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Photo by Hannah Mather, used with permission.

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On Saturday 16th May the Chocolate Trial set up stall at Leeds University's Be Curious 2026.

Thank you to the over 300 participants of the chocolate trial who took part.

We've looked at the data and have some interesting things to share with you!

If you have any questions or want to share memories of the day please feel free to leave comments on any posts.

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We wanted to know if eating chocolate makes people happy.

We asked people what their favourite kind of chocolate was, white or milk, and how happy they were feeling at the start of the trial. Then we gave them a randomly selected type of chocolate to eat. At the end of the trial we asked them again how happy they were feeling.

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On Saturday 17th May 2025 Leeds University held it's previous Be Curious event. People from all over the university got to show and discuss their research. We were very excited for the Chocolate Trial to be part of that.

For more information about Be Curious go to https://www.leeds.ac.uk/becurious/

Scroll down for the results of the 2025 Be Curious Chocolate Trial.

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395 people took part in the Chocolate Trial

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395 people took part in the Chocolate Trial

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112 adults and 283 children.

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We asked people how they were feeling before having chocolate; very happy, happy or unhappy. 

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We asked people how they were feeling before having chocolate; very happy, happy or unhappy. 

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227 said they were very happy

149 said they were happy

19 said they were unhappy

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How happy were people after they'd had their chocolate?

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How happy were people after they'd had their chocolate?

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321 people were very happy

55 people were happy

12 people were unhappy

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57% of people said they were very happy before eating chocolate.

83% of people said they were very happy after eating their preferred chocolate.

80% of people said they were very happy after eating the kind of chocolate they did not prefer.

86% of people said they were very happy after eating milk chocolate.

79% of people said they were very happy after eating white chocolate.

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DISCLAIMER - The Chocolate Trial is a public engagement activity designed to show people how clinical trials work. It is not a clinical trial and therefore does not comply with clinical trial regulations or receive any trial funding.

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249 children and 109 adults took part in the Chocolate Trial.

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235 of our participants preferred milk chocolate and 123 preferred white.

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118 of our participants were very happy, 152 were quite happy and 18 were not happy.

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272 of our participants were very happy, 76 were quite happy and 23 were not happy.

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196 participants were given milk chocolate and 175 were given white.

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147 participants were very happy, 40 were quite happy and 9 were not happy.

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125 participants were very happy, 36 were quite happy and 14 were not happy.

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244 participants got their preferred chocolate and 127 didn't.

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120 people who preferred milk chocolate and got it were very happy, 26 were quite happy and 4 were not happy.

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79 people who preferred white chocolate and got it were very happy, 10 were quite happy and 5 were not happy.

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46 people who preferred milk but got white were very happy, 26 were quite happy and 9 were not happy.

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27 people who preferred white chocolate but got milk were very happy, 14 were quite happy and 5 were not happy.

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For this trial we randomised people. This means we left it up to chance which group they ended up in. We asked them to reach into a bag and take out a ball. The colour of the ball decided what kind of chocolate they would be given.

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Our results clearly show the people are happier after they've had chocolate, even if they don't have their preferred kind of chocolate.

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Image by Olivia Oliver Design via Unsplash

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Some things happened that we didn't expect...

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Some things happened that we didn't expect...

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If you've been doing the sums as you've been going along you'll have noticed that after chocolate we had 371 participants whereas before we gave out chocolate we only have 358!

Our participants used stickers to give their answers, and we counted these stickers for our results. So where did the extra stickers come from? And how might they affect our results? Let us know what you think in the comments.

More people preferred milk chocolate than white. Do you think this could have had an effect on the results?

What do you think of randomisation? How can this make the trial fairer? Is there anything else we could have done to make it fairer?