Critical period effects in second language learning: the influence of maturational state on the acquisition of English as a second language

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.     

Language,cognition, and second language grammaticality judgments

In first language research, there appear to be two predominant positions relating metalinguistic awareness to language development. One suggests that since metalinguistic awareness is related to primary language acquisition (comprehension and production), general cognitive processes perform a limited role in metalinguistic awareness. The other suggests that since metalinguistic awareness is more closely related to secondary language acquisition (reading and writing), a greater role is assumed by general cognitive processes. There have been some indirect attempts to study the role of language and cognition with respect to second language grammaticality judgments. There is growing evidence that metalinguistic awareness is a reliable indicator of developing second language competence. Furthermore, it has been shown that language aptitude is significantly related to metalinguistic awareness. The present study was designed to investigate the statistical relationship between second language grammaticality judgments and selected cognitive and linguistic variables. The variables studied were second language proficiency, second language classroom achievement, first language reading competence, language aptitude, nonverbal intelligence, field dependence-independence, and a written grammaticality judgment test tapping the ability to recognize, and correct, deviance. Subjects were college students in advanced English-as-a-second-language classes. Multivariate statistical techniques were used to determine the relative contribution of linguistic and cognitive variables to the individual variation demonstrated by the learners in their ability to detect deviance in English. The results showed that second language proficiency, second language achievement in the classroom, and language aptitude were significant predictors of the subjects' ability to make grammaticality judgments. First language reading competence was significantly related to subjects' ability to correct deviance. These observations are discussed in the light of: (1) the relationship among cognition, language, and metalinguistic awareness, and (2) the role of metalinguistic awareness in second language acquisition and second language learning.     

Age of acquisition: its neural and computational mechanisms

The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects.     

Neural circuitry of the bilingual mental lexicon: Effect of age of second language acquisition

Numerous studies have proposed that changes of the human language faculty caused by neural maturation can explain the substantial differences in ultimate attainment of grammatical competences between first language (L1) acquirers and second language (L2) learners. However, little evidence on the effect of neural maturation on the attainment of lexical knowledge in L2 is available. The present functional magnetic resonance study addresses this question via a cross-linguistic neural adaptation paradigm. Age of acquisition (AoA) of L2 was systematically manipulated. Concrete nouns were repeated across language (e.g., French–German, valise^suitcase–Koffer^suitcase). Whereas early bilinguals (AoA of L2 < 3 years) showed larger repetition enhancement (RE) effects in the left superior temporal gyrus, the bilateral superior frontal gyrus and the right posterior insula, late bilinguals (AoA of L2 > 10 years) showed larger RE effects in the middle portion of the left insula and in the right middle frontal gyrus (MFG). We suggest that, as for grammatical knowledge, the attainment of lexical knowledge in L2 is affected by neural maturation. The present findings lend support to neurocognitive models of bilingual word recognition postulating that, for both early and late bilinguals, the two languages are interconnected at the conceptual level.     

Age of acquisition ratings score better on criterion validity than frequency trajectory or ratings “corrected” for frequency

From the very first studies on the effect of age of acquisition (AoA) on word processing, researchers have validated their AoA ratings by correlating them with other, more objective indices of the age at which children know words. Still, the ratings have been questioned, and alternative measures have been proposed. Two of these are differences in word frequency between language directed at young children and language directed at older children (frequency trajectory) and AoA ratings corrected for word frequency. Surprisingly, the criterion validity of these alternative measures has never been established, partly because one of the validation criteria (the age at which children are able to name pictures) has been questioned. In the present study, four databases are used that aimed to establish the order of English word acquisition, going from the very first words learned to words taught in secondary education. The criteria for word knowledge included word production, multiple-choice questions about the meaning of the words, and teacher judgments about when words should be taught in the school curriculum. For all databases, the frequency trajectory correlated substantially less with the criterion than AoA ratings. For all but one, the same was true for AoA ratings “corrected” for other variables. On the basis of these findings, researchers should be cautious interpreting null effects with the “improved” variables as evidence against a genuine AoA effect.     

Cue strength in second-language processing: An eye-tracking study

This study used eye-tracking and grammaticality judgement measures to examine how second-language (L2) learners process syntactic violations in English. Participants were native Arabic and native Mandarin Chinese speakers studying English as an L2, and monolingual English-speaking controls. The violations involved incorrect word order and differed in two ways predicted to be important by the unified competition model [UCM; MacWhinney, B. (2005). A unified model of language acquisition. In J. F. Kroll & A. M. B. de Groot (Eds.), Handbook of bilingualism: Psycholinguistic approaches (pp. 49–67). Oxford: Oxford University Press.]. First, one violation had more and stronger cues to ungrammaticality than the other. Second, the grammaticality of these word orders varied in Arabic and Mandarin Chinese. Sensitivity to violations was relatively quick overall, across all groups. Sensitivity also was related to the number and strength of cues to ungrammaticality regardless of native language, which is consistent with the general principles of the UCM. However, there was little evidence of cross-language transfer effects in either eye movements or grammaticality judgements.     

Age of acquisition effects in vocabulary learning

Two experiments examined whether the age of acquisition (AoA) of a concept influences the speed at which native English speakers are able to name pictures using a newly acquired second language (L2) vocabulary. In Experiment 1, participants were taught L2 words associated with pictures. In Experiment 2 a second group of participants were taught the same words associated with L1 translations. Following training both groups performed a picture naming task in which they were asked to name pictures using the newly acquired words. Significant AoA effects were observed only in Experiment 1, in that participants were faster at naming pictures representing early acquired relative to late acquired concepts. The results suggest that the AoA of a concept can exert influence over processing which is independent of the AoA of the word form. The results also indicate that different training methods may lead to qualitative differences in the nature of the links formed between words and concepts during the earliest stages of second language learning.     

Age of acquisition in sport: starting early matters

Although the age at which a skill is learned (age of acquisition [AoA]) is one of the most studied predictors of success in domains ranging from language to music, very little work has focused on this factor in sports. In order to uncover how the age at which a skill is learned relates to how athletes cognitively represent that skill, we asked a group of skilled golfers who learned to play golf before (early learners) or after (late learners) the age of 10 to take a series of putts on an indoor putting green. Golfers putted in isolation (single-task condition), while monitoring a stream of words presented over a loudspeaker (dual-task condition), or while being instructed to attend to specific aspects of their golf swing (skill-focused condition). Early and late learners putted equally well in the single-task and dual-task conditions. However, in the skill-focused condition, golfers who learned earlier performed worse than those who learned later. The results are consistent with the notion that AoA influences the manner in which sports, like other domains such as language and music, are represented in memory.     

Critical period effects on universal properties of language: the status of subjacency in the acquisition of a second language.

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.     

Age-of-acquisition effects in native speakers and second-language learners

Two lexical decision experiments were conducted to study the locus of age-of-acquisition (AoA) effects in skilled readers with English or Dutch as their first language. AoA effects have generally been explained in terms of phonological processing. In Experiment 1, Dutch elementary school and secondary school students were presented with words factorially manipulated on surface frequency and AoA). Two main effects and an interaction were found, confirming findings reported for English speakers by Gerhand and Barry (1999). In addition, a language development effect was established: AoA effects decreased with reading age. Elementary school students showed the largest AoA effects. Experiment 2 used two groups of subjects. The first group consisted of Dutch students enrolled in a master's degree program in English. The second group consisted of native speakers of English. All subjects were presented with the experimental set of words used by Gerhand and Barry (1999). British subjects showed the same response pattern as reported by Gerhand and Barry (1999). The question of interest was whether Dutch subjects would show an AoA effect on the English set or not. The answer was affirmative. Dutch subjects produced identical response patterns as the British group, showing only an overall 94-msec latency delay. This result challenges predictions of the phonological completeness hypothesis. Alternative accounts in terms of semantic processing are discussed.     

Age constraints on first versus second language acquisition: evidence for linguistic plasticity and epigenesis

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.     

Support for hybrid models of the age of acquisition of English nouns

Age of acquisition (AoA) is a psycholinguistic construct that refers to the chronological age at which a given word is acquired. Contemporary theories of AoA have focused on lexical acquisition with respect to either the developing phonological or semantic systems. One way of testing the relative dominance of phonological or semantic contributions is through open-source psycholinguistic databases, whereby AoA may be correlated with other variables (e.g., morphology, semantics, phonology). We report two multiple regression analyses conducted on a corpus of English nouns with, respectively, subjective and objective AoA measures as the dependent variables and a combination of 10 predictors, including 2 semantic, 4 phonological, 2 morphological, and 2 lexical. This multivariate combination of predictors accounted for significant proportions of the variance of AoA in both analyses. We argue that this evidence supports hybrid models of language development that integrate multiple levels of processing—from sound to meaning.     

Objective age-of-acquisition (AoA) norms for a set of 230 object names in French: Relationships with psycholinguistic variables,the English data from Morrison et al. (1997), and naming latencies

Picture naming speed is strongly influenced by the age of acquisition (AoA) of words. Most studies of AoA have relied on adults' AoA ratings. However, objective AoA has been found to be a stronger determinant of picture naming latencies. Whereas objective AoA norms for words have been collected for some language communities, no objective AoA measures for words were previously available in French. The study provides objective AoA norms for a set of 230 object names following the procedures used by Morrison, Chappell, and Ellis (1997) to collect objective AoA measures in English. The relationships between objective AoA measures, rated AoA, other variables used in psycholinguistic experiments (name agreement, image agreement, conceptual familiarity, etc.), the English data collected by Morrison et al., and naming latencies are analysed and discussed. In addition, reanalyses of data on picture naming latencies (Bonin, Chalard, Méot, & Fayol, 2002) with the use of objective AoA norms are provided. Stepwise multiple analyses show that objective AoA is a stronger determinant of (spoken and written) naming latencies than rated AoA, whereas objective word frequency is not a reliable independent determinant and does not interact reliably with AoA in any of the analyses.     

The varying effects of age of acquisition

There are a number of theories that suggest that age of acquisition (AoA) effects are not uniform across different tasks. Catling and Johnston (2006a) found greater AoA effects within an object-naming task than in a semantic classification task. They explained these findings by suggesting that AoA effects might accumulate according to how many levels of representation a task necessitates access to. Brysbaert and Ghyselinck (2006) explain the difference in AoA effects by proposing two distinct types of AoA (frequency dependent and frequency independent), the first accounted for by a connectionist-type mechanism and the latter situated at the interface between semantics and word production. Moreover, Moore, Smith-Spark, and Valentine (2004) and Holmes and Ellis (2006) have suggested that there are two loci of AoA effects: at the phonological level and somewhere within the perceptual level of representation. Again, this could account for the varying degrees of AoA effects. This study sets about testing these ideas by assessing the effect size of AoA across a series of different tasks that necessitate access to various levels of representation. Experiments 1–4 demonstrate significant effects of AoA in a novel picture–picture verification task, an object classification task, a picture verification task, and an object-naming task. Experiment 5 showed no effects of initial phoneme on the naming of the critical objects used within Experiments 1–4. The implication of the varying AoA effect sizes found within Experiments 1–4 in relation to explanations of AoA are discussed.     

The distinct contributions of age of acquisition and word frequency in auditory word perception

We report two studies of the distinct effects that a word's age of acquisition (AoA) and frequency have on the mental lexicon. In the first study, a purely statistical analysis, we show that AoA and frequency are related in different ways to the phonological form and imageability of different words. In the second study, three groups of participants (34 seven-year-olds, 30 ten-year-olds, and 17 adults) took part in an auditory lexical decision task, with stimuli varying in AoA, frequency, length, neighbourhood density, and imageability. The principal result is that the influence of these different variables changes as a function of AoA: Neighbourhood density effects are apparent for early and late AoA words, but not for intermediate AoA, whereas imageability effects are apparent for intermediate AoA words but not for early or late AoA. These results are discussed from the perspective that AoA affects a word's representation, but frequency affects processing biases.     

The varying effects of age of acquisition

There are a number of theories that suggest that age of acquisition (AoA) effects are not uniform across different tasks. Catling and Johnston (2006a) found greater AoA effects within an object-naming task than in a semantic classification task. They explained these findings by suggesting that AoA effects might accumulate according to how many levels of representation a task necessitates access to. Brysbaert and Ghyselinck (2006) explain the difference in AoA effects by proposing two distinct types of AoA (frequency dependent and frequency independent), the first accounted for by a connectionist-type mechanism and the latter situated at the interface between semantics and word production. Moreover, Moore, Smith-Spark, and Valentine (2004) and Holmes and Ellis (2006) have suggested that there are two loci of AoA effects: at the phonological level and somewhere within the perceptual level of representation. Again, this could account for the varying degrees of AoA effects. This study sets about testing these ideas by assessing the effect size of AoA across a series of different tasks that necessitate access to various levels of representation. Experiments 1-4 demonstrate significant effects of AoA in a novel picture-picture verification task, an object classification task, a picture verification task, and an object-naming task. Experiment 5 showed no effects of initial phoneme on the naming of the critical objects used within Experiments 1-4. The implication of the varying AoA effect sizes found within Experiments 1-4 in relation to explanations of AoA are discussed.     

Determinants of famous name processing speed: Age of acquisition versus semantic connectedness

The age of acquisition (AoA) and the amount of biographical information known about celebrities have been independently shown to influence the processing of famous people. In this experiment, we investigated the facilitative contribution of both factors to famous name processing. Twenty-four mature adults participated in a familiarity judgement task, in which the names of famous people were grouped orthogonally by AoA and by the number of bits of biographical information known about them (number of facts known; NoFK). Age of acquisition was found to have a significant effect on both reaction time (RT) and accuracy of response, but NoFK did not. The RT data also revealed a significant AoA × NoFK interaction. The amount of information known about a celebrity played a facilitative role in the processing of late-acquired, but not early-acquired, celebrities. Once AoA is controlled, it would appear that the semantic system ceases to have a significant overall influence on the processing of famous people. The pre-eminence of AoA over semantic connectedness is considered in the light of current theories of AoA and how their influence might interact.     

The distinct contributions of age of acquisition and word frequency in auditory word perception

We report two studies of the distinct effects that a word's age of acquisition (AoA) and frequency have on the mental lexicon. In the first study, a purely statistical analysis, we show that AoA and frequency are related in different ways to the phonological form and imageability of different words. In the second study, three groups of participants (34 seven-year-olds, 30 ten-year-olds, and 17 adults) took part in an auditory lexical decision task, with stimuli varying in AoA, frequency, length, neighbourhood density, and imageability. The principal result is that the influence of these different variables changes as a function of AoA: Neighbourhood density effects are apparent for early and late AoA words, but not for intermediate AoA, whereas imageability effects are apparent for intermediate AoA words but not for early or late AoA. These results are discussed from the perspective that AoA affects a word's representation, but frequency affects processing biases.     

Concurrent language and motor performance in bilinguals: a test of the age of acquisition hypothesis.

The objective of the present study was to test the hypothesis that the age at which a second language is acquired influences the pattern of cerebral lateralization associated with that language. Subjects who differed in terms of the age at which they had acquired their second language (English or French) were tested on a concurrent task paradigm involving motor and language performance. Hemispheric processing was inferred from the pattern of lateralized and generalized interference between the tasks. No support was found for the age-of-acquisition hypothesis. Instead, the data indicated a language-specific effect. Regardless of age of acquisition and of whether the first language was English or French, bilingual subjects showed lateralized interference effects consistent with left-hemisphere processing when reading in English and translating from French into English, but no lateralized interference when reading in French and translating from English into French. Whether this effect reflects characteristics of the two languages or the influence of social factors in subject-experimenter interaction is considered.     

Age of acquisition and word frequency in written picture naming

This study investigates age of acquisition (AoA) and word frequency effects in both spoken and written picture naming. In the first two experiments, reliable AoA effects on object naming speed, with objective word frequency controlled for, were found in both spoken (Experiment 1) and written picture naming (Experiment 2). In contrast, no reliable objective word frequency effects were observed on naming speed, with AoA controlled for, in either spoken (Experiment 3) or written (Experiment 4) picture naming. The implications of the findings for written picture naming are briefly discussed.