A critical period for second language acquisition: Evidence from 2/3 million English speakers

Research has consistently shown there is a negative correlation between age of onset (AO) of acquisition and ultimate attainment (UA) of either pronunciation or grammar in a second language (L2). A few studies have indeed reported nativelike behavior in some postpuberty learners with respect to either phonetics/phonology or morphosyntax, a result that has sometimes been taken as evidence against the critical period hypothesis (CPH). However, in the few studies that have employed a wide range of linguistic tests and tasks, adult learners have not exhibited nativelike L2 proficiency across the board of measures, which, according to some, suggests that the hypothesis still holds. The present study investigated the relationship between AO and UA and the incidence of nativelikeness when measures of phonetic and grammatical intuition are combined. An additional aim was to investigate whether children and adults develop the L2 through fundamentally different brain mechanisms—namely, whether children acquire the language (more) implicitly as an interdependent whole, whereas adults learn it (more) explicitly as independent parts of a whole.

This article provides a selective overview of theoretical issues and empirical findings relating to the question of age and second language acquisition (L2A). Both behavioral and brain-based data are discussed in the contexts of neurocognitive aging and cognitive neurofunction in the mature individual. Moving beyond the classical notion of “deficient” L2 processing and acquisition, we consider the complementary question of learner potential in postadolescent L2A.

It has been difficult to determine how cognitive systems change over the grand time scale of an entire life, as few cognitive systems are well enough understood; observable in infants, adolescents, and adults; and simple enough to measure to empower comparisons across vastly different ages. Here we address this challenge with data from more than 10,000 participants ranging from 11 to 85 years of age and investigate the precision of basic numerical intuitions and their relation to students’ performance in school mathematics across the lifespan. We all share a foundational number sense that has been observed in adults, infants, and nonhuman animals, and that, in humans, is generated by neurons in the intraparietal sulcus. Individual differences in the precision of this evolutionarily ancient number sense may impact school mathematics performance in children; however, we know little of its role beyond childhood. Here we find that population trends suggest that the precision of one’s number sense improves throughout the school-age years, peaking quite late at ∼30 y. Despite this gradual developmental improvement, we find very large individual differences in number sense precision among people of the same age, and these differences relate to school mathematical performance throughout adolescence and the adult years. The large individual differences and prolonged development of number sense, paired with its consistent and specific link to mathematics ability across the age span, hold promise for the impact of educational interventions that target the number sense.

Abstract The representation of L2 words and non-words was analysed in a series of three experiments. Catalan-Spanish bilinguals, differing in terms of their L1 and the age of exposure to their L2 (since birth—simultaneous bilinguals—or starting in early childhood—early sequential bilinguals), were asked to perform a lexical decision task on Catalan words and non-words. The non-words were based on real words, but with one vowel changed: critically, this vowel change could involve a Catalan contrast that Spanish natives find difficult to perceive. The results confirmed previous data indicating that in spite of early, intensive exposure, Spanish-Catalan bilinguals fail to perceive certain Catalan contrasts, and that this failure has consequences at the lexical level. Further, the results from simultaneous bilinguals show: (a) that even in the case of bilinguals who are exposed to both languages from birth, a dominant language prevails; and (b) that simultaneous bilinguals do not attain the same level of proficiency as early bilinguals in their first language.

The proposal is made that the interface between language and theory of mind is bidirectional. It seems probable that the conceptual developments of early Theory of Mind form an essential basis for helping to fix at least word reference. In development from two to four years, no basis exists in research for conclusions about the direction of influence between language and Theory of Mind. At the stage of false belief reasoning, after age four, the role of the mastery of syntactic complementation is highlighted as a representational tool, that is, language development assists reasoning. The paper presents a brief summary of Theory of Mind, ranging from its earliest beginnings in infancy to the appreciation around age four years that others might hold false beliefs and act according to them. For each development, the parallel language developments are described, and questions are raised about the interface between the two. In particular, research that might determine the direction of influence from one to the other is discussed. More work is called for, especially with nonverbal tasks, good experimental linguistic work, and other special populations, that might allow a more precise delineation of how language and Theory of Mind interrelate at the interface.

SNOW, CATHERINE E., and HOEFNAGEL-H6HLE, MARIAN. The Critical Period for Language Acquistion: Evidence from Second Language Learning. CHILD DEVELOPMENT, 1978, 49, 1114-1128. The critical period hypothesis holds that first language acquisition must occur before cerebral lateralization is complete, at about the age of puberty. One prediction of this hypothesis is that second language acquisition will be relatively fast, successful, and qualitatively similar to first language only if it occurs before the age of puberty. This prediction was tested by studying longitudinally the naturalistic acquisition of Dutch by English speakers of different ages. The subjects were tested 3 times during their first year in Holland, with an extensive test battery designed to assess several aspects of their second language ability. It was found that the subjects in the age groups 12-15 and adult made the fastest progress during the first few months of learning Dutch and that at the end of the first year the 8-10and 12-15-year-olds had achieved the best control of Dutch. The 3-5-year-olds scored lowest on all the tests employed. These data do not support the critical period hypothesis for language acquisition.

This paper suggests that there are constraints on learning required to explain the acquisition of language, in particular, mului ultonol constraints. First, empirical evidence for this daim is reviewed. The evidence from several studies of both first and second languoge acquisition suggests that normal language learning occurs only when exposure to the languoge begins early in life. With exposure beginning later in life, asymptotic performance in the language declines: the effects over oge of first exposure are approximately linear through childhood, with a flattening of the function in adulthood. These outcomes argue that some type of constraints ensuring successful languoge learning exist early in life, and weaken with increasing maturation. Second, two hypotheses are considered as to the nature of these maturational changes. One hypothesis is that constraints on learning particular to languoge acquisition undergo maturational decay. A second hypothesis, which is considered in more detail, suggests that language learning abilities decline because of the expansion of nonlinguisftc cognitive abilities.

Three groups of participants were given a grammaticality judgement test based on five structures of English grammar in both an oral and written form. The first group consisted of native speakers of Chinese, the second, native speakers of Spanish, and the third, native English speakers. The two learner groups were divided into those who had begun learning English at a younger (less than 15 years) or older (more than 15 years) age. Performance was measured for both accuracy of judgement and time taken to respond. The results showed that performance patterns were different for the two learner groups, that the linguistic structure tested in the item affected participants' ability to respond correctly, and that task modality produced reliable response differences for the two learner groups. Although there were proficiency differences in the grammaticality judgement task between the younger and older Spanish learners, there were no such differences for the Chinese group. Furthermore, age of learning influenced achieved proficiency through all ages tested rather than defining a point of critical period. The results are interpreted as failing to provide sufficient evidence to accept the hypothesis that there is a critical period for second language acquisition.

Second-language (L2) acquisition is generally thought to be constrained by maturational factors that circumscribe a critical period for nativelike attainment. Consistent with the maturational view are age effects among learners who begin L2 acquisition prior to, but not after, closure of the putative critical period. Also favoring the maturational account is the scarcity of late L2 learners at asymptote who perform like natives, and weak effects of native language‐target language pairings. With Korean and Chinese learners of English, the experimental study of Johnson and Newport (1989) yielded just these types of evidence. Some subsequent studies do not support the critical period account of L2 acquisition constraints, however. Accordingly, we undertook a replication of Johnson and Newport (1989), using the exact methods and materials of the original experiment, and a sample of Spanish natives (n = 61). In keeping with recent research, L2 attainment negatively correlates with age of learning even if learning commences after the presumed end of the critical period. We also find modest evidence of nativelike attainment among late learners. Our data further suggest that the outcome of L2 acquisition may depend on L1‐L2 pairings and L2 use. © 2001 Academic Press

Native Spanish early and late acquirers of English as well as native Vietnamese early and child acquirers of English made grammaticality judgments of sentences in their second language. Native Spanish early acquirers were not distinguishable from native English speakers, whereas native Spanish late acquirers had difficulty with all aspects of the grammar tested except word order. Native Vietnamese early acquirers had difficulty with those aspects of English that differ markedly from Vietnamese. Native Vietnamese child acquirers had more generalized problems, similar to those of native Spanish late acquirers. Thus, native language appeared to make a difference for early acquirers, whereas a later age of acquisition caused a more general problem. A processing-based model focusing on the difficulty non-native language learners have in rapidly decoding surface form is offered as a possible explanation for both effects.

Recent research observed a sensitive window, at about 14 years of age, in the acculturation rates of Chinese immigrants to Canada. Tapping an online sample of us immigrants ( n =569), we tested these relationships in a broader population and explored connections with new potentially causally related variables: formal education, language ability and contact with heritage-culture and mainstream United States individuals, both now and at immigration. While we found that acculturation decreased with age at immigration and increased with years in the us , we did not observe a similar sensitive window (i.e., change in rate with age). We also present an exploratory path analysis, exposing the relationships in our sample between acculturation and the variables above. The novel relationships documented here can improve theorising about this rich and complex empirical phenomenon.

In second language acquisition research, the critical period hypothesis (cph) holds that the function between learners' age and their susceptibility to second language input is non-linear. This paper revisits the indistinctness found in the literature with regard to this hypothesis's scope and predictions. Even when its scope is clearly delineated and its predictions are spelt out, however, empirical studies-with few exceptions-use analytical (statistical) tools that are irrelevant with respect to the predictions made. This paper discusses statistical fallacies common in cph research and illustrates an alternative analytical method (piecewise regression) by means of a reanalysis of two datasets from a 2010 paper purporting to have found cross-linguistic evidence in favour of the cph. This reanalysis reveals that the specific age patterns predicted by the cph are not cross-linguistically robust. Applying the principle of parsimony, it is concluded that age patterns in second language acquisition are not governed by a critical period. To conclude, this paper highlights the role of confirmation bias in the scientific enterprise and appeals to second language acquisition researchers to reanalyse their old datasets using the methods discussed in this paper. The data and R commands that were used for the reanalysis are provided as supplementary materials.

Functional maturation of visual cortex is linked with dynamic changes in synaptic expression of GABAergic mechanisms. These include setting the excitation-inhibition balance required for experience-dependent plasticity, as well as, intracortical inhibition underlying development and aging of receptive field properties. Animal studies have shown developmental regulation of GABAergic mechanisms in visual cortex. In this study, we show for the first time how these mechanisms develop in the human visual cortex across the lifespan. We used Western blot analysis of postmortem tissue from human primary visual cortex (n=30, range: 20 days to 80 years) to quantify expression of 8 pre- and post-synaptic GABAergic markers. We quantified the inhibitory modulating cannabinoid receptor (CB1), GABA vesicular transporter (VGAT), GABA synthesizing enzymes (GAD65/GAD67), GABAA receptor anchoring protein (Gephyrin), and GABAA receptor subunits (GABAA∝1, GABAA∝2, GABAA∝3). We found a complex pattern of changes, many of which were prolonged and continued well into into the teen, young adult, and even older adult years. These included a monotonic increase or decrease (GABAA∝1, GABAA∝2), a biphasic increase then decrease (GAD65, Gephyrin), or multiple increases and decreases (VGAT, CB1) across the lifespan. Comparing the balances between the pre- and post-synaptic markers we found 3 main transitions (early childhood, early teen years, aging) when there were rapid switches in the composition of the GABAergic signaling system, indicating that functioning of the GABAergic system must change as the visual cortex develops and ages. Furthermore, these results provide key information for translating therapies developed in animal models into effective treatments for amblyopia in humans.

Age of onset and nativelikeness in a second language: listener perception versus linguistic scrutiny

In the field of psychology, the practice of p value null-hypothesis testing is as widespread as ever. Despite this popularity, or perhaps because of it, most psychologists are not aware of the statistical peculiarities of the p value procedure. In particular, p values are based on data that were never observed, and these hypothetical data are themselves influenced by subjective intentions. Moreover, p values do not quantify statistical evidence. This article reviews these p value problems and illustrates each problem with concrete examples. The three problems are familiar to statisticians but may be new to psychologists. A practical solution to these p value problems is to adopt a model selection perspective and use the Bayesian information criterion (BIC) for statistical inference (Raftery, 1995). The BIC provides an approximation to a Bayesian hypothesis test, does not require the specification of priors, and can be easily calculated from SPSS output.

The myelin content of the cortex changes over the human lifetime and aberrant cortical myelination is associated with diseases such as schizophrenia and multiple sclerosis. Recently magnetic resonance imaging (MRI) techniques have shown potential in differentiating between myeloarchitectonically distinct cortical regions in vivo. Here we introduce a new algorithm for correcting partial volume effects present in mm-scale MRI images which was used to investigate the myelination pattern of the cerebral cortex in 1555 clinically normal subjects using the ratio of T1-weighted (T1w) and T2-weighted (T2w) MRI images. A significant linear cross-sectional age increase in T1w/T2w estimated myelin was detected across an 18 to 35 year age span (highest value of ~ 1%/year compared to mean T1w/T2w myelin value at 18 years). The cortex was divided at mid-thickness and the value of T1w/T2w myelin calculated for the inner and outer layers separately. The increase in T1w/T2w estimated myelin occurs predominantly in the inner layer for most cortical regions. The ratio of the inner and outer layer T1w/T2w myelin was further validated using high-resolution in vivo MRI scans and also a high-resolution MRI scan of a postmortem brain. Additionally, the relationships between cortical thickness, curvature and T1w/T2w estimated myelin were found to be significant, although the relationships varied across the cortex. We discuss these observations as well as limitations of using the T1w/T2w ratio as an estimate of cortical myelin. • Without partial volume correction T1w/T2w myelination may be overestimated. • Average myelin maps presented for 1555 clinically normal 18–35 year old subjects. • Inner cortical layers show higher T1w/T2w myelination compared to outer layers. • T1w/T2w myelination of the cortex increases with age between 18 and 35 years. • Age-dependent increase of myelination occurs mostly in the inner cortical layers.

Current investigators of words, sentences, and other language materials almost never provide statistical evidence that their findings generalize beyond the specific sample of language materials they have chosen. Nevertheless, these same investigators do not hesitate to conclude that their findings are true for language in general. In so doing, it is argued, they are committing the language-as-fixed-effect fallacy, which can lead to serious error. The problem is illustrated for one well-known series of studies in semantic memory. With the appropriate statistics these studies are shown to provide no reliable evidence for most of the main conolusions drawn from them. A review of other experiments in semantic memory shows that many of them are likewise suspect. It is demonstrated how this fallacy can be avoided by doing the right statistics, selecting the appropriate design, and sampling by systematic procedures, or, alternatively, by proceeding according to the so-called method of single cases.

Changes in several postnatal maturational processes during neural development have been implicated as potential mechanisms underlying critical period phenomena. Lenneberg hypothesized that maturational processes similar to those that govern sensory and motor development may also constrain capabilities for normal language acquisition. Our goal, using a bilingual model, was to investigate the hypothesis that maturational constraints may have different effects upon the development of the functional specializations of distinct sub within language. Subjects were 61 adult Chinese/English bilinguals who were exposed to English at different points in development: 1-3, 4-6, 7-10, 11-13, and after 16 years of age. Event-related brain potentials (ERPs) and behavioral responses were obtained as subjects read sentences that included semantic anomalies, three types of syntactic violations (phrase structure, specificity constraint, and subjacency constraint), and their controls. The accuracy in judging the grammaticality for the different types of syntactic rules and their associated ERPs was affected by delays in second language exposure as short as 1-3 years. By comparison the N400 response and the judgment accuracies in detecting semantic anomalies were altered only in subjects who were exposed to English after 11-13 and 16 years of age, respectively. Further, the type of changes occurring in ERPs with delays in exposure were qualitatively different for semantic and syntactic processing. All groups displayed a significant N400 effect in response to semantic anomalies, however, the peak latencies of the N400 elicited in bilinguals who were exposed to English between 11-13 and >16 years occurred later, suggesting a slight slowing in processing. For syntactic processing. the ERP differences associated with delays in exposure to English were observed in the morphology and distribution of components. Our findings are consistent with the view that maturational changes significantly constrain the development of the neural systems that are relevant for language and, further, that subsystems specialized for processing different aspects of language display different sensitive periods.

(1) Adults proceed through early stages of syntactic and morphological development faster than children (where time and exposure are held constant). (2) Older children acquire faster than younger children (again, in early stages of morphological and syntactic development where time and exposure are held constant). (3) Acquirers who begin natural exposure to second languages during childhood generally achieve higher second language proficiency than those beginning as adults.

In this paper we specify language acquisition processes in terms of brain mechanisms in order to explain the variable success achieved by early and late language learners. On the basis of the literature in language acquisition, neurobiology, and linguistics, we propose a brain-based model for language acquisition. The model assumes two conditions must be met in order to acquire full knowledge of a particular language: first, that the learner is motivated to acquire the language; and second, that the learner is equipped with the ability to acquire grammatical knowledge. We explain the neural underpinnings for both motivation and grammatical ability and show how they interact to produce variable success in language acquisition.

This study examined the variables related to US immigrants' long-term attainment in English, their second language (L2), and their native language (L1). For 44 Mandarin–English bilinguals, with increasing age of arrival (AOA) in the United States, their accuracy in L2 grammaticality judgment tasks decreased and accuracy in an L1 grammaticality judgment task increased. Moreover, both AOA in the United States and mothers' English proficiency uniquely predicted a significant proportion of the variance for bilinguals' L2 proficiency. Finally, as a group, 72 speakers of three Asian languages showed lower levels of L2 proficiency and stronger AOA effects on the task performance than 32 speakers of six European languages. These differences in language proficiency were associated with differences in language use, language learning motivation, and cultural identification between the two groups. These findings suggest that L2 acquisition in the immigration setting is a complicated process involving the dynamic interactions of multiple variables.

For more than 100 years, the scientific and educational communities have thought that age is critical to the outcome of language learning, but whether the onset and type of language experienced during early life affects the ability to learn language is unknown. Here we show that deaf and hearing individuals exposed to language in infancy perform comparably well in learning a new language later in life, whereas deaf individuals with little language experience in early life perform poorly, regardless of whether the early language was signed or spoken and whether the later language was spoken or signed. These findings show that language-learning ability is determined by the onset of language experience during early brain development, independent of the specific form of the experience.

This study critically examines the widespread practice of comparing the linguistic processes and representations of non-native speakers with those of natives. We argue that, in some respects, the method yields benefits, while in others it does not serve the interests of research into the nature of second language acquisition and bilingualism. We go on to consider certain analytical approaches that skirt the hazards of the method. The potential payoffs of native/non-native comparisons are illustrated in a priming study of monolingual and bilingual processing of ambiguity in complex French syntax (Gertken 2013).

This study determined whether the long-range outcome of first-language acquisition, when the learning begins after early childhood, is similar to that of second-language acquisition. Subjects were 36 deaf adults who had contrasting histories of spoken and sign language acquisition. Twenty-seven subjects were born deaf and began to acquire American Sign Language (ASL) as a first language at ages ranging from infancy to late childhood. Nine other subjects were born with normal hearing, which they lost in late childhood; they subsequently acquired ASL as a second language (because they had acquired spoken English as a first language in early childhood). ASL sentence processing was measured by recall of long and complex sentences and short-term memory for signed digits. Subjects who acquired ASL as a second language after childhood outperformed those who acquired it as a first language at exactly the same age. In addition, the performance of the subjects who acquired ASL as a first language declined in association with increasing age of acquisition. Effects were most apparent for sentence processing skills related to lexical identification, grammatical acceptability, and memory for sentence meaning. No effects were found for skills related to fine-motor production and pattern segmentation.

Hartshorne and Ullman (2006) presented naturalistic language data from 25 children (15 boys, 10 girls) and showed that girls produced more past tense overregularization errors than did boys. In particular, girls were more likely to overregularize irregular verbs whose stems share phonological similarities with regular verbs. It was argued that the result supported the Declarative/Procedural model of language, a neuropsychological analogue of the dual-route approach to language. In the current study we present experimental data that are inconsistent with these naturalistic data. Eighty children (40 males, 40 females) aged 5;0-6;9 completed a past tense elicitation task, a test of declarative memory, and a test of non-verbal intelligence. The results revealed no sex differences on any of the measures. Instead, the best predictors of overregularization rates were item-level features of the test verbs. We discuss the results within the context of dual versus single route debate on past tense acquisition.

Children extend regular grammatical patterns to irregular words, resulting in overregularizations like comed, often after a period of correct performance ("U-shaped development"). The errors seem paradigmatic of rule use, hence bear on central issues in the psychology of rules: how creative rule application interacts with memorized exceptions in development, how overgeneral rules are unlearned in the absence of parental feedback, and whether cognitive processes involve explicit rules or parallel distributed processing (connectionist) networks. We remedy the lack of quantitative data on overregularization by analyzing 11,521 irregular past tense utterances in the spontaneous speech of 83 children. Our findings are as follows. (1) Overregularization errors are relatively rare (median 2.5% of irregular past tense forms), suggesting that there is no qualitative defect in children's grammars that must be unlearned. (2) Overregularization occurs at a roughly constant low rate from the 2s into the school-age years, affecting most irregular verbs. (3) Although overregularization errors never predominate, one aspect of their purported U-shaped development was confirmed quantitatively: an extended period of correct performance precedes the first error. (4) Overregularization does not correlate with increases in the number or proportion of regular verbs in parental speech, children's speech, or children's vocabularies. Thus, the traditional account in which memory operates before rules cannot be replaced by a connectionist alternative in which a single network displays rotelike or rulelike behavior in response to changes in input statistics. (5) Overregularizations first appear when children begin to mark regular verbs for tense reliably (i.e., when they stop saying Yesterday I walk). (6) The more often a parent uses an irregular form, the less often the child overregularizes it. (7) Verbs are protected from overregularization by similar-sounding irregulars, but they are not attracted to overregularization by similar-sounding regulars, suggesting that irregular patterns are stored in an associative memory with connectionist properties, but that regulars are not. We propose a simple explanation. Children, like adults, mark tense using memory (for irregulars) and an affixation rule that can generate a regular past tense form for any verb. Retrieval of an irregular blocks the rule, but children's memory traces are not strong enough to guarantee perfect retrieval. When retrieval fails, the rule is applied, and overregularization results.

ABSTRACT Few researchers would doubt that ultimate attainment in second language grammar is negatively correlated with age of acquisition, but considerable controversy remains about the nature of this relationship: the exact shape of the age-attainment function and its interpretation. This article presents two parallel studies with native speakers of Russian: one on the acquisition of English as a second language in North America ( n = 76), and one on the acquisition of Hebrew as a second language in Israel ( n = 64). Despite the very different nature of the languages being learned, the two studies show very similar results. When age at testing is partialed out, the data reveal a steep decline in the learning of grammar before age 18 in both groups, followed by an essentially horizontal slope until age 40. This is interpreted as evidence in favor of the critical period. Both groups show a significant correlation between ultimate attainment and verbal aptitude for the adult learners, but not for the early learners. This is interpreted as further evidence that the learning processes in childhood and adulthood not only yield different levels of proficiency but are also different in nature.

Abstract The general question raised here is why the young child is superior to older children and adults at language acquisition, while at the same time inferior to them in many other cognitive tasks. As an example of the general problem, the paper reviews our own work on the acquisition of complex verbs of American Sign Language (ASL). It begins with an outline of the structure of verbs of motion in ASL, along with possible inductive generalizations a language learner might make concerning this structure. Three lines of research on ASL acquisition are then presented. The first line of research demonstrates that young children, exposed to ASL as a native language, acquire ASL verbs in terms of morphological components, piece by piece, as do children learning spoken language. Moreover, they do so despite alternative generalizations which seem potentially simpler. The second line of research compares native learners of ASL with learners exposed to ASL later in life. This research shows that, while native learners make the morphological componential generalization described, later learners in fact do make alternative generalizations. The third line of research investigates native learners of ASL whose parental input models are late learners. Again it appears that natives perform a morphological analysis, despite the fact that their input is not well organized for such analyses. Taken together, the research shows a striking tendency for children—and only children—to acquire language in a particular fashion. The paper concludes with a discussion of possible explanations for these findings. One possibility is that children have a special set of skills for language acquisition which declines with age. A second possibility is that the cognitive limitations of the child provide the basis on which the child's componential learning occurs, and that the expansion of these cognitive abilities with age is in part responsible for the decline in this type of learning.

This research tested the hypothesis that learners whose exposure to a second language begins before the age of 15 years achieve higher syntactic proficiency in the target language than adult learners. Sixty-seven immigrants who had come to the United States at various ages and who had resided in this country for various periods of time were tested for syntactic proficiency in English and were also administered a questionnaire to gather information concerning practice and instructional variables. Age at arrival was found to be a strong predictor of syntactic proficiency while other independent variables had very little effect. The results were interpreted as providing support for the hypothesis of an age related limitation on the ability to acquire full command of syntax in a second language.

Research on age-related cognitive change traditionally focuses on either development or aging, where development ends with adulthood and aging begins around 55 years. This approach ignores age-related changes during the 35 years in-between, implying that this period is uninformative. Here we investigated face recognition as an ability that may mature late relative to other abilities. Using data from over 60,000 participants, we traced the ability to learn new faces from pre-adolescence through middle age. In three separate experiments, we show that face learning ability improves until just after age 30 - even though other putatively related abilities (inverted face recognition and name recognition) stop showing age-related improvements years earlier. Our data provide the first behavioral evidence for late maturation of face processing and the dissociation of face recognition from other abilities over time demonstrates that studies on adult age development can provide insight into the organization and development of cognitive systems.

This article describes the R package <b>DEoptim</b>, which implements the differential evolution algorithm for global optimization of a real-valued function of a real-valued parameter vector. The implementation of differential evolution in <b>DEoptim</b> interfaces with C code for efficiency. The utility of the package is illustrated by case studies in fitting a Parratt model for X-ray reflectometry data and a Markov-switching generalized autoregressive conditional heteroskedasticity model for the returns of the Swiss Market Index.

A new method is presented for flexible regression modeling of high dimensional data. The model takes the form of an expansion in product spline basis functions, where the number of basis functions as well as the parameters associated with each one (product degree and knot locations) are automatically determined by the data. This procedure is motivated by the recursive partitioning approach to regression and shares its attractive properties. Unlike recursive partitioning, however, this method produces continuous models with continuous derivatives. It has more power and flexibility to model relationships that are nearly additive or involve interactions in at most a few variables. In addition, the model can be represented in a form that separately identifies the additive contributions and those associated with the different multivariable interactions.

Adolescence is a period of formative biological and social transition. Social cognitive processes involved in navigating increasingly complex and intimate relationships continue to develop throughout adolescence. Here, we describe the functional and structural changes occurring in the brain during this period of life and how they relate to navigating the social environment. Areas of the social brain undergo both structural changes and functional reorganization during the second decade of life, possibly reflecting a sensitive period for adapting to one's social environment. The changes in social environment that occur during adolescence might interact with increasing executive functions and heightened social sensitivity to influence a number of adolescent behaviors. We discuss the importance of considering the social environment and social rewards in research on adolescent cognition and behavior. Finally, we speculate about the potential implications of this research for society.

Does age constrain the outcome of all language acquisition equally regardless of whether the language is a first or second one? To test this hypothesis, the English grammatical abilities of deaf and hearing adults who either did or did not have linguistic experience (spoken or signed) during early childhood were investigated with two tasks, timed grammatical judgement and untimed sentence to picture matching. Findings showed that adults who acquired a language in early life performed at near-native levels on a second language regardless of whether they were hearing or deaf or whether the early language was spoken or signed. By contrast, deaf adults who experienced little or no accessible language in early life performed poorly. These results indicate that the onset of language acquisition in early human development dramatically alters the capacity to learn language throughout life, independent of the sensory-motor form of the early experience.

Lenneberg (1967) hypothesized that language could be acquired only within a critical period, extending from early infancy until puberty. In its basic form, the critical period hypothesis need only have consequences for first language acquisition. Nevertheless, it is essential to our understanding of the nature of the hypothesized critical period to determine whether or not it extends as well to second language acquisition. If so, it should be the case that young children are better second language learners than adults and should consequently reach higher levels of final proficiency in the second language. This prediction was tested by comparing the English proficiency attained by 46 native Korean or Chinese speakers who had arrived in the United States between the ages of 3 and 39, and who had lived in the United States between 3 and 26 years by the time of testing. These subjects were tested on a wide variety of structures of English grammar, using a grammaticality judgment task. Both correlational and t-test analyses demonstrated a clear and strong advantage for earlier arrivals over the later arrivals. Test performance was linearly related to age of arrival up to puberty; after puberty, performance was low but highly variable and unrelated to age of arrival. This age effect was shown not to be an inadvertent result of differences in amount of experience with English, motivation, self-consciousness, or American identification. The effect also appeared on every grammatical structure tested, although the structures varied markedly in the degree to which they were well mastered by later learners. The results support the conclusion that a critical period for language acquisition extends its effects to second language acquisition.

A continuing debate in language acquisition research is whether there are critical periods (CPs) in development during which the system is most responsive to environmental input. Recent advances in neurobiology provide a mechanistic explanation of CPs, with the balance between excitatory and inhibitory processes establishing the onset and molecular brakes establishing the offset of windows of plasticity. In this article, we review the literature on human speech perception development within the context of this CP model, highlighting research that reveals the interplay of maturational and experiential influences at key junctures in development and presenting paradigmatic examples testing CP models in human subjects. We conclude with a discussion of how a mechanistic understanding of CP processes changes the nature of the debate: The question no longer is, “Are there CPs?” but rather what processes open them, keep them open, close them, and allow them to be reopened.

This study evaluated the critical period hypothesis for second language (L2) acquisition. The participants were 240 native speakers of Korean who differed according to age of arrival (AOA) in the United States (1 to 23 years), but were all experienced in English (mean length of residence 5 15 years). The native Korean participants’ pronunciation of English was evaluated by having listeners rate their sentences for overall degree of foreign accent; knowledge of English morphosyntax was evaluated using a 144-item grammaticality judgment test. As AOA increased, the foreign accents grew stronger, and the grammaticality judgment test scores decreased steadily. However, unlike the case for the foreign accent ratings, the effect of AOA on the grammaticality judgment test scores became nonsignificant when variables confounded with AOA were controlled. This suggested that the observed decrease in morphosyntax scores was not the result of passing a maturationally defined critical period. Additional analyses showed that the score for sentences testing knowledge of rule based, generalizable aspects of English morphosyntax varied as a function of how much education the Korean participants had received in the United States. The scores for sentences testing lexically based aspects of English morphosyntax, on the other hand, depended on how much the Koreans used English. © 1999 Academic Press

The development of cortical gray matter, white matter (WM) volume, and WM microstructure in adolescence is beginning to be fairly well characterized by structural magnetic resonance imaging (sMRI) and diffusion tensor imaging (DTI) studies. However, these aspects of brain development have rarely been investigated concurrently in the same sample and hence the relations between them are not understood. We delineated the age-related changes in cortical thickness, regional WM volume, and diffusion characteristics and investigated the relationships between these properties of brain development. One hundred and sixty-eight healthy participants aged 8-30 years underwent sMRI and DTI. The results showed regional age-related cortical thinning, WM volume increases, and changes in diffusion parameters. Cortical thickness was the most strongly age-related parameter. All classes of measures showed unique associations with age. The results indicate that cortical thinning in adolescence cannot be explained by WM maturation in underlying regions as measured by volumetry or DTI. Moderate associations between cortical thickness and both volume and diffusion parameters in underlying WM regions were also found, although the relationships were not strong. It is concluded that none of the measures are redundant and that the integration of the 3 will yield a more complete understanding of brain maturation.

This paper provides an introduction to mixed-effects models for the analysis of repeated measurement data with subjects and items as crossed random effects. A worked-out example of how to use recent software for mixed-effects modeling is provided. Simulation studies illustrate the advantages offered by mixed-effects analyses compared to traditional analyses based on quasi-F tests, by-subjects analyses, combined by-subjects and by-items analyses, and random regression. Applications and possibilities across a range of domains of inquiry are discussed.

This study was designed to test the Fundamental Difference Hypothesis (Bley-Vroman, 1988), which states that, whereas children are known to learn language almost completely through (implicit) domain-specific mechanisms, adults have largely lost the ability to learn a language without reflecting on its structure and have to use alternative mechanisms, drawing especially on their problem-solving capacities, to learn a second language. The hypothesis implies that only adults with a high level of verbal analytical ability will reach near-native competence in their second language, but that this ability will not be a significant predictor of success for childhood second language acquisition. A study with 57 adult Hungarian-speaking immigrants confirmed the hypothesis in the sense that very few adult immigrants scored within the range of child arrivals on a grammaticality judgment test, and that the few who did had high levels of verbal analytical ability; this ability was not a significant predictor for childhood arrivals. This study replicates the findings of Johnson and Newport (1989) and provides an explanation for the apparent exceptions in their study. These findings lead to a reconceptualization of the Critical Period Hypothesis: If the scope of this hypothesis is limited to implicit learning mechanisms, then it appears that there may be no exceptions to the age effects that the hypothesis seeks to explain.

Understanding how and when cognitive change occurs over the life span is a prerequisite for understanding normal and abnormal development and aging. Most studies of cognitive change are constrained, however, in their ability to detect subtle, but theoretically informative life-span changes, as they rely on either comparing broad age groups or sparse sampling across the age range. Here, we present convergent evidence from 48,537 online participants and a comprehensive analysis of normative data from standardized IQ and memory tests. Our results reveal considerable heterogeneity in when cognitive abilities peak: Some abilities peak and begin to decline around high school graduation; some abilities plateau in early adulthood, beginning to decline in subjects’ 30s; and still others do not peak until subjects reach their 40s or later. These findings motivate a nuanced theory of maturation and age-related decline, in which multiple, dissociable factors differentially affect different domains of cognition.

This paper identifies several serious problems with the widespread use of ANOVAs for the analysis of categorical outcome variables such as forced-choice variables, question-answer accuracy, choice in production (e.g. in syntactic priming research), et cetera. I show that even after applying the arcsine-square-root transformation to proportional data, ANOVA can yield spurious results. I discuss conceptual issues underlying these problems and alternatives provided by modern statistics. Specifically, I introduce ordinary logit models (i.e. logistic regression), which are well-suited to analyze categorical data and offer many advantages over ANOVA. Unfortunately, ordinary logit models do not include random effect modeling. To address this issue, I describe mixed logit models (Generalized Linear Mixed Models for binomially distributed outcomes, Breslow and Clayton [Breslow, N. E. & Clayton, D. G. (1993). Approximate inference in generalized linear mixed models. Journal of the American Statistical Society 88 (421), 9–25]), which combine the advantages of ordinary logit models with the ability to account for random subject and item effects in one step of analysis. Throughout the paper, I use a psycholinguistic data set to compare the different statistical methods.

Recent studies have shown clear evidence for critical period effects for both first and second language acquisition on a broad range of learned, language-specific grammatical properties. The present studies ask whether and to what degree critical period effects can also be found for universal properties of language considered to be innate. To address this issue, native Chinese speakers who learned English as a second language were tested on the universal principle subjacency as it applies to wh-question formation in English. Subjects arrived in the U.S.A. between the ages of 4 and 38 years. They were immersed in English for a number of years (a minimum of 5) and were adults at the time of testing. Non-native performance on subjacency was found for subjects of all ages of arrival. Performance declined continuously over age of arrival until adulthood, (r = -.63). When immersion occurred as late as adulthood, performance dropped to levels slightly above chance. In all of the analyses performed, subjacency did not differ from language-specific structures in the degree or manner in which it was affected by maturation. These results suggest that whatever the nature of the endowment that allows humans to learn language, it undergoes a very broad deterioration as learners become increasingly mature.

Social cognition provides humans with the necessary skills to understand and interact with one another. One aspect of social cognition, mentalizing, is associated with a network of brain regions often referred to as the 'social brain.' These consist of medial prefrontal cortex [medial Brodmann Area 10 (mBA10)], temporoparietal junction (TPJ), posterior superior temporal sulcus (pSTS) and anterior temporal cortex (ATC). How these specific regions develop structurally across late childhood and adolescence is not well established. This study examined the structural developmental trajectories of social brain regions in the longest ongoing longitudinal neuroimaging study of human brain maturation. Structural trajectories of grey matter volume, cortical thickness and surface area were analyzed using surface-based cortical reconstruction software and mixed modeling in a longitudinal sample of 288 participants (ages 7-30 years, 857 total scans). Grey matter volume and cortical thickness in mBA10, TPJ and pSTS decreased from childhood into the early twenties. The ATC increased in grey matter volume until adolescence and in cortical thickness until early adulthood. Surface area for each region followed a cubic trajectory, peaking in early or pre-adolescence before decreasing into the early twenties. These results are discussed in the context of developmental changes in social cognition across adolescence.

Most research on sensitive periods has focussed on early sensory, motor, and language development, but it has recently been suggested that adolescence might represent a second ‘window of opportunity’ in brain development. Here, we explore three candidate areas of development that are proposed to undergo sensitive periods in adolescence: memory, the effects of social stress, and drug use. We describe rodent studies, neuroimaging, and large-scale behavioural studies in humans that have yielded data that are consistent with heightened neuroplasticity in adolescence. Critically however, concrete evidence for sensitive periods in adolescence is mostly lacking. To provide conclusive evidence, experimental studies are needed that directly manipulate environmental input and compare effects in child, adolescent, and adult groups.

Results from a number of recent studies suggest that nativelike adult second language (L2) learners possess a high degree of language learning aptitude, the positive effects of which may have compensated for the negative effects of a critical period in these learners. According to the same studies, child learners seem to attain a nativelike command of the L2 regardless of high or low aptitude, which has led researchers to conclude that this factor plays no role in early acquisition. The present study investigates the L2 proficiency and language aptitude of 42 near-native L2 speakers of Swedish (i.e., individuals whom actual mother-tongue speakers of Swedish believe are native speakers). The results confirm previous research suggesting that a high degree of language aptitude is required if adult learners are to reach a L2 proficiency that is indistinguishable from that of native speakers. However, in contrast to previous studies, the present results also identify small yet significant aptitude effects in child SLA. Our findings lead us to the conclusions that the rare nativelike adult learners sometimes observed would all turn out to be exceptionally talented language learners with an unusual ability to compensate for maturational effects and, consequently, that their nativelikeness per se does not constitute a reason to reject the critical period hypothesis.

How does the brain manage to store and process multiple languages without encountering massive interference and transfer? Unless we believe that bilinguals live in two totally unconnected cognitive worlds, we would expect far more transfer than actually occurs. However, imaging and lesion studies have not provided consistent evidence for the strict neuronal separation predicted by the theory of modularity. We suggest that emergentist theory offers a promising alternative. It emphasizes the competitive interplay between multiple languages during childhood and by focusing on the dual action of competition and entrenchment, avoids the need to invoke a critical period to account for age of acquisition effects in second-language learning. This view instantiates the motto formulated by Elizabeth Bates that 'modules are made, not born.'

Cortical growth and remodeling continues from birth through youth and adolescence to stable adult levels changing slowly into senescence. There are critical periods of cortical development when specific experiences drive major synaptic rearrangements and learning that only occur during the critical period. For example, visual cortex is characterized by a critical period of plasticity involved in establishing visual acuity. Adolescence is defined by characteristic behaviors that include high levels of risk taking, exploration, novelty and sensation seeking, social interaction and play behaviors. In addition, adolescence is the final period of development of the adult during which talents, reasoning and complex adult behaviors mature. This maturation of behaviors corresponds with periods of marked changes in neurogenesis, cortical synaptic remodeling, neurotransmitter receptors and transporters, as well as major changes in hormones. Frontal cortical development is later in adolescence and likely contributes to refinement of reasoning, goal and priority setting, impulse control and evaluating long and short term rewards. Adolescent humans have high levels of binge drinking and experimentation with other drugs. This review presents findings supporting adolescence as a critical period of cortical development important for establishing life long adult characteristics that are disrupted by alcohol and drug use.