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Research topic about how challenging for adults to learn a second language.

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In these ways the review suggests how plasticity, variability and age conspire to frame fundamental research issues in L2 acquisition and bilingualism.

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Department of French and Italian, The University of Texas at Austin, Austin, TX, United States

Much of what is known about the outcome of second language acquisition and bilingualism can be summarized in terms of inter-individual variability, plasticity and age. The present review looks at variability and plasticity with respect to their underlying sources, and at age as a modulating factor in variability and plasticity. In this context we consider critical period effects vs. bilingualism effects, early and late bilingualism, nativelike and non-nativelike L2 attainment, cognitive aging, individual differences in learning, and linguistic dominance in bilingualism. Non-uniformity is an inherent characteristic of both early and late bilingualism. This review shows how plasticity and age connect with biological and experiential sources of variability, and underscores the value of research that reveals and explains variability. In these ways the review suggests how plasticity, variability and age conspire to frame fundamental research issues in L2 acquisition and bilingualism, and provides points of reference for discussion of the present Frontiers in Psychology Research Topic.

Introduction

This review article examines a range of features of second-language (L2) acquisition and bilingualism from the intersecting perspectives of plasticity, variability and age. In the simplest terms, for the L2 context plasticity is a property of the neuro-cognitive mechanisms, structures and systems that enable and constrain L2 learning. Variability in L2 attainment at the individual level is conditioned by factors that may be experiential, biological, intellectual, linguistic, conative, educational, and identificational in nature.

Both variability and plasticity are modulated by the age when L2 learning begins [Age of Acquisition (AoA); see below]. Both main and interactive AoA effects on plasticity have been attributed to neurological maturation, to neurochemical and hormonal fluctuations, to decrements of cognitive function over time, to decreases in regional brain volume, to the degree of first- language (L1) entrenchment at the initial state of L2 acquisition, and to the relative use and maintenance of the L1 vs. the L2 (e.g., Birdsong, 2006; Muñoz and Singleton, 2011). AoA may also indirectly condition learner variables such as the extent to which an individual is motivated to acquire an L2 to high levels of proficiency, to engage in the L2 culture, and to identify with L2 speakers (e.g., Dörnyei and Skehan, 2003; Moyer, 2014).

A comprehensive synthesis of relevant research is beyond the scope of this article. Rather, by use of selected examples, the goal is to expose the essential nature of L2 acquisition and bilingualism from the perspectives of age, plasticity and variability. From these perspectives, we can conceive of linguistic attainment in terms of factors that make L2 learners and bilinguals different from monolinguals, and perhaps get a sense of why these differences are not necessarily deficiencies.

After a brief orientation to the developmental neurobiology of age and plasticity in language learning, I consider the evidence for critical periods in L2 acquisition, taking into account the shape of the function that relates AoA to attainment and the (im)probability of nativelike attainment. The next section offers two illustrations of sources of variation in learning outcomes, which include not only AoA, but also the particular linguistic features under investigation and individuals' cognitive styles and capacities. In the next section I examine possible sources of greater heterogeneity of attainment of L2 morphosyntax with increasing AoA. This is followed by consideration of inter-individual differences, first with respect to exceptional L2 learners and polyglots, then in terms of neurogenetically based talent and trainability, then as a function of idiosyncratic construction of categories for representing linguistic form. In the final section I look at several ways in which linguistic dominance instantiates concerns about plasticity and age, and at how the dominance factor can account for variability in pronunciation and language learning among individual bilinguals.

The works reviewed here converge on the conclusion that studying non-uniformity in language learning outcomes is not so much about sifting through noise and scatter in the data, as it is about illuminating an inherent characteristic of both early and late language acquisition. To this end, it is important to show how plasticity and age connect with biological and experiential sources of variability, and to orient research questions in ways that expose and exploit variability.

A basic motivation of this review is to provide points of reference and theoretical and empirical foundations for readers of the other contributions to the present Frontiers in Psychology Research Topic. In so doing I hope to give a sense of how plasticity, variability and age conspire to frame fundamental research issues in L2 acquisition and bilingualism.

Notes on Terminology and Concepts

In this review, the relationship between age and L2 attainment will be considered with respect to the time at which learning of the L2 begins, be it from birth or at any time thereafter. The term AoA refers to the age at which L2 learning begins in earnest and continues with little or no interruption, most often in immersion contexts such as immigration, but not to limited acquaintance with the L2 that takes place in on trips or in the foreign-language classroom. Note that some studies use the terms Age of Exposure, Age of Immersion or Age of Arrival.

The point at which L2 learning begins is conceptualized as the initial state of L2 acquisition: the sum of an individual's cognitive, neurological, and linguistic development, along with motivational, identificational, attitudinal and experiential characteristics. Since this cluster of features is difficult to quantify, AoA is taken to be a proxy for the L2 acquisition initial state. In this sense, L2 AoA is understood not as the "age factor" but rather as a "meta-variable" ( Flege, 1999). As a predictor variable in statistical analyses, AoA can be applied to both bilingual (simultaneous or sequential) development in childhood, and to immersion and immigration contexts later in life.

In this review, bilingualism is understood to mean routine use of two languages, at whatever level of proficiency in either language. Bilinguals who are immigrants or migrant workers may have acquired their two languages naturalistically only, or they may have had some classroom experience followed by immersion and frequent use. Over the past decade, a disciplinary "bilingual turn" ( Ortega, 2009; May, 2014) in language studies recognizes that "L2 learners" and "bilinguals" are not always distinct populations. Obviously, this conflation does not apply to training studies where, for example, participants are taught an artificial language, Mandarin tone contrasts, or the /r/-/l/ distinction in English. Nevertheless, AoA is commonly employed as a predictive factor for learning outcomes in training studies.

In this contribution critical period is intended as a generic term that subsumes sensitive period. The latter term is sometimes used in contexts of relatively mild maturational effects; at other times it is only meant to suggest heightened receptivity (sensitivity) to relevant environmental stimuli. Both terms refer to finite developmental spans, which may range from birth up to adulthood. In some studies, critical period is taken to mean just the peak period of plasticity or receptiveness of the learning system; in other studies (including the present one), the critical period begins when plasticity starts to increase above baseline and continues until plasticity has leveled out. Maturational effects are thought to take place within, but not beyond, the critical period. For this reason one distinguishes maturational effects from general age effects over the lifespan and, similarly, from AoA effects. For a synopsis of the literature on critical periods for language and other domains, see Birdsong (2017).

Finally, for the purposes of this paper, learning and acquisition will be used interchangeably. (In some studies, the former term is reserved for formal instructional contexts.)

Plasticity, Variability and Age: Developmental Neurobiology and Behavioral Outcomes

The notion of plasticity with respect to adult language acquisition is often traced back to Penfield and Roberts (1959, p. 240), who argue that for recovery from aphasia the adult brain is "inferior" while the child brain is "plastic," that is, more likely to regain language function. Also seminal in this regard are passing remarks by Lenneberg (1967, p. 176), who links L2 learning difficulties in adulthood with hemispheric functional specialization and declines in plasticity that constrain primary language acquisition.

More recent researchers have put forth other neurobiological explanations for plasticity deficits over age. For example, on a "use it then lose" it model, after adolescence the circuitry that is required for language learning is dismantled because in adulthood there remains no selection pressure on humans to keep learning languages and the metabolically greedy neural systems that subserve language learning ( Hurford, 1991; Pinker, 1994). Another proposed neurobiological culprit is maturationally regulated myelination in the circuitry that underlies language learning. On this view, myelination insulates axons for efficient transmission of electrical impulses, but does so at the cost of reducing the synaptic plasticity required for new learning ( Long, 1990; Pulvermüller and Schumann, 1994). Declines in nigrostriatal dopamine over age are implicated in decrements of cognitive abilities such as attention, sequencing, and suppression of competing information; these domain-general capacities are put to use in online L2 processing ( Lee, 2004; Wong et al., 2012; see below). The regulation of plasticity takes place within a critical period, "a bounded maturational span during which experiential factors interact with biological mechanisms to determine neurocognitive and behavioral outcomes" ( Birdsong, 2017).

To get a fuller sense of the neurobiology of plasticity, and how it might relate to variability in language learning, it is instructive to connect critical-period research in the L1 context with studies in L2 acquisition and bilingualism. The essential neurobiological and experiential characteristics of early language learning are authoritatively laid out by Werker and Hensch (2015), who describe the cascading sequence of multiple, overlapping periods of plasticity that enable the development of phonetic perception in the native language, starting with discrimination of linguistic sounds in the first few months of infancy through the structuring of word forms and phonological categories as children approach 20 months of age; see Figure 1.

The chronologies of the onset, the duration, and the closure of each of the critical periods are not fixed, but are manipulated by biological and experiential factors. For example, the timing of the closure of critical periods depends on molecular brakes such as myelin and histone deacetylases, and onset timing can be delayed by sensory deprivation and maternal depression. Thus it is understood that variability and plasticity go hand in hand, as variability within and across overlapping periods of plasticity is a basic feature of the model.

Notably, at the level of the individual child the duration of critical periods in speech perception development can be varied through bilingual experience. As examples, Werker and Hensch cite studies showing that the duration of the critical period for perceptual narrowing - the process by which infants orient their emergent speech perception abilities around just those sounds that occur in their linguistic environment - is longer among simultaneous bilingual children than among monolingual children. The researchers point to several possibilities for this extension.

Relative to monolingual infants, among bilingual infants: native speech categories take longer to establish ( Bosch and Sebastián-Gallés, 2003); sensitivities to speech sounds are maintained until an older age ( Petitto et al., 2012); there is less input per language, with an asymmetric relative frequency of phones within and across the dual-language input ( Bosch and Sebastián-Gallés, 2003); there is enhanced executive control and attentional function afforded by bilingualism ( Kovács and Mehler, 2009); the neural circuitry supporting phonetic discrimination is less mature ( Garcia-Sierra et al., 2011); the circuitry is equally mature but involves a different distribution of neural connections, with greater connectivity in prefrontal areas ( Petitto et al., 2012).

At early developmental stages, the two languages of bilingual infants may resemble those of monolingual children. For example, Burns et al. (2007) found that, at 10-12 months, phonetic discrimination in both languages of English-French bilingual infants of resembled that of monolingual infants and lasted for several months thereafter. Once simultaneous and early bilinguals reach adulthood, however, their processing and production of speech differs from that of monolinguals in each language (see below). More to the point, among adult simultaneous and early bilinguals, variability in speech perception and production is widely attested, and the extent of differences among individuals is in general greater than that observed among native (monolingual) speakers; see Sebastián-Galles and Díaz (2012) for a review. This variability (which may reflect asymmetric exposure to or use of the two languages, or exposure to accented speech in one or both languages, along with motivation, context of learning, inter- individual neurobiological and neurocognitive differences over development, etc.; see further discussion below) is often demonstrated in behavioral studies through comparisons of early or simultaneous bilinguals with monolingual controls at local levels of analysis. For example, Mack (1989) looks at early English-French and French-English bilingual adults, all of whom were English dominant. For /ta/-/da/ discrimination and /i/-/I/ production, the bilingual group resembles English monolingual adult controls. In a separate analysis, however, for the percentage of /i/ vowels whose F2 fell at least 50 Hz between the vowel midpoint and offset, bilinguals differ significantly from monolinguals. Similarly, in Sundara et al.'s (2006) study of /d/-/t/ production, English-French simultaneous bilinguals resemble French monolinguals and English monolinguals for /d/ and /t/ in French and for /t/ in English, but diverge for English /d/.

Plasticity, Variability and Critical Periods in L2 Acquisition

It is commonly believed that L2 attainment to nativelike levels among adults is impossible because they have passed a critical period for successful learning. Two general types of evidence are summoned to support this view. The first is the nature of the function that relates AoA to ultimate attainment. The second is evidence for comprehensive nativelike attainment across all aspects of knowledge, production, and processing of the L2.

The AoA-L2 Attainment Function

Theories of the geometry of the function that relates AoA to ultimate (asymptotic) L2 attainment are reviewed in Birdsong (2005) and Birdsong and Vanhove (2016). In brief, it is thought that departures from linearity in the function would suggest the effects of developmental events leading to qualitative changes in the neurocognitive mechanisms believed responsible for language learning (see Hakuta et al., 2003, for an overview). If instead the function is linear (Figure 2A), this would suggest other types of age-related effects. Some researchers have argued that declines in ultimate L2 attainment should level off after the end of maturation. That is, AoA effects on L2 attainment should be observed among early L2 learners, but AoA should no longer be predictive of L2 asymptote among post-adolescent learners, since maturation would presumably have ceased by this time. On this notion, the geometry of the function should resemble a "stretched L," as seen in Figure 2B. On another view, L2 learning is successful up to a certain age (which may vary depending on what language features are being investigated), and learning ability (and, consequently, ultimate attainment) should decline thereafter. The corresponding shape of the function resembles a "stretched 7," as shown in Figure 2C. A third geometry is that of a "stretched Z," shown in Figure 2D, which combines the "L" and "7" features to include an early plateau, followed by a decline and floor.

FIGURE 2. Schematic representations of age of acquisition (AoA) effects on L2 attainment. (A) linear decline of L2 attainment over all AoA; (B) initial decline of L2 attainment followed by leveling off over subsequent AoA; (C) L2 attainment plateau, followed by decline, followed by leveling off over subsequent AoA; (D) L2 attainment plateau followed by decline over subsequent AoA.

To clarify, note that these are schematic representations only. Depending on methodological considerations (e.g., analysis over the AoA span vs. disaggregation by early and late AoA; choice of regression model, line fitting and smoothing methods, etc.) the observed shapes may have less angular features, and the slopes may be shallower. Also, the timing of the points along the AoA continuum where changes in slope are said to occur varies considerably from study to study. (For further discussion, see Birdsong, 2005; Meulman et al., 2015.)

Another challenge involves the analytical methods that are employed to generate the AoA- attainment function. Different statistical methods applied to the same data may result in different shapes of the function, thus introducing an additional dimension of variability in our conceptualization of plasticity. For example, in Johnson and Newport's (1989) study of Chinese and Korean learners of L2 English, grammaticality judgment scores on a test of English morphosyntax declined linearly over AoA for learners with AoA ≤ 15 years ( r = -0.87, p < 0.01). By contrast, for the later arrivals the scores were distributed more or less randomly ( r = -0.16, ns), and the best-fitting line through the scatterplot of later-arrivals' scores was roughly horizontal. (Note that this unsystematic dispersion was interpreted by Johnson and Newport as a flattening of the AoA-L2 attainment function; see below). In a subsequent reanalysis of the Johnson and Newport (1989) data, Elman et al. (1996) demonstrated that a single non-linear function accounts for about 63% of the variance over all participants' scores, whereas separate linear regressions for younger and older arrivals account for only about 39% of the variance. Importantly, Elman et al. (1996) point out that the overall best-fitting curve produced by the non-linear model is visually a straight line, i.e., one with no apparent inflection or post-maturational leveling-off.

In a re-examination of the Johnson and Newport (1989) L2 grammaticality judgment data, Vanhove (2013) exposes problems with comparing the correlations for early- vs. late-arriving learners in order to infer maturational effects from different correlational slopes. For Johnson and Newport's early arrivals, the slope of the correlation suggested a decline of scores over AoA, whereas for late arrivals the slope leveled off, with no subsequent AoA-related decline in performance. Together the two correlation slopes resembled a stretched "L" corresponding to one proposed version of a critical period for L2 acquisition. However, as noted above, the apparent "flattened" slope (as indicated by a roughly horizontal regression line) is the reflection of the high degree of variability in the performance of the late-arriving learners.

In contrast, using various regression models, some studies find a "stretched-7" geometry for the AoA-L2 attainment function. For example, Hartshorne et al. (in press) elicited grammaticality judgments for English from 669,498 respondents to an online survey, two-thirds of whom were learners of English from different native languages. The results reveal an L2 ultimate attainment plateau that extends from birth to AoA = 10-12 years, followed by an unbounded decline in judgment accuracy over the remaining AoA range. In a masked priming paradigm involving 94 Turkish-English bilinguals who had learned German at various ages, Veríssimo et al. (2017) observe nativelike priming for inflected German participle forms when the participants' learning began before 5 years of age. After this plateau, facilitation declines with increasing AoA, with no leveling off. Another "stretched-7" geometry is noted by Birdsong and Molis (2001) in their replication study of Johnson and Newport (1989). For 61 native Spanish learners of L2 English, an ultimate attainment plateau terminates at a best-fitting inflection point at AoA = 27.5 years, and performance declines thereafter as AoA increases.

Meulman et al. (2015) illustrate the connectedness of analytical choices, the shape of the AoA-attainment function, and variability across structures under investigation. The researchers looked at ERP P600 signatures for the processing of violations of non-finite verbs and grammatical gender agreement in German by Slavic L1 speakers with advanced proficiency in German L2. AoA effects were not found for non-finite verb violations, which are similar in Slavic and German. However, among participants with AoA ≤ 20 years, gender violations elicited a P600, while among those with later AoA a posterior negativity was found in the same time window. Under Generalized Additive Modeling (GAM), and using both AoA and ERP time windows as continuous variables, linear AoA effects on EEG signals were observed across the AoA span, with no discontinuity in the function. Contrarily, ANOVA suggested a critical period prior to AoA = 17.

Non-nativelike Attainment

This argument is implausible, however, because the nature of bilingualism is such that the languages of an active bilingual are activated simultaneously ( Dijkstra and Van Heuven, 2002; Schwartz and Kroll, 2006) and influence each other reciprocally ( Grosjean, 1989; Cook, 1999, 2003; Flege et al., 2003). Given coactivation and bidirectional effects, neither the first nor the second language of bilinguals can be expected to resemble under scrutiny that of monolinguals in either language. Since "two monolinguals in one person" is an impossibility ( Grosjean, 1989), it is unreasonable to hold up a standard of "across-the-board monolingual nativelikeness" in the L2 as a criterion for falsifying the CPH/L2A ( Birdsong and Gertken, 2013).

Attested non-nativelikeness in both languages of an active bilingual has clear implications for theory. To the extent that an account of L2 acquisition predicts that L2 learners should not attain across-the-board nativelikeness if they have passed a biologically regulated critical period, it should also logically predict that the L1 of a bilingual, which is learned within that critical period, should exemplify monolingual-likeness across the board. However, this prediction is not borne out in the relevant research. By contrast, the evidence of bilingualism effects supports an account under which neither the L2 (irrespective of AoA) nor the L1 are completely monolingual-like. Note in this regard that the accuracy figures for bilinguals from birth are significantly lower than those of native monolingual controls in Hartshorne et al. (in press).

These observations connect straightforwardly to questions of age, plasticity, and variability. In their meta-analysis, Liu and Cao (2016) cite studies of L1 permeability in bilingualism, which reveal different patterns of neural activation in the L1 after vs. before acquisition of the L2. Introducing the AoA factor, several reviewed studies converge on the finding that early bilinguals, relative to late bilinguals - with both sampled populations having the same L1 - showed greater activation in the left fusiform gyrus than late bilinguals when processing the L1. This result suggests that the effects of the L2 on L1 processing in imaging studies may be more pronounced with earlier AoA of the L2, as the L2 'interferes' more with the L1 to the extent that development of the two languages overlaps temporally. This relationship is attested as well in behavioral studies.

The basic notion that L2 ultimate attainment is conditioned by the age of initial immersion or significant exposure is examined by Qureshi (2016) in a meta-analysis of 26 studies of morphosyntactic knowledge. The materials reviewed largely substantiated the general idea of AoA effects (as opposed to maturational effects, which were not explicitly examined). At the same time, experiential and methodological factors were found to introduce considerable variability in outcomes. For example, in studies of classroom learning of a foreign language, there was no evidence of an "early advantage" (see also Huang, 2016), whereas the "early-is-better" rule of thumb was supported in studies of immersion learners.

Nativelikeness

It is important to emphasize that, despite bilingualism effects, there are late L2 learners who resemble native monolinguals with respect to targeted aspects of the L2 (as opposed to bilinguals being indistinguishable from monolinguals in every measurable respect). Behavioral evidence ranges from acquisition of fine-grained phonetic features such as VOT to global pronunciation ( Bongaerts, 1999; Flege et al., 2002; Birdsong, 2007; Moyer, 2014) and from surface morphology to abstract features of syntax ( Birdsong, 1992; Birdsong and Molis, 2001; Donaldson, 2011; Destruel and Donaldson, 2017). In online tasks such as self-paced reading, late bilinguals show monolingual-like sensitivity to subtle and unique aspects of the L2 such as order of clitic pronouns ( Rossi et al., 2017). In brain-based studies, high-proficient late L2 learners exhibit convergence with native participants ( Green, 2003) in the processing of information structure ( Reichle and Birdsong, 2014) and across a variety of syntactic and morpho- syntactic features: see Steinhauer (2014) for a review of the electrophysiological literature; see Abutalebi (2008) for a review of the functional neuroimaging literature.

The incidence of nativelikeness among late L2 learners can vary as a function of the particular structural characteristics that are investigated and as a function of the experimental procedures that are employed. For example, in a series of experiments that involved both ERP and eye-tracking methodologies, Foucart and Frenck-Mestre (2012) find that violations of noun-adjective gender agreement in French trigger nativelike P600 signatures among English-speaking late learners of L2 French when the adjectives follow the nouns, but elicit non-nativelike N400s when the adjectives are preposed. When the stimuli involve agreement violations in predicative structures (where the noun and the adjective are separated by a copula), natives and learners diverge in terms of ERP, but show similar patterns in eye tracking.

In some of these and related studies, the findings of nativelikeness have been interpreted as counter-evidence to critical-period predictions with respect to the attainment of nativelikeness in late L2 acquisition articulated. Recall, however, that proponents of the critical period hypothesis in the L2 context advance the criterion of across-the-board nativelikeness as necessary evidence for rejection of the hypothesis. From this perspective, among late (or early) bilinguals it is not enough to find "pockets" of nativelikeness with respect to grammatical knowledge and online processing, or brain activation patterns that resemble those of monolinguals, or individuals who diverge from controls only on VOT values for /d/ in word-final position, but in no other respect.

Under comprehensive, microscopic scrutiny, even among the most practiced hyper-polyglots (see section "Individual Differences in L2 Learning," below), some scintilla of non-monolingual-likeness can be found among active bilinguals.

As stated above, however, the position regarding falsification of the hypothesis by impeccable nativelikeness does not take into account the natural effects of bilingualism, which make it impossible for both early and late bilinguals to be exactly like monolinguals in either the L1 or the L2. It was also noted that, by the logic of this position, for rejection of the nature-of-bilingualism account (and for support of the critical period account) one would need evidence of across-the-board monolingual-likeness in the first-learned language of late bilinguals, or in either language of simultaneous bilinguals ( Birdsong and Vanhove, 2016).

Sources of Variability in L2 Acquisition

Two Illustrations

FIGURE 3. Results of a test of English morphosyntax, as a function of age of arrival in the United States. (A) Shows overall percent correct for Korean native speakers (filled circles) and native English controls (open circles); (B) breaks out test results by grammatical items (top) and ungrammatical items (bottom); (C) depicts different functions for ungrammatical rule-based items vs. ungrammatical lexically-based items. Adapted from Flege et al. (1999). Republished with permission from Elsevier.

With increasing AoA, the learners' results become more dispersed. Figure 3B plots the L2 English performance on the same items, broken out by those that are grammatical (top image) and ungrammatical (bottom image). Both the top and bottom images reveal increased variability over AoA; however, the degree of variability depends on the grammatical status of the items analyzed, with the cone-shaped scatter of results more pronounced for responses to ungrammatical items than to grammatical items.

Another source of variability is the test items themselves, as shown in Figure 3C. For ungrammatical "rule-based" items that exemplify regular, generalizable features of English surface morphology (e.g., -ed past inflection on verbs; case marking on personal pronouns), the slope of the decline in performance over AoA is relatively shallow. By contrast, a steep decline over AoA is observed for ungrammatical "lexically-based" items that exemplify idiosyncratic features of English, such as prepositions preceding infinitival complements ( ∗let to watch vs. let watch) and noun complements (e.g., ∗hoping rain vs. hoping for rain). Note as well that the shape of the function for the ungrammatical lexical items roughly resembles the schematic "stretched-Z" geometry (see Figure 2C), while the function for the rule-based items is closer to linearity (see Figure 2A).

As a second illustration of sources of variability, Ettlinger et al. (2014) examine the possibility that L2 learner strategies and success vary according to domain-general cognitive skills. In an artificial language based on Shimakonde, a Bantu language of Mozambique, university student participants were trained on noun stems, plurals, diminutives, and diminutive plurals representing animals. For two types of diminutive plurals in the language, the diminutive and the plural morphemes are simply affixed on the singular stem. A third type of diminutive plurals is more complex, as the vowels in the stem and the plural affix require rephonologization. After exposure to word-picture pairs, participants were asked to produce diminutive plurals on novel words à la the wug test ( Berko, 1958). Some learners (termed Simplifiers) tended to apply the simple pattern in instances of both complex and simple diminutive plurals; others (Learners) successfully learned both the complex and simple diminutive plurals; others (Non-learners) performed poorly overall. On a prior test of working memory, Learners, Simplifiers and Non-learners performed similarly. However, the groups varied on prior tests of procedural memory and declarative memory. Those participants who were Learners generally scored high on both procedural and declarative memory tests. Those with high procedural memory scores, but lower declarative memory scores, tended to be Simplifiers. Those with poor procedural memory, irrespective of declarative memory scores, were Non-learners. These results, summarized in Figure 4, suggest a connection between learner types and L2 learning performance: differences in domain-general cognitive capacities account for some inter-individual variation in L2 learning.

Variability in L2 Attainment With Increasing AoA: Possible Sources

In some studies, as AoA increases, the outcome of learning of L2 morphosyntax appears to become more variable (see, e.g., Flege et al., 1999; Vanhove, 2013). Candidate sources for such wide dispersions can be inferred from an increase over age of the range of values that are associated with relevant experiential variables. For example, in a random participant sample, the range of lengths of residence in the L2 environment, along with the range of years and types of education will increase correspondingly with AoA. Along with such scaling effects on demographic variables, it is also possible that, with increasing AoA, motivation to attain accuracy in lexico-grammatical knowledge in L2 will become more heterogeneous across participants, particularly so as goals for L2 learning become more diverse.

Cognitive aging may also figure in the mix of candidate reasons for age-related variability in L2 attainment. For example, Buczylowska and Petermann (2016) summarize age-related differences in six executive function tests administered to 484 participants ranging in age from 18 to 99 years. Declines in mean scores over age were accompanied by increased age-dependent heterogeneity in scores. Connecting this finding to the cone-shaped dispersion of L2 morphosyntax scores over AoA is not a straightforward matter, however, as the heterogeneity observed by Buczylowska and Petermann (2016) is most notable in the later age ranges, whereas most individuals undertaking L2 do not begin so late in life. Further, the degree of dispersion varied greatly by task in this study. Similarly, Mella et al. (2016) show that results on tests of processing speed and working memory do not display the same inter-individual variability with increasing age. Relatedly, Hartshorne and Germine (2015) find that the peaks in cognitive skill are not synchronized over skill types, with some occurring earlier than others. The occurrence of multiple décalages in the timing of peaks (and subsequent declines) suggests that whatever scatter of performance there is over age may not be uniform over intelligence types.

A strong case can be made for both general effects and inter-individual effects of progressive cognitive decline, as well as for effects of dopamine declines (see above), progressive L1 entrenchment ( Marchman, 1993; Elman et al., 1996; Flege, 1999; MacWhinney, 2005), and education ( Bialystok and Hakuta, 1999; Birdsong, 2014b) on L2 attainment over AoA. At the same time, it is fair to say that further study is needed to establish a direct link between heterogeneity in cognitive function over age and AoA-related patterns of dispersion of results on tests of L2 attainment.

Individual Differences in L2 Learning

It is axiomatic that people vary widely in the effectiveness and efficiency with which they learn an L2. Often the study of individual differences in L2 learning focuses on exceptionally successful learners. Although researchers do not all agree on terminological distinctions between the notions of ability, aptitude, talent, and giftedness in the context of L2 learning, the cognitive and conative attributes of high achievers in this domain are well understood; for a recent review, including the question of the mutability of aptitude with experience, see Singleton (2017).

Biedroń and Birdsong (in press) point out that, to the extent that complete monolingual nativelikeness is taken to be criterial, extraordinary polyglots do not constitute so-called "exceptions to the critical period hypothesis" for L2 acquisition. As suggested above, it is more apposite to point out that there are no exceptions to the effects of bilingualism, even among the most talented learners of languages. As Biedroń and Birdsong observe, "the special significance of the impossibility of multiple monolingual-likenesses resides in the fact that, no matter how gifted a multilingual is, s/he can't suppress in an absolute sense the other language(s)."

Turning to less exceptional cases, Della Rosa et al. (2013) proffer a view of individual talent in multilingualism that relates language-learning-induced plasticity in the left inferior parietal (LIPL) region of the brain to enhancement of domain-general attentional processes. Their longitudinal study of children living in the South Tyrol region of Italy, where German, Italian, Ladin and English are routinely used, showed specific multilingualism-induced gray matter volume increases in the LIPL. The researchers suggest that such structural adaptations result from the necessity to apply general memory and attentional functions to the processing of more than one language.

A neurogenetic approach to individual differences in L2 learning is advanced by Wong et al. (2012), who specify the mediating roles of genetically encoded dopaminergic (DA) reception and transmission that underlie the acquisition of procedural aspects of grammar. Procedural learning is associated with concatenation of constituents in syntax and with abstract relations between phonology and morphology, and is localized in the prefrontal cortex and basal ganglia. Given what is known about idiosyncratic variability in DA-related gene function, expression and biochemistry, "it is not surprising that individuals with different genetic profiles may have different learning capabilities" ( Wong et al., 2012, p. 1093), with more variation expected in adult L2 acquisition than in L1 acquisition. These differences extend to inhibitory function and executive control, which in L2 processing enable suppression of competing information such as knowledge and intrusion of the L1 ( Lee, 2004). Under the DA account, a mediating role of AoA can be postulated as well, as dopamine receptor and binding declines over age are well documented (e.g., Volkow et al., 1998; Prull et al., 1999; Bäckman and Farde, 2005).

A dual-systems learning model developed by Chandrasekaran et al. (2014) looks at the use of reflexive vs. reflective learning systems in speech category learning in a training paradigm. The reflective system explicitly develops and tests categorization rules; in contrast, the nature of the reflexive system is procedural and implicit. In experiments involving novel linguistic tone category learning, adult participants initially display a bias toward using the reflective system, which turns out to be ill-adapted to the task. Those individuals who succeed in tone learning are able to shift to the reflexive system, using cortico-striatal connections whose plasticity is regulated by DA reinforcement signals. Relative to younger participants, older adults appear to be less likely to be able to shift from reflective learning to reflexive learning.

Birdsong (2012) examines native-language literacy and education as sources of variability across participants in L2 attainment studies. These factors may interact with task type (e.g., grammaticality judgments vs. truth-value tasks; elicited speech vs. read-alouds), measure (e.g., behavioral vs. brain-based measures; speed vs. accuracy) and linguistic domain (e.g., quantifier scope, garden-path structures). Birdsong (2012) also notes that both native speakers and L2 learners exhibit grammatical idiosyncrasies and other types of variability in representations of linguistic structure ( Dabrowska, 2012); therefore variability per se (whatever the type or source) is not necessarily evidence of learning deficiencies.

According to Birdsong (1994), the ability to make judgments about linguistic form differs across individuals, who vary in the way they construct language-relevant categories such as "well- formed sentence" and "plausible interpretation." Individual learners may also differ in assessments of the typological relatedness of their L1 to their L2, which modulates their decisions about the likelihood that features of their L1 will resemble those of their L2. Birdsong (2009) characterizes individual differences in learners' ability to notice subtle linguistic features of the L2 within the general framework of signal-detection theory.

For an overview of individual variation in L2 processing (as opposed to attainment), see Van Hell and Abdollahi (2017).

Dominance, Plasticity, Variability and Age

A feature of bilingualism that conspicuously connects age, plasticity and variability is linguistic dominance. Regarding plasticity and age, it is not always the case that language learned in infancy is the dominant language of a bilingual: the neural mechanisms involved are sufficiently plastic that the L2 can "leapfrog" the L1 in terms of proficiency and processing ease. Among international adoptees and heritage speakers, dominance shifts involve attrition of the L1, a representational and functional loss which likewise reflects neural plasticity (see below). As concerns variability, inter-individual differences in dominance relationships are natural consequences of idiosyncratic experiences with, skills in, and use of the two languages. No two bilinguals are identical in terms of dominance.

As with many other features of bilingualism, linguistic dominance is not inherently categorical. That is, individual bilinguals are not simply "L1-dominant" or "L2-dominant," they are dominant in one or the other language to varying degrees. Accordingly, in order to faithfully capture the construct, dominance, like AoA, is properly operationalized and analyzed as a continuous subject factor. As with any other continuous variable, participant assignment to dominance categories may mask intra-group variability and result in loss of statistical power (e.g., Altman, 1998). Some instruments for assessing dominance take into account both domains and dimensions of dominance. Birdsong (2016) reviews methods of calculating dominance indices, along with problems of incommensurability in comparing individual bilinguals who may have the same composite dominance indices, but who vary with respect to the underlying dimensions and domains measured by the instrument.

Balanced Bilingualism

So-called "balanced bilinguals" are dominant in neither language. The term is sometimes used or assumed to denote very high or (near-)nativelike proficiency in both languages. However, degree of proficiency is independent from degree of dominance. An individual who is at an equally low proficiency level in two languages, and an individual who is highly and equally proficient in two languages, are both by definition balanced bilinguals. As depicted by Goto Butler and Hakuta (2004), Figure 5 shows that balanced bilinguals fall at any point along the diagonal line of increasing proficiency. Bilinguals who are not balanced (that is, who are dominant in either Language A or Language B) are situated to one side or the other of the diagonal.

The related idea of "perfect bilingualism," if understood as monolingual-likeness in two languages, is misguided since, as noted earlier, neither the L1 nor the L2 of bilinguals is identical to the corresponding languages of monolinguals in all measurable respects. Becoming "more bilingual" is, however, sometimes thought to suggest getting closer to "perfect bilingualism." At the same time "more bilingual" has been taken to mean that a given bilingual is highly proficient in the two languages, or to mean approaching balanced proficiency.

Dominance Shifts and Age

The direction and degree of dominance in the two languages are dynamic over the lifetime of an individual bilingual. Depending on changing circumstances such as immigration, educational and occupational opportunities, and psycho-social identification, the L2 may "replace" the L1 as the dominant language. In some cases, and for similar reasons, the L1 may return to dominance, and still further shifts are possible. Grosjean (2010) details multiple dominance shifts over 60 years of his life. For a review of research and theory on the relationship between dominance and age, see Birdsong (2014a).

Conceptually as well as in practice, the developmental dynamics of dominance relationships may reflect both L1 loss and L2 gains. For example, among some immigrants and adoptees, there may be little or no ongoing use of the L1; as the L1 withers (in terms of domains or dimensions), the L2 perforce becomes the dominant language. On a developmental scenario, a sequential bilingual whose L1 is not fully developed may use and maintain the L1, but as a matter of relative gains in linguistic knowledge and proficiency over time, the L2 eventually outstrips the L1.

Thus, with respect to plasticity in dominance relationships in the first decade of life, there are two distinct possibilities. One possibility is that L1 loss, the likelihood of which is highest for several early years, is a greater contributor to dominance shifts than L2 gains, which start to become less likely very early in life, with progressively less influence on shifts from L1 to L2 dominance. Another possibility is that L2 gains and L1 losses conspire simultaneously to enable L1-to-L2 shifts of dominance. The latter possibility relates L1 loss and L2 gain under a unified view of plasticity in early childhood development: "the ease with which an L2 is acquired and the L1 undergoes attrition can be said to be manifestations of a generally heightened responsiveness to language exposure, which works both in acquisitional and attritional directions" ( Bylund et al., 2012, p. 237). For a recent empirical study and review of age effects on L1 attrition, see Ahn et al. (2017).

Note that age conditions not only the probability of L1 loss, but also the speed at which attrition occurs ( Köpke and Schmid, 2004). As L1 loss slows, the point at which a complete shift to L2 dominance can be expected is delayed. Similarly, depth of attrition (the degree to which a domain or dimension is diminished) and breadth of attrition (the number of dimensions and domains diminished) should decrease with the age at which the loss begins. Thus, indirectly through L1 loss, age contributes to variability in L1-L2 dominance relationships (see also Montrul, 2016b).

Examples of Prediction and Variation in Dominance

A critical take-away from Baird (2015) is that the nature of inter-individual variation is obscured in a simple analysis by binary factors, in this instance place of residence and pre- vs. post-stress F0 peaks. More revealing can be examinations of variation along continuous dimensions, in this case distance of peaks from the tonic syllable and degree of Spanish vs. K'ichée dominance. By such an analysis, individual variability along a continuum of peak F0 placement is predicted by degree of dominance, independently of residence.

As a related and final example, recent work by Onnis et al. (2018) looks at dominance as a predictor of statistical learning among adult bilinguals in a miniature grammar paradigm. (Statistical language learning involves tracking the frequencies of, or the transitional probabilities between, grammatical elements, which results in implicit knowledge of structural regularities.) In this study, success in statistical learning of artificial grammars is predicted by the degree to which participants approach or depart from balanced bilingualism, as measured by BLP scores: balanced bilinguals perform better than those who are increasingly dominant in their first language. Thus, degree of bilingual dominance in adulthood is associated with differential ability to learn a novel language. Onnis et al. (2018, p. 432) summarize their findings: "By capitalizing on the bilingual variability we found in the [BLP] questionnaire rather than ignoring it, we unearthed important individual differences that point to the first documented modulating role of [degree of dominance in] bilingualism in adult statistical learning."

Conclusion

In this review we have seen how variation in L2 acquisition and bilingualism is conditioned by age, which itself conditions plasticity. We also know that age similarly conditions individual factors such as language experience, L1 attrition and linguistic dominance, which are themselves predictive of variation.

Age-related effects (of which neurobiological maturation within a critical period is one possible source) cannot account for all varieties of non-nativelike outcomes in L2 acquisition, since departures from monolingual-likeness are found not just in post-childhood learning but among from-birth simultaneous bilinguals as well. By contrast, bilingualism effects can account for observed non-monolingual-likeness in both the L1 and the L2, whatever the age of learning. At the same time, the degree of L1 activation, L1 entrenchment, L1 attrition and relative L1-L2 dominance - all of which are affected by AoA - modulate attainment levels across L2 learners.

The application of different statistical models and methods can result in different shapes of the function that relates AoA to L2 outcomes; such artifacts add another dimension of variability to the picture of L2 acquisition. We have also considered possible sources of variability in L2 attainment with increasing AoA. These sources range from experiential (education, length of residence), to representational (L1 entrenchment) and to cognitive decline with underlying neurologic causes such as dopamine levels that mediate domain-general learning and processing. The role of cognitive decline in AoA-related variability in L2 learning outcomes is of particular interest for future investigation.

This review has brought these concerns into focus with illustrations from two areas of active research, individual differences and bilingual dominance. With respect to individual differences in L2 learning, we have highlighted the roles of neurogenetic makeup, higher-order cognitive factors, language experience, age-conditioned learning styles and motivation. We have seen that the gradient phenomenon of dominance in bilingualism is dynamic over the lifespan, is conditioned by experience as well as by neural plasticity, and is predictive of phonetic variation, cognitive control, and statistical learning in artificial language paradigms.

In his classic position paper Bley-Vroman (1990, p. 13) problematizes adult L2 learning in terms of explaining "the quite high level of competence that is clearly possible in some cases, while also permitting the wide range of variation that is observed." By demonstrating the connectedness of non-uniform outcomes with age and plasticity, the research reviewed here has shown that such variation is neither unexplainable nor unexpected. From this understanding emerges heuristic guidance for further explorations of the richness of L2 acquisition and bilingualism.

Author Contributions

The author confirms being the sole contributor of this work and approved it for publication.

Conflict of Interest Statement

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

Bäckman, L., and Farde, L. (2005). "The role of dopamine systems in cognitive aging," in Cognitive Neuroscience of Aging: Linking Cognitive and Cerebral Aging, eds R. Cabeza, L. Nyberg, and D. Park (New York, NY: Oxford University Press), 58-84.

Biedroń, A., and Birdsong, D. (in press). "Highly proficient and gifted bilinguals," in Handbook of Bilingualism, eds L. Ortega and A. De Houwer (Cambridge: Cambridge University Press).

Birdsong, D. (2017). "Critical periods," in Oxford Bibliographies in Linguistics, ed. M. Aronoff (New York, NY: Oxford University Press).

Destruel, E., and Donaldson, B. (2017). Second language acquisition of pragmatic inferences: evidence from the French c'est-cleft. Appl. Psycholinguist. 38, 703-732. doi: 10.1017/S014271616000400

CrossRef Full Text | Google Scholar

Hartshorne, J. K., Tenenbaum, J. B., and Pinker, S. (in press). A critical period for second language acquisition: evidence from 2/3 million English speakers. Cognition.

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Plasticity, Variability and Age in Second Language Acquisition and Bilingualism

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Much of what is known about the outcome of second language acquisition and bilingualism can be summarized in terms of inter-individual variability, plasticity and age. The present review looks at variability and plasticity with respect to their underlying sources, and at age as a modulating factor in variability and plasticity.

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Sanz Cristina
"Mind And Context In Adult Second Language Acquisition"

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From the video it shows that children learn language easier than adults because adults cannot acquire a new language as easily as a child.

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**lin⋅guis⋅tics**: the scientific study of human *language* * what form does it take? * how is meaning constructed? * how is it structured? * how is it produced?

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r/linguistics - Why Can't Adults Learn Languages Like Children?

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New comments cannot be posted and votes cannot be cast View entire discussion (107 comments) **lin⋅guis⋅tics**: the scientific study of human *language* * what form does it take? * how is meaning constructed? * how is it structured? * how is it produced?

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I did an interview with Mr. Musa, he is 52 years old adult. Graduate pursuing a doctorate degree, which he is doing perfectly well because of his determination, plan, allocation, time, and resources and more especially the advancing technology. He disagrees that adults can learn more than children nowadays. As an adult, he can learn new language easily because of the following reasons. If he decides to learn a new language, he must have a strong reason for doing so, with the motivation factor in his mind he will allocate time and resources to do so.
As an adult, he uses technology like phone, iPad and tablet to benefit him more than children and young person do. There, he will use the latest skills in the system to easily learn a new language than engage in a video games. As an adult, he can early learn and retain what he learnt better than kids who keep on changing with the world dynamics.

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Adults famously find language learning more difficult than young children. According to Joan B. she points out "As an adult, on the other hand, learning a new language is definitely a different experience."

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It's never too late to learn a second language! Sure, kids may have those "spongy" brains... but the reality is, there are many advantages to learning a new language as an adult. Here, Spanish tutor Joan B. explains...
If you studied a language in middle school or high school, you might recall the days of memorizing verbs and vocabulary for your exams. Maybe you also recall learning with ease as you familiarized yourself with foreign sounds, words, and experiences.

As an adult, on the other hand, learning a new language is definitely a different experience. It's not all bad, though: there are some big advantages, too! Understanding how adults learn differently will help you stay aware of possible challenges, while taking advantage of the benefits of being an adult learner.

Let's start with the challenges of learning a new language as an adult:
1. You'll need more discipline to make time for lessons and studying.
"Adulting" takes time, and it can be hard to fit in regular lessons and study, both of which are essential for consistent progress in your target language. While you might not have afternoons free like you did as a child and young adult, I recommend blocking out times in your schedule that are distraction-free and one hundred percent focused on language learning. Even if the chunks of time are short, consistent study will lead to noticeable progress, so keep it up!
2. Losing your American accent completely can be difficult.
When children learn a new language, they naturally assimilate the unique sounds, inflection, and rhythm of the language. As adults, it can be harder to completely master the accent, as the foreign sounds can be challenging to assimilate completely since speech patterns are already set.

There's good news, though: if you were exposed to the sounds of foreign languages as a child, that can be enough to make learning a new accent easier, as studies have shown that just exposure as children, even without speaking, can familiarize us with the sounds at a later date.
3. You might not have the time for a thrice-weekly or daily class like you had in middle or high school.
And even without that exposure, there are many ways your tutor can help you improve your accent if it doesn't come naturally to you. Working with a language tutor - as opposed to relying on prerecorded courses, videos, and apps - is key, as you'll get feedback and corrections as you're speaking.

You may have counted down the minutes until the end of the school day, whereas now you dream of uninterrupted time for study and self-development as a working adult. The upside is that there are many opportunities for adults to pursue intensive, serious study, as well. You might even benefit more as a serious adult student than you did as an adolescent.
4. Spontaneity is often tempered by fear of making mistakes.
Examples of study you could undertake include summer or winter intensives during time off of work, night classes, online group classes, and private tutoring sessions, all of which can fit into the busiest of schedules. With these ideas, you'll be learning your target language in leaps and bounds!
5. Vocabulary acquisition needs targeted practice.
A big difference between adults and kids is that the latter group is often unhampered to try new things, even if it means looking a little ridiculous and making errors. Adults can be intimated by trying new things, and making errors is frowned upon.

This can make it challenging to learn well, as an inherent part of language learning is to make mistakes and experiment! You can remain aware of this downfall and work to overcome fear of mistakes by staying open, having fun, and trying new things.

As an adult, it's often not enough to just rely on exposure to acquire and memorize new vocabulary. As you learn, you'll need to make a targeted and concerted effort to memorize new vocabulary. Children and adolescents can often pick up new vocabulary simply through exposure and repetition; the advantage adults have is that they can choose to focus on specific vocabulary sets that interest them. These could be highly specific (i.e. Spanish vocabulary for healthcare) or general; either way, you'll be learning exactly what you want to learn, which should feel good!
1. Adults posses greater comprehension ability and organizational practices.
Children learning new languages often pick up sentence structure and other grammatical points simply by listening and interacting. Adults, on the other hand, may struggle with structures that are different in their native language. Because of this, grammatical exercises and dedicated study are usually necessary.

However, adults can use the grammar rules they already know and understand as a jumping off point for learning a new language's grammar. This can be advantageous as well as an interesting exploration if you have an interest in how languages function. To sum it up, adults can often explain the "why" behind a usage in a language, while children can only execute the grammatical function without the capacity to explain.
2. As an adult, you're choosing to study language.
We've alluded to a few of the advantages already, but did you know there are more? The next time you're worried it's too late to learn a second language, keep these four things in mind.

Many parents choose to raise their child bilingual, since young brains can rapidly absorb new information. However, as an adult you will be empowered by your ability to organize, summarize, and comprehend things on a macro-level. Translation: you can see the smaller details within a language, as well as the bigger points you need to master to speak well.
3. You'll pick up cultural nuances easier.
This ability allows you to progress rapidly in a language - if you're dedicated, consistent, and motivated. You may never be able to learn totally through exposure like a child, but with the above skills, you'll find yourself speaking and understanding your target language in no time.

As a high school student, you may have studied a language simply to fulfill a requirement - not the greatest motivator to fuel language acquisition. As an adult, you've chosen to study a second language based on your interests, goals, and motivations. Perhaps you want to travel and communicate with locals, use it in your work, or communicate with a loved one, romantic or otherwise.
4. You have more opportunities for practicing your target language.
Here's your advantage: you can use this motivation to engage more deeply with the language, and simultaneously improve more rapidly. It's the opposite of learning something only to replicate the information on a written exam to pass a class. Bonus: discuss your goals with your teacher or tutor so he or she can tailor your lessons to your interests!

The subtleties and finer points of a language may (or may not) be unconsciously absorbed by children; however, adults can consciously notice these elements and use that information to enhance their understanding.

This can allow you to assimilate more easily into the foreign culture of the language you're learning, plus pick up on nonverbal and social cues. You'll appear more confident and informed when you find yourself interacting with locals while traveling or just in everyday life.

As a younger student, your opportunities for practicing a language were probably restricted to the classroom setting. As an adult, the world is your oyster! You can practice during Skype calls with friends learning the same language, explore a neighborhood in your city that will give you more exposure, or even travel internationally.

Just remember to strike a balance; it's important to study formally with language materials, but immersion learning will help you master the art of conversation and local dialects.
Photo credits: The LEAF Project, x1klima
Ready to Get Started?

As you can see, learning a new language as an adult can be quite different from how you learned as a child! Hopefully you can also see the myriad challenges and advantages, and use them to learn intelligently and enjoyably as you gain fluency in your target language.

Perhaps the most important thing to remember is that each language learner is different; regardless of age or prior language-learning experience, everybody learns in a unique way. Think about your learning style and goals, and let your tutor know. Enjoy your journey!

Post Author: Joan B.
Joan B. lives in Carmichael, CA and has been teaching high school Spanish for more than 18 years. A lover of language, she's studied French, Arabic, and Italian and spent time living in Spain. Learn more about Joan here!

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6 Challenges & 4 Advantages Adults Have Learning Languages

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It's never too late to learn a second language! Sure, kids may have those "spongy" brains... but the reality is, there are many advantages to learning a new language as an adult. Here, Spanish tutor Joan B. explains...

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Show that children are more capable of acquiring another language more quickly and simply than adults, they can easily absorb language faster because theirs brains are almost twice as active. Joshua K. Hartshorne, Joshua B. Tenenbaum, and Steven Pinker, explain "Children learn language more easily than adults"

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This article examines the advantage for adults to learn second language.
"The difficulties associated with language learning in adulthood and demonstrates that some of an adult’s innate weaknesses might actually be an advantage."

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Those of us with children willhave noticed how quickly they make progress in language acquisition. Within the short space of time, a child can go from babbling to forming coherent sentences. This is all the more amazing since they do this through simple exposure to the language, without any formal instruction. Any adult learner hoping to match this progress will have to spend long periods of time at study, memorizing vocabulary and conjugations.

Why is language learning in adulthood different to language learning in childhood?

Young children progress so quickly because of their neuroplasticity. At their stage of development, they absorb new information much more readily than adults. New information can more easily become part of their procedural memory, allowing them to learn to perform tasks automatically, without any conscious effort. Many scholars assume that once children reach a certain age, their ability to learn a new language begins to decline. Beyond adolescence, we must make specific, conscious efforts to acquire new skills. We will not make progress without many hours of practice.

This article examines the difficulties associated with language learning in adulthood and demonstrates that some of an adult's innate weaknesses might actually be an advantage.

The critical period hypothesis

The critical period hypothesis proposes that if a child does not learn a language by a certain age, then they will never adequately learn one.

Researchers have described examples of so-called ' feral ' children, whose circumstances meant that they did not receive sufficient exposure to a language in their earliest years. Many of these children struggle to communicate throughout their entire lives, even after receiving significant remedial intervention. Some of them never adequately acquire a language.

Studies have also applied the critical period hypothesis to second language acquisition. Although it is not universally accepted, researchers have observed that younger learners acquire a second language relatively easily in comparison to adults, who may never achieve full fluency.

Phonology

The sound system of a language appears particularly susceptible to the constraints of the critical period. There are many adult second language learners who demonstrate mastery of the grammar of the target language, but retain patterns of pronunciation which are comparable to those of their native language.

Second language acquisition in adulthood - what is the goal?

Language learning never ends. A learner will never reach a point at which they can state that they have complete knowledge of a language. Languages constantly evolve. New words emerge every day and even native speakers struggle to stay on top of the changes to their language. An adult learner should not be discouraged by the fact that they are unlikely to be able to emulate the speech of native speakers entirely. Absolute mastery of a language in all areas is an almost impossible task, even for native speakers.

Why aim to learn a language in adulthood if we will never be able to master it completely?

Near-native mastery of a language is not a practical goal for someone who is just beginning to learn the language. A learner would very quickly lose motivation once the enormity of such a task becomes apparent. Learners should set smaller, more achievable goals in the earlier stages. Near-native command of the language might be achievable in the long term, but there are plenty of more meaningful goals which can be achieved in the short to medium term.

Should an adult learner aim to emulate a native speaker?

The merits of learning a language to a near-native standard may seem obvious. However, it is important to consider if it is worthwhile, or even desirable, to emulate a native speaker. If you live in an area where another language is widely spoken, then it might be necessary to speak to a near-native level. However, it is possible that the learner is not aware of which variety of language they are emulating.

All languages have social and geographical variation. This variation is most pronounced in phonology, the domain most sensitive to the apparent prescriptions of the critical period. A learner is likely to imitate the pronunciation of the variety to which they are most exposed, perhaps unaware that certain forms have an association with a particular region or a particular group of people. Using such forms can potentially cause difficulties for learners. It might be advantageous for an adult learner to maintain their status as a non-native in order to avoid misunderstandings.

Potential difficulties of choosing one variety over another

To cite a personal example, I once spent a summer working as a camp counselor in Italy. I worked with teenagers for the summer and their speech formed the basis of my exposure to the Italian language. By the end of my stay, I spoke the language quite fluently, thanks to my near total immersion.

However, the variety of language which I was emulating was not a prestigious variety. Forms that are in common use among teenagers are not necessarily acceptable in polite conversation. I later found out, to my embarrassment, that I was swearing more than was normal. My usage of the language was too informal - I did not have adequate tools to interact within more formal environments. While I had worked hard to reproduce the language of my surroundings, it was only later that I realized the stigma of some of the forms I had acquired.

The neutrality of the non-native

The sound system of the target language presents the greatest challenge for adult learners. However a non-native accent might be more desirable because of its inherent neutrality. A learner who aims to emulate a native variety may unwittingly use forms which have implicit social or political connotations. A learner who makes use of these forms risks alienating themselves from certain sections of the native speaking community. A non-native variety, as long as it can be understood, should be free of these connotations. Furthermore, speaking with a non-native accent allows a learner to assert their own identity. As long as the speaker's accent is understandable, then there is no reason to aim to emulate a native speaker perfectly. As we have seen, retaining traces of your native variety can be advantageous.

Hard work pays off

Forming strong study habits is integral to success in adult learning, whether learning a language or a martial art. Anyone who takes the time to learn will inevitably make progress. Isn't this comparable to the miracle of childhood learning? That hard work will inevitably yield rewards? Where children have a natural propensity for learning, adults have a natural propensity for organization. An adult learner should aim to harness these innate skills by setting goals. For example an adult who uses an app like Clozemaster every day for six months will make enormous strides in their learning, perhaps without realizing.

A child can never use its innate learning power to its full potential. They do not understand their capabilities until it is too late. Hard work and organization are the primary gifts which adult learners have at their disposal. The sense of achievement that is unlocked through use of these gifts is more meaningful than anything a child experiences. The wisdom to understand that hard work pays off is an advantage that only an adult learner can appreciate.

Conclusion

Although it is difficult to prove, it seems clear that language learning is an easier task for children than adults. Nonetheless, learners should not be discouraged - language learning in adulthood is possible. With hard work and motivation, adult learners can make tremendous progress within short periods of time. Researchers have ascertained that it is the sound system which appears particularly difficult for adults. Nonetheless, fluency is possible, even if a learner does not fully acquire the phonology. As we have explored, it is perhaps not always ideal to completely emulate native-level speech. The fact that progress is inevitable with hard work is a gift which only adult learners can enjoy. While children cannot understand the power of their natural talents, all adults understand that hard work pays off. It is this wisdom which gives adult learners a unique advantage.
Make the most of your language learning efforts with Clozemaster - thousands of sentences in over 50 languages!

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Language Learning in Adulthood - Advantages, Disadvantages, and Getting Fluent Faster

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Where a child can learn a language relatively easily, language learning in adulthood can be a difficult task. This article examines the difficulties that adults can face in learning a language and demonstrates that some of an adult's innate weaknesses can actually be an advantage.

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It shows six important step of how adults learn language young children. Benny Lewis note "Adults are more motivated to learn than children"

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Fluent in 3 months - Language Hacking and Travel Tips

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by Benny Lewis

"I'll never learn to run with the stamina of Paula Radcliffe, so why bother training for a marathon?"

"I'll never win a Nobel Prize in maths, so what's the point of studying it at all?"

"I'll never play cello like Yo-Yo Mah, so I shouldn't even start."

How do these excuses sound to you? If, like me, you love to learn for the sake of learning, they probably sound quite lame.

Yet so many language learners let themselves be swayed by similar excuses:

"I don't have the language gene."

"I'll never have a perfect French accent."

"I'm too old to ever be fluent in a new language"

"I didn't do it as a child, so why start now?"

The "I'm too old" excuse is one I hear a lot. I even said it to myself as a young adult, when I still only spoke one language fluently. Now, over a decade later, I'm fluent in seven languages.

Putting aside the fact that there's no conclusive proof that children learn languages any better than adults, would it really matter if they did? Children are good at learning languages. They're good at learning, full stop. But adults are absolutely not bad at learning. In fact, they're extremely good at it. Just look around the web at all the people who have successfully reached fluency, even mastery, in another language well into adulthood with no previous foreign language experience.

With that in mind, I've investigated how adults learn - from a scientific point of view. You can use these insights to your advantage when hashing out a study plan for your target language.

1. The Ability to Learn Vocabulary is not Related to Age

Whatever advantages children may have in language acquisition, such as more easily learning to speak without an accent, they don't have an advantage where it counts: learning the actual words required to speak a language.

Vocabulary is far more important to learning a language than accent. In fact, accent isn't an indicator at all of your competence with a language, regardless of some people's preconceived notions to the contrary.

What's more, as an adult, you can use hacks for memorising vocabulary quickly, which I'd argue work even better as an adult. Adults have more life experience and can invent more memorable stories as mnemonics to make the new vocabulary stick.

If a native accent is one of your goals, go for it! A good accent can change people's perception of you, even if you don't speak the language any better than someone with a foreign accent. A native-sounding accent is not impossible, no matter how old you are. It just takes a bit more effort. Which brings me to my next point...

2. Adults are More Motivated to Learn than Children

If you're an adult thinking about learning a second language, chances are, it's not out of necessity (though obviously for a small percentage of people, it is). It's morely likely that you want to learn a new language for some personal motivation. Perhaps to experience other cultures in a more authentic way, to appreciate the arts and literature of another country, or to keep your mind sharp.

On the other hand, how many kids do you know who like to do extra homework after school when they don't have to? Not many, I'd guess! The only reason most kids go to school and do homework at all is because they're sent there by their parents. When you reach adulthood, however, you realise the benefits of learning for the sheer pleasure of it. As a result, you're more motivated. This extra motivation means learning more quickly and efficiently. Consequently, the learning process itself becomes more enjoyable.

Not only are adults more motivated to learn for learning's sake, but also because of the immediate reward they get from learning something new, which children don't get. And that is...

3. Adults Get to Immediately Apply What They've Learned

When you were a kid in school, I bet you wondered more than once why you had to multiply compound fractions, or learn verb conjugations for a language you wouldn't be able to use outside of class for years and years, if ever. None of what you were learning was relevant to your day-to-day kid life, so you didn't see the big picture about why it was useful. That's understandable! It's not easy for anyone, much less a child, to enthusiastically learn something that they won't use for ten or twenty years!

You have a big advantage as an adult, however, in that you can get out there today and practise the things you learned yesterday. There are few places where this is more evident than in language learning. Unlike many other disciplines, you don't have to wait until you're ready before you go out and speak a language. Even if you only know ten words, you can go out on day one and use those ten words to successfully communicate with native speakers.

When you're able to see such immediate success, you're far more likely to continue studying. Compare this with children who have to sit in a classroom for years, memorising vocabulary like "stapler", "moose", and a host of other words that are irrelevant to daily life, for the sole purpose of passing a test. No wonder so many children drop their second language course at the first chance.

As an adult, you can forget about staplers and moose and just learn the vocabulary that's relevant to you right now, giving you the ability to instantly go and have a conversation in your target language using that vocabulary. You can learn whatever and however you want, and still get the most out of your studying, because...

4. Adults Have Control Over Their Learning Environment

I love being an adult! I'm all grown up, settled down, and exceptionally mature for my age. Well, ok, I'm all grown up at least!

Grown-ups have something that children don't: control over their daily lives. If you want cake for supper, you can eat as much cake as you like.

You also have control over your learning environment as an adult. When studying your target language, you get to experiment and find out how you learn best. Then you can go ahead and learn that way. No more relying exclusively on teachers with pre-determined lesson plans that offer no flexibility in what you learn, or how you learn it. I'm sure there are some people out there who learn languages best in a classroom, but if (like me) you're not one of them, then you might have fooled yourself as a child into thinking that you were no good at languages.

Now that you're an adult, you'll see that there are nearly as many ways to effectively learn a language as there are language learners. All it takes is a bit of trial and error to find the combination of language hacks that works best for you.

And once you start studying a new language, you'll quickly gain momentum in your learning. The reason for this is...

5. The More Adults Learn, The Easier Learning Becomes

One of the reasons adults supposedly learn more slowly is simply because they're out of practice. The phrase "use it or lose it" couldn't be more apt when it comes to your brain.

Every time you learn something new, you create new synapses and increase the plasticity of your brain. This makes it easier for you to retain the skills you've learned, improve on these skills, and continue learning new things. That's why I can go for months without practising some of my languages, but can then spend just a few days polishing up the areas where I'm rusty, and get right back to the level I was at before.

If you don't use a skill for a while, but you spend the meantime using your brain to learn other skills (such as another language, a musical instrument, or even juggling) then what you're doing is improving your ability to learn. As a result, you can re-learn the old skill more quickly, as well as more easily learn entirely new skills. You'll gain momentum. You'll see results more quickly, and get hooked on learning. It will become a lifelong process.

When it comes to learning a language, however, just practising over and over again, like you would practise the piano, isn't really effective. You'll want to use your language in interactive ways in order to improve. Which brings me to my final point...

6. Adults Learn Languages Faster When They Get Feedback

This should be no surprise. However much you might consider yourself shy and introverted, best suited to studying alone at home, there's simply no substitute for interactive feedback in your language learning. The easiest and most efficient way to get it is by talking with real people in your target language.

If you only practise by yourself at home for hours, without getting any real feedback about your progress, then don't be surprised if you fail to meet your language goals and end up losing motivation. Don't get me wrong: tools like Duolingo and spaced repetition software are an extremely useful supplement to your language learning. You can use them to study vocabulary and grammar. But if you want to be sure that you're actually using the language correctly, talk with a native speaker who can provide feedback. Not only will you learn to use the language more effectively, you'll get a better ear for it and start to pronounce it more closely to native speech.

How Adults Learn: Your Attitude is a far Better Predictor of Success than Your Age

You can learn a language at any age. Sixteen or sixty! If you want to learn a new language but have yet to begin, then the only thing holding you back is your mindset. Like the old saying goes: "Whether you think you can, or you think you can't, you're right ".

Yes, your individual results might vary compared to other people's, but guess what? No matter how good you are, there will always be someone better. You're never going to be the very best in the world at anything - especially languages. But why worry about that?

Stop comparing yourself to others. Stop making excuses. Get out there and learn something!

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How Adults Learn: 6 Important Things to Know

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by Benny Lewis "I'll never learn to run with the stamina of Paula Radcliffe, so why bother training for a marathon?" "I'll never win a Nobel Prize in maths, so what's the point of studying it at all?" "I'll never play cello like Yo-Yo Mah, so I shouldn't even start."

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William, Alexander. "The Benefits of Failing at French". Learning a second language as an adult is really challenging. The older you get the harder it is to learn a language. William note that "All this means that we adults have to work our brains hard to learn a second language."

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Op-Ed Contributor

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Credit Credit Jason Logan

I USED to joke that I spoke French like a 3-year-old. Until I met a French 3-year-old and couldn't hold up my end of the conversation. This was after a year of intense study, including at least two hours a day with Rosetta Stone, Fluenz and other self-instruction software, Meetup groups, an intensive weekend class and a steady diet of French movies, television and radio, followed by what I'd hoped would be the coup de grâce: two weeks of immersion at one of the top language schools in France.

"French resistance" took on an entirely new meaning as my brain repelled every strategy I employed. Yet my failure was in fact quite unremarkable. Advertising claims notwithstanding, few adults who tackle a foreign language achieve anything resembling proficiency. In the end, though, it turns out that spending a year not learning French may have been the best thing I could've done for my 57-year-old brain.

In the last few years, unable to hold a list of just four grocery items in my head, I'd begun to fret a bit over my literal state of mind. So to reassure myself that nothing was amiss, just before tackling French I took a cognitive assessment called CNS Vital Signs, recommended by a psychologist friend. The results were anything but reassuring: I scored below average for my age group in nearly all of the categories, notably landing in the bottom 10th percentile on the composite memory test and in the lowest 5 percent on the visual memory test.

This, obviously, did not bode well for my nascent language project, but I forged ahead. To be sure, learning a foreign language is a daunting task for any adult. How can something that a toddler accomplishes before learning to tie his shoes be so difficult for grown-ups?

Psycholinguists are divided on the answer, but they agree on several points. For starters, a 2-year-old's brain has a substantial neurological advantage, with 50 percent more synapses - the connections between neurons - than an adult brain, way more than it needs. This excess, which is an insurance policy against early trauma, is also crucial to childhood language acquisition, as is the plasticity, or adaptability, of the young brain.

Once the "critical period" - the roughly six years of life during which the brain is wired for learning language - is over, the ability to acquire a first language is lost, as your brain frees up room for the other skills you'll need as you mature, such as the ability to kill a wild boar, or learn math, or operate your iPad.

Another advantage a toddler holds is his very lack of experience. After speaking our native language for decades, we adults can't help but hear the second language through the filter of the first. And this filter doesn't take decades to develop. Researchers have found that newborn Japanese babies can distinguish between the English "L" and "R" sounds, but if not exposed to Western languages, they begin to lose that ability - not by the age of 6 or even 3 - but by eight months.

Adult language learners are, to borrow a phrase used by some psycholinguists, too smart for our own good. We process too much data at once, try to get everything right from the get-go and are self-conscious about our efforts. But toddlers instinctively grasp what's important and are quite content to say, "Tommy hitted me," as long as Tommy gets what's coming to him.

All this means that we adults have to work our brains hard to learn a second language. But that may be all the more reason to try, for my failed French quest yielded an unexpected benefit. After a year of struggling with the language, I retook the cognitive assessment, and the results shocked me. My scores had skyrocketed, placing me above average in seven of 10 categories, and average in the other three. My verbal memory score leapt from the bottom half to the 88th - the 88th! - percentile and my visual memory test shot from the bottom 5th percentile to the 50th. Studying a language had been like drinking from a mental fountain of youth.

What might explain such an improvement?

Last year researchers at the Chinese University of Hong Kong and Northwestern University in Illinois hypothesized that language study should prove beneficial for older adults, noting that the cognitive tasks involved - including working memory, inductive reasoning, sound discrimination and task switching - map closely to the areas of the brain that are most associated with declines due to aging. In other words, the things that make second-language acquisition so maddening for grown-ups are the very things that may make the effort so beneficial.

The quest for a mental fountain of youth, pursued by baby boomers who fear that their bodies will outlive their brains, and who have deeper pockets than Juan Ponce de León, has created a billion-dollar industry. There is some evidence that brain exercise programs like Lumosity and Nintendo's Brain Age can be beneficial, but if my admittedly unscientific experience is any indication, you might be better off studying a language instead. Not only is that a far more useful and enjoyable activity than an abstract brain game, but as a reward for your efforts, you can treat yourself to a trip abroad. Which is why I plan to spend the next year not learning Italian. Ciao!

William Alexander is the author of the forthcoming book "Flirting With French: How a Language Charmed Me, Seduced Me, and Nearly Broke My Heart."

A version of this article appears in print on , Section A, Page 23 of the New York edition with the headline: The Benefits of Failing at French. Order Reprints | Today's Paper | Subscribe

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Opinion | The Benefits of Failing at French

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Op-Ed Contributor I USED to joke that I spoke French like a 3-year-old. Until I met a French 3-year-old and couldn't hold up my end of the conversation.

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Adult brain remains plastic and it can reconfigure its own circuity as its neural liveware.
Eagleman write "By the time we're twenty-five years of age, the brain transformations of childhood and adolescence are finally over"

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Read 1,725 reviews from the world's largest community for readers. Locked in the silence and darkness of your skull, your brain fashions the rich narrative...