is just to see whether we can find something to guide the theory," Hogan says. "You find out what your theorist colleagues are made of by how they react to this idea. There's a world of very mathematical thinking out there. I'm hoping for an experimental result that forces people to focus the theoretical thinking in a different direction."

Whether or not he finds his quantum structure of space, Hogan is confident the holometer will help physics address its big-small problem. It will show the right way (or rule out the wrong way) to understand the underlying quantum structure of space and how that affects the relativistic laws of gravity flowing through it.

A bigger vision

If you are looking for a totally different direction, Smolin of the Perimeter Institute is your man. Where Hogan goes gently against the grain, Smolin is a full-on dissenter: "There's a thing that Richard Feynman told me when I was a graduate student. He said, approximately, 'If all your colleagues have tried to demonstrate that something's true and failed, it might be because that thing is not true.' Well, string theory has been going for 40 or 50 years without definitive progress."

And that is just the start of a broader critique. Smolin thinks the small-scale approach to physics is inherently incomplete. Current versions of quantum field theory do a fine job explaining how individual particles or small systems of particles behave, but they fail to take into account what is needed to have a sensible theory of the cosmos as a whole. They don't explain why reality is like this, and not like something else. In Smolin's terms, quantum mechanics is merely "a theory of subsystems of the universe".

A more fruitful path forward, he suggests, is to consider the universe as a single enormous system, and to build a new kind of theory that can apply to the whole thing. And we already have a theory that provides a framework for that approach: general relativity. Unlike the quantum framework, general relativity allows no place for an outside observer or external clock, because there is no "outside". Instead, all of reality is described in terms of relationships between objects and between different regions of space. Even something as basic as inertia (the resistance of your car to move until forced to by the engine, and its tendency to keep moving after you take your foot off the accelerator) can be thought of as connected to the gravitational field of every other particle in the universe.

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'What if the universe were entirely empty except for two astronauts, one of them spinning, the other stationary?' Photograph: Nasa/Reuters

That last statement is strange enough that it's worth pausing for a moment to consider it more closely. Consider a thought problem, closely related to the one that originally led Einstein to this idea in 1907. What if the universe were entirely empty except for two astronauts? One of them is spinning, the other is stationary. The spinning one feels dizzy, doing cartwheels in space. But which one of the two is spinning? From either astronaut's perspective, the other is the one spinning. Without any external reference, Einstein argued, there is no way to say which one is correct, and no reason why one should feel an effect different from what the other experiences.

The distinction between the two astronauts makes sense only when you reintroduce the rest of the universe. In the classic interpretation of general relativity, then, inertia exists only because you can measure it against the entire cosmic gravitational field. What holds true in that thought problem holds true for every object in the real world: the behaviour of each part is inextricably related to that of every other part. If you've ever felt as if you wanted to be a part of something big, well, this is the right kind of physics for you. It is also, Smolin thinks, a promising way to obtain bigger answers about how nature really works, across all scales.

"General relativity is not a description of subsystems. It is a description of the whole universe as a closed system," he says. When physicists are trying to resolve the clash between relativity and quantum mechanics, therefore, it seems like a smart strategy for them to follow Einstein's lead and go as big as they possibly can.

Smolin is keenly aware that he is pushing against the prevailing devotion to small-scale, quantum-style thinking. "I don't mean to stir things up; it just kind of happens that way. My role is to think clearly about these difficult issues, put my conclusions out there, and let the dust settle," he says genially. "I hope people will engage with the arguments, but I really hope that the arguments lead to testable predictions."

At first blush, Smolin's ideas sound like a formidable starting point for concrete experimentation. Much as all of the parts of the universe are linked across space, they may also be linked across time, he suggests. His arguments led him to hypothesise that the laws of physics evolve over the history of the universe. Over the years, he has developed two detailed proposals for how this might happen. His theory of cosmological natural selection, which he hammered out in the 1990s, envisions black holes as cosmic eggs that hatch new universes. More recently, he has developed a provocative hypothesis about the emergence of the laws of quantum mechanics, called the principle of precedence - and this one seems much more readily put to the test.

Smolin's principle of precedence arises as an answer to the question of why physical phenomena are reproducible. If you perform an experiment that has been performed before, you expect the outcome will be the same as in the past. (Strike a match and it bursts into flame; strike another match the same way and... you get the idea.) Reproducibility is such a familiar part of life that we typically don't even think about it. We simply attribute consistent outcomes to the action of a natural "law" that acts the same way at all times. Smolin hypothesises that those laws actually may emerge over time, as quantum systems copy the behaviour of similar systems in the past.

One possible way to catch emergence in the act is by running an experiment that has never been done before, so there is no past version (that is, no precedent) for it to copy. Such an experiment might involve the creation of a highly complex quantum system, containing many components that exist in a novel entangled state. If the principle of precedence is correct, the initial response of the system will be essentially random. As the experiment is repeated, however, precedence builds up and the response should become predictable... in theory. "A system by which the universe is building up precedent would be hard to distinguish from the noises of experimental practice," Smolin concedes, "but it's not impossible."

Although precedence can play out at the atomic scale, its influence would be system-wide, cosmic. It ties back to Smolin's idea that small-scale, reductionist thinking seems like the wrong way to solve the big puzzles. Getting the two classes of physics theories to work together, though important, is not enough, either. What he wants to know - what we all want to know - is why the universe is the way it is. Why does time move forward and not backward? How did we end up here, with these laws and this universe, not some others?

The present lack of any meaningful answer to those questions reveals "something deeply wrong with our understanding of quantum field theory", Smolin says. Like Hogan, he is less concerned about the outcome of any one experiment than he is with the larger programme of seeking fundamental truths. For Smolin, that means being able to tell a complete, coherent story about the universe; it means being able to predict experiments, but also to explain the unique properties that made atoms, planets, rainbows and people. Here again he draws inspiration from Einstein.

"The lesson of general relativity, again and again, is the triumph of relationalism," Smolin says. The most likely way to get the big answers is to engage with the universe as a whole.

And the winner is?

If you wanted to pick a referee in the big-small debate, you could hardly do better than Sean Carroll, an expert in cosmology, field theory and gravitational physics at Caltech. He knows his way around relativity, he knows his way around quantum mechanics, and he has a healthy sense of the absurd: he calls his personal blog Preposterous Universe. Right off the bat, Carroll awards most of the points to the quantum side. "Most of us in this game believe that quantum mechanics is much more fundamental than general relativity is," he says. That has been the prevailing view ever since the 1920s, when Einstein tried and repeatedly failed to find flaws in the counterintuitive predictions of quantum theory. The recent Dutch experiment demonstrating an instantaneous quantum connection between two widely separated particles - the kind of event that Einstein derided as "spooky action at a distance" - only underscores the strength of the evidence.

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Illustration by Owen Gildersleeve

Taking a larger view, the real issue is not general relativity versus quantum field theory, Carroll explains, but classical dynamics versus quantum dynamics. Relativity, despite its perceived strangeness, is classical in how it regards cause and effect; quantum mechanics most definitely is not. Einstein was optimistic that some deeper discoveries would uncover a classical, deterministic reality hiding beneath quantum mechanics, but no such order has yet been found. The demonstrated reality of spooky action at a distance argues that such order does not exist.

"If anything, people underappreciate the extent to which quantum mechanics just completely throws away our notions of space and locality [the notion that a physical event can affect only its immediate surroundings]. Those things simply are not there in quantum mechanics," Carroll says. They may be large-scale impressions that emerge from very different small-scale phenomena, like Hogan's argument about 3D reality emerging from 2D quantum units of space.

Despite that seeming endorsement, Carroll regards Hogan's holometer as a long shot, though he admits it is removed from his area of research. At the other end, he doesn't think much of Smolin's efforts to start with space as a fundamental thing; he believes the notion is as absurd as trying to argue that air is more fundamental than atoms. As for what kind of quantum system might take physics to the next level, Carroll remains broadly optimistic about string theory, which he says "seems to be a very natural extension of quantum field theory". In all these ways, he is true to the mainstream, quantum-based thinking in modern physics.

Yet Carroll's ruling, while almost entirely pro-quantum, is not purely an endorsement of small-scale thinking. There are still huge gaps in what quantum theory can explain. "Our inability to figure out the correct version of quantum mechanics is embarrassing," he says. "And our current way of thinking about quantum mechanics is simply a complete failure when you try to think about cosmology or the whole universe. We don't even know what time is." Both Hogan and Smolin endorse this sentiment, although they disagree about what to do in response. Carroll favours a bottom-up explanation in which time emerges from small-scale quantum interactions, but declares himself "entirely agnostic" about Smolin's competing suggestion that time is more universal and fundamental. In the case of time, then, the jury is still out.

No matter how the theories shake out, the large scale is inescapably important, because it is the world we inhabit and observe. In essence, the universe as a whole is the answer, and the challenge to physicists is to find ways to make it pop out of their equations. Even if Hogan is right, his space-chunks have to average out to the smooth reality we experience every day. Even if Smolin is wrong, there is an entire cosmos out there with unique properties that need to be explained - something that, for now at least, quantum physics alone cannot do.

By pushing at the bounds of understanding, Hogan and Smolin are helping the field of physics make that connection. They are nudging it toward reconciliation not just between quantum mechanics and general relativity, but between idea and perception. The next great theory of physics will undoubtedly lead to beautiful new mathematics and unimaginable new technologies. But the best thing it can do is create deeper meaning that connects back to us, the observers, who get to define ourselves as the fundamental scale of the universe.

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* This essay originally appeared in issue 29 of Nautilus. To find out more, visit
* Follow the Long Read on Twitter at @gdnlongread, or sign up to the long read weekly email here.

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Relativity v quantum mechanics - the battle for the universe

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It is the biggest of problems, it is the smallest of problems. At present physicists have two separate rulebooks explaining how nature works. There is general relativity, which beautifully accounts for gravity and all of the things it dominates: orbiting planets, colliding galaxies, the dynamics of the expanding universe as a whole.

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“Without the assumption of the existence of uniformities there can be no knowledge.” Discuss this claim with reference to two areas of knowledge.

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“Without the assumption of the existence of uniformities there can be no knowledge.” Discuss this claim with reference to two areas of knowledge.

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QL: "Most if not all the statements of a theory
are generalized conditionals, which place no restrictions on the type of phenomena they may explain."

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Ernest Nagel, Assumptions in Economic Theory, The American Economic Review, Vol. 53, No. 2, Papers and Proceedings of the Seventy-Fifth Annual Meeting of the American Economic Association (May, 1963), pp. 211-219

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Are we in control of our decisions? | Dan Ariely

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Uniformitarianism, also known as the Doctrine of Uniformity, is the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere.

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Making sense of string theory | Brian Greene

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http://www.ted.com In clear, nontechnical language, string theorist Brian Greene explains how our understanding of the universe has evolved from Einstein's notions of gravity and space-time to superstring theory, where minuscule strands of energy vibrating in 11 dimensions create every particle and force in the universe.

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One of the great advantages of being a Jesuit astronomer at the Vatican Observatory is that, since we are supported by the Church, we don't have to worry about writing proposals, sitting on committees or even teaching classes. We can concentrate on doing interesting, long-term scientific projects.

Of course, we do have our own personal commitments. I live in a community of a dozen Jesuit priests and brothers (most of us with doctorates in astronomy or related fields), and as a community we care for each other... picking up a fellow Jesuit at the airport, or taking an elderly brother to a doctor's appointment. But generally our vow of celibacy means that we're free to go where the work calls us, whether it's traveling to conferences or staying late in the lab. We don't have to worry about a child with the flu or a spouse's job search.

There is one call on our time, however, that my married colleagues don't face. It's the emails and letters we receive, regularly, asking us about our lives of science and faith.

Of course, the whole reason the Vatican established a Vatican Observatory was to show the world that the Church supports science. Answering that constant stream of questions is an essential way we "show the world," even if it is just one letter at a time.

To try to reach more people, my colleague Paul Mueller and I have just written a book that addresses some of the most frequently asked questions. In Would You Baptize an Extraterrestrial? we try to give more space than just an email reply to issues ranging from the Big Bang or Galileo to the Star of Bethlehem and, yes, the what-if of extraterrestrial intelligence.

Behind all those questions, of course, is the puzzle that some people have seeing religious people as scientists. Mind you, a lot of techies are also churchgoers (a topic of an earlier book of mine, God's Mechanics). But if you've never gotten to know a scientist, you may not have seen how religion and science actually work together in practice.

Typically, the argument we hear runs something like this: Science is all about finding and evaluating evidence for things, right? So what evidence is there that the Bible is correct about a Creator? And why is that evidence any more compelling than other religion's stories?

But notice what that question assumes. It acts as if the big questions of life -- Love, Beauty, God -- can be solved with the kind of answer you'd find in the back of a physics book. But Love is not a puzzle that can be "solved" with "evidence"; it is a reality that grows, in beauty and complexity, the longer you live with it.

Even worse, that way of asking the question presumes that God is something you can finally arrive at on the basis of "evidence." Besides the obvious fact that evidence can be misleading -- we tend to find only what we expect to see -- God is not something that comes at the end of a logical train of thought. Rather, my faith in God is my basic foundational assumption, the axiom that I start with when I do my logic. In fact, mathematicians remind us that all logical systems require starting assumptions. What you conclude, depends a lot on what you assume.

So what do I assume?

I assume we live in a real universe -- we're not in the Matrix, or figments in the imagination of some computer gamer.

I assume that this is a logical universe that operates by laws -- it's not the universe of pagan nature gods who did everything by whim, but rather a universe that can be rationally understood and whose behavior can be reliably predicted once we begin to figure it out.

Finally, I assume that I live in a universe that is ultimately good and beautiful and worthy of spending my life to study it.

Notice, those are all religious assumptions. There are other religions that might teach that "all is illusion" or that the universe is inherently corrupt and evil; other religions might rely on nature gods to explain all the things that puzzle us. But those aren't my religion.

I believe that the physical universe we study was was made deliberately by God who found it good -- and who makes Himself known in the things He created (to quote St. Paul). Thus scientific truth is a pathway to God. Even a scientist who denies the existence of any creator God must nonetheless worship at the altar of Truth, or else that science is worthless.

And why, at the end of the day, do I choose one religion over another? I can accept that all religions ultimately are looking for the same God. But I suspect that some religions do a better job of it than others... just as Newton's physics was an improvement over the medieval view, and quantum physics picks up where Newton's version fails. The religions of The Book -- Judaism, Christianity, Islam -- all recognize a God outside of nature who created this universe and found it good. Of these, I adopt the Catholic view because to me it is the most complete, most coherent vision of God and God's interaction with our universe.

I find that my religion's understanding of the universe is consistent with everything that I observe about life: not only in science, but in my experience of beauty, love and all the other transcendentals that science does not treat... including those experiences that I interpret as prayer, my direct experience of God.

It's not a proof. But it is a consistency argument. Your mileage may vary.

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Science, Religion and the Assumptions We Make

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One of the great advantages of being a Jesuit astronomer at the Vatican Observatory is that, since we are supported by the Church, we don't have to worry about writing proposals, sitting on committees or even teaching classes. We can concentrate on doing interesting, long-term scientific projects.

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To be skilled in critical thinking is to be able to take one's thinking apart systematically, to analyze each part, assess it for quality and then improve it. The first step in this process is understanding the parts of thinking, or elements of reasoning.

These elements are: purpose, question, information, inference, assumption, point of view, concepts, and implications. They are present in the mind whenever we reason. To take command of our thinking, we need to formulate both our purpose and the question at issue clearly. We need to use information in our thinking that is both relevant to the question we are dealing with, and accurate. We need to make logical inferences based on sound assumptions. We need to understand our own point of view and fully consider other relevant viewpoints. We need to use concepts justifiably and follow out the implications of decisions we are considering. (For an elaboration of the Elements of Reasoning, see a Miniature Guide to the Foundations of Analytic Thinking.)

In this article we focus on two of the elements of reasoning: inferences and assumptions. Learning to distinguish inferences from assumptions is an important intellectual skill. Many confuse the two elements. Let us begin with a review of the basic meanings:

1. Inference: An inference is a step of the mind, an intellectual act by which one concludes that something is true in light of something else's being true, or seeming to be true. If you come at me with a knife in your hand, I probably would infer that you mean to do me harm. Inferences can be accurate or inaccurate, logical or illogical, justified or unjustified.

2. Assumption: An assumption is something we take for granted or presuppose. Usually it is something we previously learned and do not question. It is part of our system of beliefs. We assume our beliefs to be true and use them to interpret the world about us. If we believe that it is dangerous to walk late at night in big cities and we are staying in Chicago, we will infer that it is dangerous to go for a walk late at night. We take for granted our belief that it is dangerous to walk late at night in big cities. If our belief is a sound one, our assumption is sound. If our belief is not sound, our assumption is not sound. Beliefs, and hence assumptions, can be unjustified or justified, depending upon whether we do or do not have good reasons for them. Consider this example: "I heard a scratch at the door. I got up to let the cat in." My inference was based on the assumption (my prior belief) that only the cat makes that noise, and that he makes it only when he wants to be let in.

We humans naturally and regularly use our beliefs as assumptions and make inferences based on those assumptions. We must do so to make sense of where we are, what we are about, and what is happening. Assumptions and inferences permeate our lives precisely because we cannot act without them. We make judgments, form interpretations, and come to conclusions based on the beliefs we have formed.

If you put humans in any situation, they start to give it some meaning or other. People automatically make inferences to gain a basis for understanding and action. So quickly and automatically do we make inferences that we do not, without training, notice them as inferences. We see dark clouds and infer rain. We hear the door slam and infer that someone has arrived. We see a frowning face and infer that the person is upset. If our friend is late, we infer that she is being inconsiderate. We meet a tall guy and infer that he is good at basketball, an Asian and infer that she will be good at math. We read a book, and interpret what the various sentences and paragraphs - indeed what the whole book - is saying. We listen to what people say and make a series of inferences as to what they mean.

As we write, we make inferences as to what readers will make of what we are writing. We make inferences as to the clarity of what we are saying, what requires further explanation, what has to be exemplified or illustrated, and what does not. Many of our inferences are justified and reasonable, but some are not.

As always, an important part of critical thinking is the art of bringing what is subconscious in our thought to the level of conscious realization. This includes the recognition that our experiences are shaped by the inferences we make during those experiences. It enables us to separate our experiences into two categories: the raw data of our experience in contrast with our interpretations of those data, or the inferences we are making about them. Eventually we need to realize that the inferences we make are heavily influenced by our point of view and the assumptions we have made about people and situations. This puts us in the position of being able to broaden the scope of our outlook, to see situations from more than one point of view, and hence to become more open-minded.

Often different people make different inferences because they bring to situations different viewpoints. They see the data differently. To put it another way, they make different assumptions about what they see. For example, if two people see a man lying in a gutter, one might infer, "There's a drunken bum." The other might infer, "There's a man in need of help." These inferences are based on different assumptions about the conditions under which people end up in gutters. Moreover, these assumptions are connected to each person's viewpoint about people. The first person assumes, "Only drunks are to be found in gutters." The second person assumes, "People lying in the gutter are in need of help."

The first person may have developed the point of view that people are fundamentally responsible for what happens to them and ought to be able to care for themselves. The second may have developed the point of view that the problems people have are often caused by forces and events beyond their control. The reasoning of these two people, in terms of their inferences and assumptions, could be characterized in the following way:

Critical thinkers notice the inferences they are making, the assumptions upon which they are basing those inferences, and the point of view about the world they are developing. To develop these skills, students need practice in noticing their inferences and then figuring the assumptions that lead to them.
As students become aware of the inferences they make and the assumptions that underlie those inferences, they begin to gain command over their thinking. Because all human thinking is inferential in nature, command of thinking depends on command of the inferences embedded in it and thus of the assumptions that underlie it. Consider the way in which we plan and think our way through everyday events. We think of ourselves as preparing for breakfast, eating our breakfast, getting ready for class, arriving on time, leading class discussions, grading student papers, making plans for lunch, paying bills, engaging in an intellectual discussion, and so on. We can do none of these things without interpreting our actions, giving them meanings, making inferences about what is happening.

This is to say that we must choose among a variety of possible meanings. For example, am I "relaxing" or "wasting time?" Am I being "determined" or "stubborn?" Am I "joining" a conversation or "butting in?" Is someone "laughing with me" or "laughing at me?" Am I "helping a friend" or "being taken advantage of?" Every time we interpret our actions, every time we give them a meaning, we are making one or more inferences on the basis of one or more assumptions.

As humans, we continually make assumptions about ourselves, our jobs, our mates, our students, our children, the world in general. We take some things for granted simply because we can't question everything. Sometimes we take the wrong things for granted. For example, I run off to the store (assuming that I have enough money with me) and arrive to find that I have left my money at home. I assume that I have enough gas in the car only to find that I have run out of gas. I assume that an item marked down in price is a good buy only to find that it was marked up before it was marked down. I assume that it will not, or that it will, rain. I assume that my car will start when I turn the key and press the gas pedal. I assume that I mean well in my dealings with others.

Humans make hundreds of assumptions without knowing it---without thinking about it. Many assumptions are sound and justifiable. Many, however, are not. The question then becomes: "How can students begin to recognize the inferences they are making, the assumptions on which they are basing those inferences, and the point of view, the perspective on the world that they are forming?"

There are many ways to foster student awareness of inferences and assumptions. For one thing, all disciplined subject-matter thinking requires that students learn to make accurate assumptions about the content they are studying and become practiced in making justifiable inferences within that content. As examples: In doing math, students make mathematical inferences based on their mathematical assumptions. In doing science, they make scientific inferences based on their scientific assumptions. In constructing historical accounts, they make historical inferences based on their historical assumptions. In each case, the assumptions students make depend on their understanding of fundamental concepts and principles.

As a matter of daily practice, then, we can help students begin to notice the inferences they are making within the content we teach. We can help them identify inferences made by authors of a textbook, or of an article we give them. Once they have identified these inferences, we can ask them to figure out the assumptions that led to those inferences. When we give them routine practice in identifying inferences and assumptions, they begin to see that inferences will be illogical when the assumptions that lead to them are not justifiable. They begin to see that whenever they make an inference, there are other (perhaps more logical) inferences they could have made. They begin to see high quality inferences as coming from good reasoning.

We can also help students think about the inferences they make in daily situations, and the assumptions that lead to those inferences. As they become skilled in identifying their inferences and assumptions, they are in a better position to question the extent to which any of their assumptions is justified. They can begin to ask questions, for example, like: Am I justified in assuming that everyone eats lunch at 12:00 noon? Am I justified in assuming that it usually rains when there are black clouds in the sky? Am I justified in assuming that bumps on the head are only caused by blows?

The point is that we all make many assumptions as we go about our daily life and we ought to be able to recognize and question them. As students develop these critical intuitions, they increasingly notice their inferences and those of others. They increasingly notice what they and others are taking for granted. They increasingly notice how their point of view shapes their experiences.

This article was adapted from the book, Critical Thinking: Tools for Taking Charge of Your Learning and Your Life, by Richard Paul and Linda Elder.

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To be skilled in critical thinking is to be able to take one's thinking apart systematically, to analyze each part, assess it for quality and then improve it. The first step in this process is understanding the parts of thinking, or elements of reasoning.

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The basic problem of economics can be summarized in one sentence: How to best satisfy unlimited wants with unlimited resources.

We can break this problem into two parts:

1. Preferences -- What we like and what we dislike.

2. Resources -- We all have limited resources. Even Warren Buffett and Bill Gates have limited resources. They have the same 24 hours in a day that we do and neither is going to live forever.

All of economics, including both microeconomics and macroeconomics, come back to this basic problem on how to use limited resources to satisfy our preferences and unlimited wants.

Rational Maximizing Behavior

In order to simply model how humans attempt to do this, we need a basic behavioral assumption. The assumption is that people attempt to maximize outcomes (that is, to do as well as possible for themselves) as defined by their preferences, given their resource constraints.

Economists refer to people who do this as exhibiting 'rational maximizing behavior'. Note that in more complex economic models that this assumption can be weakened but at a cost of added complexity.

This 'rational maximizing behavior' assumption does ​not necessarily mean that people make ex ante perfect decisions. People may be limited by the amount of information they have (e.g. 'It seemed like a good idea at the time!').

As well, 'rational maximizing behavior' says nothing about the quality or nature of people's preferences (But I enjoy hitting myself on the head with a hammer!')

Tradeoffs -- You Get What You Give

The struggle between preferences and constraints means that economists must, at their core, deal with the problem of tradeoffs.

In order to get something, we must use up some of our resources.

Examples: You give up $20 to obtain the new best seller from Amazon.com. I give up 3 hours of time to watch the Blue Jays game on T.V. ('That's three hours of my life I will never get back!')

Anything obtained has a cost. Economists have a saying for this -- "There is no such thing as a free lunch!"

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What Are The Underlying Behavioral Assumptions of Economics?

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The basic problem of economics can be summarized in one sentence: How to best satisfy unlimited wants with unlimited resources. We can break this problem into two parts: Preferences -- What we like and what we dislike. Resources -- We all have limited resources. Even Warren Buffett and Bill Gates have limited resources.

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When you look at an introductory textbook for microeconomics, it seems as though economists live in a world that barely resembles the real one. Their models are built on a series of assumptions, including that individual actors have perfect information about their choices or that subjective human values can be measured quantitatively. Some models even assume away competition, substitute goods and marketing.

Economists create these elaborate fantasies in order to apply testable theories onto an otherwise deductive social science. Without assumptions, quantitative economic models would not be able to produce any meaningful conclusions.

Science, Positivism and Deduction

In his 1953 essay titled "The Methodology of Positive Economics," Milton Friedman explained why economists need to make assumptions to provide useful predictions. Friedman understood economics couldn't use the scientific method as neatly as chemistry or physics, but he still saw the scientific method as the basis. Friedman stated economists would have to rely on "uncontrolled experience rather than on controlled experiment." He was promoting a method of logical positivism, which is a subset of epistemology.

The scientific method requires isolated variables and testing to prove causality. Economists can't possibly isolate individual variables in the real world, so they assume most of them away to create a model with some constancy. Errors are bound to happen, but most economists are OK with that as long as those errors are small enough.

Not all economists are methodological positivists. Some argue that standard models are too unrealistic to ever be relied on, and applying positivism to social sciences implies human choice is an illusion.

Economist Robert Murphy of the Institute for Energy Research, a not-for-profit organization that conducts research and analysis on the functions, operations, and government regulation of global energy markets, argues economics should be focused on logical deduction, not logical positivism. Logical deduction is the science used in philosophy, mathematics and computer science. Murphy, along with some other Austrian-school economists, contend certain economic tendencies and laws are only knowable through human reasoning. (For related reading, see: Is economics a science?)

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Why do economists build assumptions into their economic models?

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When you look at an introductory textbook for microeconomics, it seems as though economists live in a world that barely resembles the real one. Their models are built on a series of assumptions, including that individual actors have perfect information about their choices or that subjective human values can be measured quantitatively.

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What could be weirder than quantum mechanics? This physics framework is responsible for any number of bizarre phenomena-theoretical cats that are simultaneously dead and alive, particles kilometers apart that can nonetheless communicate instantaneously, and indecisive photons that somehow go two directions at once.

But it is also responsible for the technological advances that make modern life possible. Without quantum mechanics there would be no transistor, and hence no personal computer; no laser, and hence no Blu-ray players. James Kakalios, a physics professor at the University of Minnesota, wants people to understand how much quantum mechanics influences our everyday lives-but to do so people must first understand quantum mechanics.

Kakalios sets out to tackle both tasks inThe Amazing Story of Quantum Mechanics (Gotham Books, 2010), an accessible, mostly math-free treatment of one of the most complex topics in science. To keep things lively, the author intersperses illustrations and analogies from Buck Rogers stories and other classic science fiction tales. We spoke to Kakalios about his new book, what quantum mechanics has made possible, and how early sci-fi visions of the future compare with the present as we know it.

[ An edited transcript of the interview follows.]

Is the purpose of this book to expose this world of quantum mechanics that people find so mysterious and point out that it's everywhere?
That's right. In fact, the introduction is called, "Quantum physics? You're soaking in it!"

There are many excellent books about the history and the philosophical underpinnings of quantum mechanics. But there didn't seem to be many that talked about how useful quantum mechanics is. Yes, the science has weird ideas and it can be confusing. But one of the most amazing things about quantum mechanics is that you can use it correctly and productively even if you're confused by it.

I present in the introduction what I call a "workingman's view" of quantum mechanics and show how if you accept on faith three weird ideas-that light is a photon; that matter has a wavelength nature associated with its motion; and that everything, light and matter, has an intrinsic angular momentum or spin that can only have discrete values-it turns out that you can then see how lasers work. You can see how a transistor works or your computer hard drive or magnetic resonance imaging-a host of technologies that we take for granted that pretty much define our life.

There were computers before the transistor; they used vacuum tubes as logic elements. To make a more powerful computer meant that you had to have more vacuum tubes. They were big, they generated a lot of heat, they were fragile. You had to make the room and the computer very large. And so if you used vacuum tubes, only the government and a few large corporations would have the most powerful computers. You wouldn't have millions of them across the country. There would be no reason to hook them all together into an Internet, and there would be no World Wide Web.

The beautiful aspect to this is the scientists who developed this were not trying to make a cell phone; they were not trying to invent a CD player. If you went to Schrödinger in 1926 and said, "Nice equation, Erwin. What's it good for?" He's not going to say, "Well, if you want to store music in a compact digital format..."

But without the curiosity-driven understanding of how atoms behave, how they interact with each other, and how they interact with light, the world we live in would be profoundly different.

So, to take one example, how does quantum mechanics make the laser possible?
One of the most basic consequences of quantum mechanics is that there is a wave associated with the motion of all matter, including electrons in an atom. Schrödinger came up with an equation that said: "You tell me the forces acting on the electron, and I can tell you what its wave is doing at any point in space and time." And Max Born said that by manipulating this wave function that Schrödinger developed, you could tell the probability of finding the electron at any point in space and time. From that, it turns out that the electron can only have certain discrete energies inside an atom. This had been discovered experimentally; this is the source of the famous line spectrum that atoms exhibit and that accounts for why neon lights are red whereas sodium streetlights have a yellow tinge. It has to do with the line spectra of their respective elements.

But to have an actual understanding of where these discrete energies come from-that electrons and atoms can only have certain energies and no other-is one of the most amazing things about quantum mechanics. It's as though you are driving a car on a racetrack and you are only allowed to go in multiples of 10 miles per hour. When you take that and you bring many atoms together, all of those energies broaden out into a band of possible energies.

The analogy that I use is you have an auditorium with an orchestra below and a balcony above. That means to go from the orchestra to the balcony you have to absorb some energy to be promoted from the orchestra to the balcony. Now if every seat in the orchestra is filled, and you want to move from one seat to another, you can't go anywhere unless you absorb some energy and are promoted up into the balcony, where there are empty seats and you can move around. What happens in a laser is you have a little mezzanine right below the balcony. You get promoted up to the balcony but then you fall and you sit in the mezzanine. And eventually, as the mezzanine gets filled up, there's a bunch of empty seats in the orchestra, where you came from.

One person gets pushed out of the mezzanine, and because of the way they talk to each other, they all go at the same time. They release energy as they fall back from the mezzanine into the orchestra, and that energy is in the form of light. Because they are all coming from the same row of seats in the mezzanine, all the light has exactly the same color. Since they all went at the same time, they are all coherently in phase. And if you have a lot of them up in the mezzanine, you can have a very high intensity beam of single-color light. That's a laser.

And just as Schrödinger couldn't have had any idea about what his equation would be used for, the same could be said of the laser, which now allows us to have CDs and DVDs and a lot of other things.
The same goes for the transistor. It was first developed to amplify radio signals, and you had transistor radios that replaced the vacuum tubes that were being used. Now they are also used as logic elements, 1s and 0s. If you apply a voltage to a transistor you can basically open or close a gate and allow electrons to flow through or make it very difficult for electrons to flow. And so you have two different current states, high and low, that you can call a 1 or a 0. You can combine them in clever ways to do logic operations with the 1s and 0s. You can encode information. You can develop a language of the 1s and 0s and manipulate them that way.

And again, I don't think that was the first thought of the people that developed the transistor. Look at all the things that it has brought out. There are probably more transistors in a standard hospital than there are stars in the Milky Way Galaxy, when you think about all the computers and all the electronic devices that we use just for medical applications. So it really has transformed life in a very profound way.

The real superheroes of science are a small handful of people who knew they were changing physics, but I don't think they recognized that they were also changing the future.

One of the ways you keep this book lively and accessible is to use anecdotes from early science fiction. How well have those predictions held up?
The main problem is that they believed that there was going to be a revolution in energy, which would lead to jet packs, death rays and flying cars. But what we got was a revolution in information. This information age, of course, came about because of semiconductors and solid-state physics, which were enabled by quantum mechanics.

A lot of these things go back to transistors and semiconductors. Is that in your view the biggest fundamental leap that quantum mechanics allowed us to make?
More than that, even. By discerning what were the fundamental rules that govern how atoms interact with each other and how they interact with light, you also have now a fundamental understanding of chemistry. There is a reason why the atoms are arranged the way they are in the periodic table of the elements, and it comes out naturally from the Schrödinger equation when you add in the Pauli exclusion principle. There is a really deep appreciation for why the world is the way it is.

Can you imagine living in a world before quantum mechanics?
We take all these things for granted. It's like the Louis C. K. YouTube clip- everything is amazing and nobody is happy.

"Quantum" is thrown around a lot as a label for things we don't understand, and we often lump a number of phenomena into the vague category of "quantum weirdness". Is that something that you'd like to see dissipate?
I would. It's used too much as a catchall. Proposing weird and counterintuitive ideas to explain observations, developing the consequences of these ideas and testing them further, and then, if they conform with reality, accepting them is not unique to quantum mechanics. It's what we call physics.

Also, because it has a reputation for weirdness, quantum mechanics is used too much as a justification for things that have nothing to do with quantum mechanics. There is an expression, "quantum woo," where people take a personal philosophy, such as the power of positive thinking or let a smile be your umbrella, and somehow affix quantum mechanics to it to try to make it sound scientific.

And make a lot of money doing so.
Yeah. It kind of seems to me to be at the same level as using mathematical knot theory or topology to justify crossing your fingers when you're making a wish. It has about as much relevance and justification.

ABOUT THE AUTHOR(S)

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What could be weirder than quantum mechanics? This physics framework is responsible for any number of bizarre phenomena-theoretical cats that are simultaneously dead and alive, particles kilometers apart that can nonetheless communicate instantaneously, and indecisive photons that somehow go two directions at once. But it is also responsible for the technological advances that make modern life possible.

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'Opt Out' Policies Increase Organ Donation

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According to the American Transplant Foundation, 18 people die every day in the United States for want of an organ transplant, and some 122,344 people are waiting for a donated organ. Changing U.S.