Critical Period Hypothesis
Encyclopedia
The critical period hypothesis is the subject of a long-standing debate in linguistics
and language acquisition
over the extent to which the ability to acquire language
is biologically linked to age. The hypothesis claims that there is an ideal 'window' of time to acquire language in a linguistically rich environment, after which further language acquisition becomes much more difficult and effortful.
The critical period hypothesis states that the first few years of life is the crucial time in which an individual can acquire a first language
if presented with adequate stimuli. If language input doesn't occur until after this time, the individual will never achieve a full command of language—especially grammatical systems
.
The evidence for such a period is limited, and support stems largely from theoretical arguments and analogies to other critical periods in biology such as visual development
, but nonetheless is widely accepted. The nature of this phenomenon, however, has been one of the most fiercely debated issues in psycholinguistics
and cognitive science
in general for decades. Some writers have suggested a "sensitive" or "optimal" period rather than a critical one; others dispute the causes (physical maturation, cognitive factors). The duration of the period also varies greatly in different accounts.
In second language acquisition
, the strongest evidence for the critical period hypothesis is in the study of accent
, where most older learners do not reach a native-like level. However, under certain conditions, native-like accent has been observed, suggesting that accent is affected by multiple factors, such as identity
and motivation, rather than a critical period biological constraint (Moyer, 1999; Bongaerts et al., 1995; Young-Scholten, 2002).
and co-author Lamar Roberts in a 1959 paper Speech and Brain Mechanisms, and was popularised by Eric Lenneberg
in 1967 with Biological Foundations of Language.
Lenneberg states that there are maturational constraints on the time a first language can be acquired. First language acquisition relies on neuroplasticity
. If language acquisition does not occur by puberty, some aspects of language can be learnt but full mastery cannot be achieved. This was called the "critical period hypothesis."
An interesting example of this is the case of Genie
. A thirteen-year-old victim of lifelong child abuse
, Genie had been kept strapped to a potty chair and wearing diapers. She appeared to be entirely without language. Her father had judged her retarded at birth and had chosen to isolate her, and so she had remained until her discovery.
It was an ideal opportunity to test the theory that a nurturing environment could somehow make up for a total lack of language past the age of 12. She was unable to acquire language completely, although the degree to which she acquired language is disputed.
Detractors of the "Critical Period Hypothesis" point out that in this example and others like it (see Feral children), the child is hardly growing up in a nurturing environment, and that the lack of language acquisition in later life may be due to the results of a generally abusive environment rather than being specifically due to a lack of exposure to language.
Recently, it has been suggested that if a critical period does exist, it may be due at least partially to the delayed development of the prefrontal cortex
in human children. Researchers have suggested that delayed development of the prefrontal cortex
and a concomitant delay in the development of cognitive control may facilitate convention learning, allowing young children to learn language far more easily than cognitively mature adults and older children. This pattern of prefrontal development is unique to humans among similar mammalian (and primate) species, and may explain why humans—and not chimpanzees—are so adept at learning language.
(SLA), although this is much less widely accepted. Certainly, older learners of a second language
rarely achieve the native-like fluency that younger learners display, despite often progressing faster than children in the initial stages. David Singleton states that in learning a second language, "younger = better in the long run," but points out that there are many exceptions, noting that five percent of adult bilinguals master a second language even though they begin learning it when they are well into adulthood—long after any critical period has presumably come to a close.
While the window for learning a second language never completely closes, certain linguistic aspects appear to be more affected by the age of the learner than others. For example, adult second-language learners nearly always retain an immediately identifiable foreign accent, including some who display perfect grammar (Oyama 1976). Some writers have suggested a younger critical age for learning phonology than for syntax. Singleton (1995) reports that there is no critical period for learning vocabulary in a second language. Robertson (2002)] observed that factors other than age may be even more significant in successful second language learning, such as personal motivation, anxiety, input and output skills, settings and time commitment.
On reviewing the published material, Bialystok and Hakuta (1994) conclude that second-language learning is not necessarily subject to biological critical periods, but "on average, there is a continuous decline in ability [to learn] with age."
’ (CP) ideas. A CP was popularised by Eric Lenneberg
in 1967 for L1 acquisition, but considerable interest now surrounds age effects on second language acquisition (SLA). SLA theories explain learning processes and suggest causal factors for a possible CP for SLA, mainly attempting to explain apparent differences in language aptitudes of children and adults by distinct learning routes, and clarifying them through psychological mechanisms. Research explores these ideas and hypotheses, but results are varied: some demonstrate pre-pubescent children acquire language easily, and some that older learners have the advantage, whilst others focus on existence of a CP for SLA. Recent studies (e.g. Mayberry and Lock, 2003) have recognised certain aspects of SLA may be affected by age, whilst others remain intact. The objective of this study is to investigate whether capacity for vocabulary acquisition decreases with age.
Other work has challenged the biological approach; Krashen (1975) re-analysed clinical data used as evidence and concluded cerebral specialisation occurs much earlier than Lenneberg calculated. Therefore, if a CP exists, it does not coincide with lateralisation. Despite concerns with Lenneberg’s original evidence and the dissociation of lateralisation from the language CP idea, however, the concept of a CP remains a viable hypothesis, which later work has better explained and substantiated.
, who was deprived of social interaction from birth until discovered aged thirteen (post-pubescent). She was completely without language, and after seven years of rehabilitation still lacked linguistic competence. Another case is ‘Isabelle’, who was incarcerated with her deaf-mute brother until the age of six and a half (pre-pubescent). She also had no language skills, but, unlike Genie, quickly acquired normal language abilities through systematic specialist training.
Such studies are however problematic; isolation can result in general retardation and emotional disturbances, which may confound conclusions drawn about language abilities. Studies of deaf children learning American Sign Language (ASL) have fewer methodological weaknesses. Newport and Supalla (1987) studied ASL acquisition in deaf children differing in age of exposure; few were exposed to ASL from birth, most of them first learned it at school.
Results showed a linear decline in performance with increasing age of exposure; those exposed to ASL from birth performed best, and ‘late learners’ worst, on all production and comprehension tests. Their study thus provides direct evidence for language learning ability decreasing with age, but it does not add to Lennerberg’s CP hypothesis as even the oldest children, the ‘late learners’, were exposed to ASL by age four, and had therefore not reached puberty, the proposed end of the CP. In addition, the declines were shown to be linear, with no sudden ‘drop off’ of ability at a certain age, as would be predicted by a strong CP hypothesis. That the children performed significantly worse, however, suggests the CP may end earlier than originally postulated.
. Skinner
(1957) details how operant conditioning
forms connections with the environment through interaction and, alongside O. Hobart Mowrer (1960), applies the ideas to language acquisition. Mowrer hypothesises that languages are acquired through rewarded imitation of ‘language models’; the model must have an emotional link to the learner (e.g. parent, spouse), as imitation then brings pleasant feelings which function as positive reinforcement. Because new connections between behaviour and the environment are formed and reformed throughout life, it is possible to gain new skills, including language(s), at any age.
To accommodate observed language learning differences between children and adults, Felix (1985) describes that children, whose brains create countless new connections daily, may handle the language learning process more effectively than do adults. This assumption, however, remains untested and is not a reliable explanation for children’s aptitude for L2 learning. Problematic of the behaviourist approach is its assumption that all learning, verbal and non-verbal, occurs through the same processes. A more general problem is that, as Pinker (1995) notes, almost every sentence anybody voices is an original combination of words, never previously uttered, therefore a language cannot consist only of word combinations learned through repetition and conditioning; the brain must contain innate means of creating endless amounts of grammatical sentences from a limited vocabulary. This is precisely what Chomsky (1965) argues with his proposition of a Universal Grammar
(UG).
’ (LAD) in the brain. These principles denote restricted possibilities for variation within the language, and enable learners to construct a grammar out of ‘raw input’ collected from the environment. Input alone cannot explain language acquisition because it is degenerated by characteristic features such as stutters, and lacks corrections from which learners discover incorrect variations.
Singleton and Newport (2004) demonstrate the function of UG in their study of ‘Simon’. Simon learned ASL as his L1 from parents who had learned it as an L2 after puberty and provided him with imperfect models. Results showed Simon learned normal and logical rules and was able to construct an organised linguistic system, despite being exposed to inconsistent input. Chomsky developed UG to explain L1 acquisition data, but maintains it also applies to L2 learners who achieve near-native fluency not attributable solely to input and interaction (Chomsky, 1965).
Although it does not describe an optimal age for SLA, the theory implies that younger children can learn languages more easily than older learners, as adults must reactivate principles developed during L1 learning and forge an SLA path: children can learn several languages simultaneously as long as the principles are still active and they are exposed to sufficient language samples (Pinker, 1995). The parents of Singleton and Newport’s (2004) patient also had linguistic abilities in line with these age-related predictions; they learned ASL after puberty and never reached complete fluency.
(1999) investigates how cerebral circuits used to handling one language adapt for the efficient storage of two or more. He reports observations of cerebral activation when reading and translating two languages. They found the most activated brain areas during the tasks were not those generally associated with language, but rather those related to mapping orthography
to phonology
. They conclude that the left temporal lobe is the physical base of L1, but the L2 is ‘stored’ elsewhere, thus explaining cases of bilingual aphasia where one language remains intact. They maintain that only languages learned simultaneously from birth are represented, and cause activity, in the left hemisphere: any L2 learned later is stored separately (possibly in the right hemisphere), and rarely activates the left temporal lobe.
This suggests that L2 may be qualitatively different from L1 due to its dissociation from the ‘normal’ language brain regions, thus the extrapolation of L1 studies and theories to SLA is placed in question. A further disadvantage of UG is that supporting empirical data are taken from a limited sample of syntactic phenomena: a general theory of language acquisition should cover a larger range of phenomena. Despite these problems, several other theorists have based their own models of language learning on it; amongst others Felix’ (1985) ‘competing cognitive systems’ idea. These ideas are supported by empirical evidence, which consequently supports Chomsky’s ideas. Due to this support and its descriptive and explanatory strength, many theorists regard UG as the best explanation of language, and particularly grammar, acquisition.
posited by Chomsky and his followers still accessible to learners of a second language? Research suggests that it becomes inaccessible at a certain age (see Critical Period Hypothesis
), and learners increasingly depended on explicit teaching (see pedagogical effects above, and age below). In other words, although all of language may be governed by UG, older learners might have great difficulty in gaining access to the target language's underlying rules from positive input alone.
(1926) is one psychologist reluctant to ascribe specific innate linguistic abilities to children: he considers the brain a homogeneous computational system, with language acquisition being one part of general learning. He agrees this development may be innate, but claims there is no specific language acquisition module in the brain. Instead, he suggests external influences and social interaction trigger language acquisition: information collected from these sources constructs symbolic and functional schemata (thought or behaviour patterns). According to Piaget, cognitive development and language acquisition are life-long active processes that constantly update and re-organise schemata. He proposes children develop L1 as they build a sense of identity in reference to the environment, and describes phases of general cognitive development, with processes and patterns changing systematically with age. Piaget assumes language acquisition is part of this complex cognitive development, and that these developmental phases are the basis for an optimal period for language acquisition in childhood. Interactionist approaches derived from Piaget’s ideas supports his theory. Some studies (e.g. Newport and Supalla, 1987) show that, rather than abrupt changes in SLA ability after puberty, language ability declines with age, coinciding with declines in other cognitive abilities, thus supporting Piaget.
(1975) also criticises this theory, neither he nor Felix discredit the importance of age for second language acquisition. Krashen (1975), and later Felix (1985), proposed theories for the close of the CP for L2 at puberty, based on Piaget’s cognitive stage of formal operations beginning at puberty, as the ‘ability of the formal operational thinker to construct abstract hypotheses to explain phenomena’ inhibits the individual’s natural ability for language learning.
The term "language acquisition
" became commonly used after Stephen Krashen
contrasted it with formal and non-constructive "learning." Today, most scholars use "language learning" and "language acquisition" interchangeably, unless they are directly addressing Krashen's work. However, "second language acquisition" or "SLA" has become established as the preferred term for this academic discipline.
Though SLA is often viewed as part of applied linguistics
, it is typically concerned with the language system and learning processes themselves, whereas applied linguistics may focus more on the experiences of the learner, particularly in the classroom. Additionally, SLA has mostly examined naturalistic acquisition, where learners acquire a language with little formal training or teaching.
Empirical research has attempted to account for variables detailed by SLA theories and provide an insight into L2 learning processes, which can be applied in educational environments. Recent SLA investigations have followed two main directions: one focuses on pairings of L1 and L2 that render L2 acquisition particularly difficult, and the other investigates certain aspects of language that may be maturationally constrained. Flege, Mackay and Piske (2002) looked at bilingual dominance to evaluate two explanations of L2 performance differences between bilinguals and monolingual-L2 speakers, i.e. a maturationally defined CP or interlingual interference.
-English bilinguals, and found the early bilinguals were English (L2) dominant and the late bilinguals Italian (L1) dominant. Further analysis showed that dominant Italian bilinguals had detectable foreign accents when speaking English, but early bilinguals (English dominant) had no accents in either language. This suggests that, though interlingual interference effects are not inevitable, their emergence, and bilingual dominance, may be related to a CP.
Sebastián-Gallés, Echeverría and Bosch (2005) also studied bilinguals and highlight the importance of early language exposure. They looked at vocabulary processing and representation in Spanish
-Catalan
bilinguals exposed to both languages simultaneously from birth in comparison to those who had learned L2 later and were either Spanish- or Catalan-dominant. Findings showed ‘from birth bilinguals’ had significantly more difficulty distinguishing Catalan words from non-words differing in specific vowels than Catalan-dominants did (measured by reaction time).
These difficulties are attributed to a phase around age eight months where bilingual infants are insensitive to vowel contrasts, despite the language they hear most. This affects how words are later represented in their lexicon
s, highlighting this as a decisive period in language acquisition and showing that initial language exposure shapes linguistic processing for life. Sebastián-Gallés et al. (2005) also indicate the significance of phonology for L2 learning; they believe learning an L2 once the L1 phonology is already internalised can reduce individuals’ abilities to distinguish new sounds that appear in the L2.
verb systems and syntax. However, comparing early immersion students (average age 6.917 years) with age-matched native speakers identified common problem areas, including third person plurals and polite ‘vous
’ forms. This suggests grammar (in L1 or L2) is generally acquired later, possibly because it requires abstract cognition and reasoning (B. Harley, 1986).
B. Harley also measured eventual attainment and found the two age groups made similar mistakes in syntax and lexical selection, often confusing French with the L1. The general conclusion from these investigations is that different aged learners acquire the various aspects of language with varying difficulty. Some variation in grammatical performance is attributed to maturation (discussed in B. Harley, 1986), however, all participants began immersion programs before puberty and so were too young for a strong critical period hypothesis to be directly tested.
This corresponds to Noam Chomsky
’s UG theory, which states that while language acquisition principles are still active, it is easy to learn a language, and the principles developed through L1 acquisition are vital for learning an L2.
Scherag, Demuth, Rösler, Neville and Röder (2004) also suggest learning some syntactic processing functions and lexical access may be limited by maturation, whereas semantic functions are relatively unaffected by age. They studied the effect of late SLA on speech comprehension by German
immigrants to the U.S.A. and American immigrants to Germany. They found that native-English speakers who learned German as adults were disadvantaged on certain grammatical tasks but performed at near-native levels on lexical tasks. These findings are consistent with work by Hahne (2001, cited in Scherag et al., 2004).
-English bilinguals who had been exposed to English after puberty, learned vocabulary to a higher competence level than syntactic aspects of language. They do, however, report that the judgment accuracies in detecting semantic anomalies were altered in subjects who were exposed to English after sixteen years of age, but were affected to a lesser degree than were grammatical aspects of language. It has been speculated (Neville and Bavelier, 2001, and Scherag et al., 2004) that semantic aspects of language are founded on associative learning mechanisms, which allow life-long learning, whereas syntactical aspects are based on computational mechanisms, which can only be constructed during certain age periods. Consequently, it is reasoned, semantic functions are easier to access during comprehension of an L2 and therefore dominate the process: if these are ambiguous, understanding of syntactic information is not facilitated. These suppositions would help explain the results of Scherag et al.’s (2004) study.
According to Linda M. Espinosa, especially in the United States the number of children growing up with a home language that is not English but Spanish is constantly increasing. Therefore these children have to learn the English language before kindergarten as a second language. It is better to dispose young children to maintain both, their home language and their second language. Cultivating his home language, the child creates his own cultural identity and becomes aware of his roots. This fact leads to the question whether having the ability to speak two languages helps or harms young children. Research shows that the acquisition of a second language in early childhood confers several advantages, especially a greater awareness of linguistic structures. Furthermore it is advantageous for young children to grow up bilingually because they do not need to be taught systematically but learn languages intuitively. How fast a child can learn a language depends on several personal factors, such as interest and motivation, and its learning environment. Communication should be facilitated rather than a child should be forced to learn a language with strict rules. Education in early childhood can lead to an effective educational achievement for children from various cultural environments.
Another aspect that is worth considering is that bilingual children are often doing code switching which does not mean that the child is not able to separate the languages. The reason for code switching is the child's lack of vocabulary in a certain situation. The acquisition of a second language in early childhood broadens the children's minds and enriches them more than it harms them. Thus they are not only able to speak two languages in spite of being very young but they also acquire knowledge about the different cultures and environments. It is possible that one language can dominate. This depends on how much time is spent on learning each language.
1. Language is an evolutionary adaptation that is naturally selected for.
2. Any given individual’s language can be quantified or measured.
3. Various aspects of maturation and development are under genetic control, which would extend to determine the timing for critical periods for certain capacities (i.e. polygenic inheritance).
According to Hurford’s evolutionary model, language acquisition is an adaptation that has survival value for humans, and that knowing a language correlated positively with an individual’s reproductive advantage. This finding is in line with views of other researchers such as Chomsky
(1982) and Pinker & Bloom (1990). For example, Steven Pinker
and Paul Bloom argue that due to the fact that language is a complex design that serves a specific function that cannot be replaced by any other existing capacity, the trait of language acquisition can be attributed to natural selection.
However, while arguing that language itself is adaptive and “did not ‘just happen’” (p.172), Hurford suggests that the critical period is not an adaptation, but rather a constraint on language that emerged due to a lack of selection pressures that reinforce acquiring more than one language. In other words, Hurford explains the existence of a critical period with genetic drift
, the idea that when there are no selection pressures on multiple alleles acting on the same trait, one of the alleles will gradually diminish through evolution. Because the simulation reveals no evolutionary advantage of acquiring more than one language, Hurford suggests that the critical period evolved simply as a result of a lack of selection pressure.
1. Language ability correlates with an individual’s reproductive fitness
2. The ability to learn language is inherited
3. There are costs to learning a language
Their model consists of a population with constant size, where language ability is a predictor of reproductive fitness. The learning mechanism in their model is based on Chomsky’s (1980, 1993) language acquisition device
(LAD) and the notion of universal grammar
. The results of their model show that the critical period for language acquisition is an “evolutionarily stable strategy
(ESS)” (Komarova & Nowak, 2001, p. 1190). They suggest that this ESS is due to two competing selection pressures. First, if the period for learning is short, language does not develop as well, and thus decreases the evolutionary fitness of the individual. Alternatively, if the period for learning language is long, it becomes too costly to the extent that it reduces reproductive opportunity for the individual, and therefore limits reproductive fitness. Therefore, the critical period is an adaptive mechanism that keeps these pressures at equilibrium, and aims at optimal reproductive success for the individual.
Linguistics
Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....
and language acquisition
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...
over the extent to which the ability to acquire language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
is biologically linked to age. The hypothesis claims that there is an ideal 'window' of time to acquire language in a linguistically rich environment, after which further language acquisition becomes much more difficult and effortful.
The critical period hypothesis states that the first few years of life is the crucial time in which an individual can acquire a first language
First language
A first language is the language a person has learned from birth or within the critical period, or that a person speaks the best and so is often the basis for sociolinguistic identity...
if presented with adequate stimuli. If language input doesn't occur until after this time, the individual will never achieve a full command of language—especially grammatical systems
Grammar
In linguistics, grammar is the set of structural rules that govern the composition of clauses, phrases, and words in any given natural language. The term refers also to the study of such rules, and this field includes morphology, syntax, and phonology, often complemented by phonetics, semantics,...
.
The evidence for such a period is limited, and support stems largely from theoretical arguments and analogies to other critical periods in biology such as visual development
Visual system
The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...
, but nonetheless is widely accepted. The nature of this phenomenon, however, has been one of the most fiercely debated issues in psycholinguistics
Psycholinguistics
Psycholinguistics or psychology of language is the study of the psychological and neurobiological factors that enable humans to acquire, use, comprehend and produce language. Initial forays into psycholinguistics were largely philosophical ventures, due mainly to a lack of cohesive data on how the...
and cognitive science
Cognitive science
Cognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
in general for decades. Some writers have suggested a "sensitive" or "optimal" period rather than a critical one; others dispute the causes (physical maturation, cognitive factors). The duration of the period also varies greatly in different accounts.
In second language acquisition
Second language acquisition
Second-language acquisition or second-language learning is the process by which people learn a second language. Second-language acquisition is also the name of the scientific discipline devoted to studying that process...
, the strongest evidence for the critical period hypothesis is in the study of accent
Accent (linguistics)
In linguistics, an accent is a manner of pronunciation peculiar to a particular individual, location, or nation.An accent may identify the locality in which its speakers reside , the socio-economic status of its speakers, their ethnicity, their caste or social class, their first language In...
, where most older learners do not reach a native-like level. However, under certain conditions, native-like accent has been observed, suggesting that accent is affected by multiple factors, such as identity
Identity (social science)
Identity is a term used to describe a person's conception and expression of their individuality or group affiliations . The term is used more specifically in psychology and sociology, and is given a great deal of attention in social psychology...
and motivation, rather than a critical period biological constraint (Moyer, 1999; Bongaerts et al., 1995; Young-Scholten, 2002).
History
The critical period hypothesis was first proposed by Montreal neurologist Wilder PenfieldWilder Penfield
Wilder Graves Penfield, OM, CC, CMG, FRS was an American born Canadian neurosurgeon. During his life he was called "the greatest living Canadian"...
and co-author Lamar Roberts in a 1959 paper Speech and Brain Mechanisms, and was popularised by Eric Lenneberg
Eric Lenneberg
Eric Heinz Lenneberg was a linguist and neurologist who pioneered ideas on language acquisition and cognitive psychology, particularly in terms of the concept of innateness....
in 1967 with Biological Foundations of Language.
Lenneberg states that there are maturational constraints on the time a first language can be acquired. First language acquisition relies on neuroplasticity
Neuroplasticity
Neuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...
. If language acquisition does not occur by puberty, some aspects of language can be learnt but full mastery cannot be achieved. This was called the "critical period hypothesis."
An interesting example of this is the case of Genie
Genie (feral child)
Genie is the pseudonym for a feral child who spent nearly all of the first thirteen years of her life locked inside a bedroom strapped to a potty chair. She was a victim of one of the most severe cases of social isolation ever documented...
. A thirteen-year-old victim of lifelong child abuse
Child abuse
Child abuse is the physical, sexual, emotional mistreatment, or neglect of a child. In the United States, the Centers for Disease Control and Prevention and the Department of Children And Families define child maltreatment as any act or series of acts of commission or omission by a parent or...
, Genie had been kept strapped to a potty chair and wearing diapers. She appeared to be entirely without language. Her father had judged her retarded at birth and had chosen to isolate her, and so she had remained until her discovery.
It was an ideal opportunity to test the theory that a nurturing environment could somehow make up for a total lack of language past the age of 12. She was unable to acquire language completely, although the degree to which she acquired language is disputed.
Detractors of the "Critical Period Hypothesis" point out that in this example and others like it (see Feral children), the child is hardly growing up in a nurturing environment, and that the lack of language acquisition in later life may be due to the results of a generally abusive environment rather than being specifically due to a lack of exposure to language.
Recently, it has been suggested that if a critical period does exist, it may be due at least partially to the delayed development of the prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
in human children. Researchers have suggested that delayed development of the prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
and a concomitant delay in the development of cognitive control may facilitate convention learning, allowing young children to learn language far more easily than cognitively mature adults and older children. This pattern of prefrontal development is unique to humans among similar mammalian (and primate) species, and may explain why humans—and not chimpanzees—are so adept at learning language.
Second language acquisition
The theory has often been extended to a critical period for second language acquisitionSecond language acquisition
Second-language acquisition or second-language learning is the process by which people learn a second language. Second-language acquisition is also the name of the scientific discipline devoted to studying that process...
(SLA), although this is much less widely accepted. Certainly, older learners of a second language
Second language
A second language or L2 is any language learned after the first language or mother tongue. Some languages, often called auxiliary languages, are used primarily as second languages or lingua francas ....
rarely achieve the native-like fluency that younger learners display, despite often progressing faster than children in the initial stages. David Singleton states that in learning a second language, "younger = better in the long run," but points out that there are many exceptions, noting that five percent of adult bilinguals master a second language even though they begin learning it when they are well into adulthood—long after any critical period has presumably come to a close.
While the window for learning a second language never completely closes, certain linguistic aspects appear to be more affected by the age of the learner than others. For example, adult second-language learners nearly always retain an immediately identifiable foreign accent, including some who display perfect grammar (Oyama 1976). Some writers have suggested a younger critical age for learning phonology than for syntax. Singleton (1995) reports that there is no critical period for learning vocabulary in a second language. Robertson (2002)] observed that factors other than age may be even more significant in successful second language learning, such as personal motivation, anxiety, input and output skills, settings and time commitment.
On reviewing the published material, Bialystok and Hakuta (1994) conclude that second-language learning is not necessarily subject to biological critical periods, but "on average, there is a continuous decline in ability [to learn] with age."
Experimental and observational studies
How children acquire native language (L1) and the relevance of this to foreign language (L2) learning has long been debated. Although evidence for L2 learning ability declining with age is controversial, a common notion is that children learn L2s easily, whilst older learners rarely achieve fluency. This assumption stems from ‘critical periodCritical period
This article is about a critical period in an organism's or person's development. See also America's Critical Period.In general, a critical period is a limited time in which an event can occur, usually to result in some kind of transformation...
’ (CP) ideas. A CP was popularised by Eric Lenneberg
Eric Lenneberg
Eric Heinz Lenneberg was a linguist and neurologist who pioneered ideas on language acquisition and cognitive psychology, particularly in terms of the concept of innateness....
in 1967 for L1 acquisition, but considerable interest now surrounds age effects on second language acquisition (SLA). SLA theories explain learning processes and suggest causal factors for a possible CP for SLA, mainly attempting to explain apparent differences in language aptitudes of children and adults by distinct learning routes, and clarifying them through psychological mechanisms. Research explores these ideas and hypotheses, but results are varied: some demonstrate pre-pubescent children acquire language easily, and some that older learners have the advantage, whilst others focus on existence of a CP for SLA. Recent studies (e.g. Mayberry and Lock, 2003) have recognised certain aspects of SLA may be affected by age, whilst others remain intact. The objective of this study is to investigate whether capacity for vocabulary acquisition decreases with age.
Other work has challenged the biological approach; Krashen (1975) re-analysed clinical data used as evidence and concluded cerebral specialisation occurs much earlier than Lenneberg calculated. Therefore, if a CP exists, it does not coincide with lateralisation. Despite concerns with Lenneberg’s original evidence and the dissociation of lateralisation from the language CP idea, however, the concept of a CP remains a viable hypothesis, which later work has better explained and substantiated.
Effects of aging
A review of SLA theories and their explanations for age-related differences is necessary before considering empirical studies. The most reductionist theories are those of Penfield and Roberts (1959) and Lenneberg (1967), which stem from L1 and brain damage studies; children who suffer impairment before puberty typically recover and (re-)develop normal language, whereas adults rarely recover fully, and often do not regain verbal abilities beyond the point reached five months after impairment. Both theories agree that children have a neurological advantage in learning languages, and that puberty correlates with a turning point in ability. They assert that language acquisition occurs primarily, possibly exclusively, during childhood as the brain loses plasticity after a certain age. It then becomes rigid and fixed, and loses the ability for adaptation and reorganisation, rendering language (re-)learning difficult. Penfield and Roberts (1959) claim children under nine can learn up to three languages: early exposure to different languages activates a reflex in the brain allowing them to switch between languages without confusion or translation into L1 (Penfield, 1964). Lenneberg (1967) asserts that if no language is learned by puberty, it cannot be learned in a normal, functional sense. He also supports Penfield and Roberts’ (1959) proposal of neurological mechanisms responsible for maturational change in language learning abilities. This, Lenneberg maintains, coincides with brain lateralisation and left-hemispherical specialisation for language around age thirteen: infants’ motor and linguistic skills develop simultaneously, but by age thirteen the cerebral hemispheres’ functions separate and become set, making language acquisition extremely difficult (Lenneberg, 1967).Deaf and feral children
Cases of deaf and feral children provide evidence for a biologically determined CP for L1. Feral children are those not exposed to language in infancy/childhood due to being brought up in the wild, in isolation and/or confinement. A classic example is 'Genie'Genie (feral child)
Genie is the pseudonym for a feral child who spent nearly all of the first thirteen years of her life locked inside a bedroom strapped to a potty chair. She was a victim of one of the most severe cases of social isolation ever documented...
, who was deprived of social interaction from birth until discovered aged thirteen (post-pubescent). She was completely without language, and after seven years of rehabilitation still lacked linguistic competence. Another case is ‘Isabelle’, who was incarcerated with her deaf-mute brother until the age of six and a half (pre-pubescent). She also had no language skills, but, unlike Genie, quickly acquired normal language abilities through systematic specialist training.
Such studies are however problematic; isolation can result in general retardation and emotional disturbances, which may confound conclusions drawn about language abilities. Studies of deaf children learning American Sign Language (ASL) have fewer methodological weaknesses. Newport and Supalla (1987) studied ASL acquisition in deaf children differing in age of exposure; few were exposed to ASL from birth, most of them first learned it at school.
Results showed a linear decline in performance with increasing age of exposure; those exposed to ASL from birth performed best, and ‘late learners’ worst, on all production and comprehension tests. Their study thus provides direct evidence for language learning ability decreasing with age, but it does not add to Lennerberg’s CP hypothesis as even the oldest children, the ‘late learners’, were exposed to ASL by age four, and had therefore not reached puberty, the proposed end of the CP. In addition, the declines were shown to be linear, with no sudden ‘drop off’ of ability at a certain age, as would be predicted by a strong CP hypothesis. That the children performed significantly worse, however, suggests the CP may end earlier than originally postulated.
Behavioural approaches
Contrary to biological views, behavioural approaches assert that languages are learned as any other behaviour, through conditioningOperant conditioning
Operant conditioning is a form of psychological learning during which an individual modifies the occurrence and form of its own behavior due to the association of the behavior with a stimulus...
. Skinner
B. F. Skinner
Burrhus Frederic Skinner was an American behaviorist, author, inventor, baseball enthusiast, social philosopher and poet...
(1957) details how operant conditioning
Operant conditioning
Operant conditioning is a form of psychological learning during which an individual modifies the occurrence and form of its own behavior due to the association of the behavior with a stimulus...
forms connections with the environment through interaction and, alongside O. Hobart Mowrer (1960), applies the ideas to language acquisition. Mowrer hypothesises that languages are acquired through rewarded imitation of ‘language models’; the model must have an emotional link to the learner (e.g. parent, spouse), as imitation then brings pleasant feelings which function as positive reinforcement. Because new connections between behaviour and the environment are formed and reformed throughout life, it is possible to gain new skills, including language(s), at any age.
To accommodate observed language learning differences between children and adults, Felix (1985) describes that children, whose brains create countless new connections daily, may handle the language learning process more effectively than do adults. This assumption, however, remains untested and is not a reliable explanation for children’s aptitude for L2 learning. Problematic of the behaviourist approach is its assumption that all learning, verbal and non-verbal, occurs through the same processes. A more general problem is that, as Pinker (1995) notes, almost every sentence anybody voices is an original combination of words, never previously uttered, therefore a language cannot consist only of word combinations learned through repetition and conditioning; the brain must contain innate means of creating endless amounts of grammatical sentences from a limited vocabulary. This is precisely what Chomsky (1965) argues with his proposition of a Universal Grammar
Universal grammar
Universal grammar is a theory in linguistics that suggests that there are properties that all possible natural human languages have.Usually credited to Noam Chomsky, the theory suggests that some rules of grammar are hard-wired into the brain, and manifest themselves without being taught...
(UG).
Universal Grammar
Chomsky (1965) asserts that environmental factors must be relatively unimportant for language emergence, as so many different factors surround children acquiring L1. Instead, Chomsky claims language learners possess innate principles building a ‘language acquisition deviceLanguage acquisition device
The Language Acquisition Device is a postulated "organ" of the brain that is supposed to function as a congenital device for learning symbolic language . First proposed by Noam Chomsky, the LAD concept is an instinctive mental capacity which enables an infant to acquire and produce language. It is...
’ (LAD) in the brain. These principles denote restricted possibilities for variation within the language, and enable learners to construct a grammar out of ‘raw input’ collected from the environment. Input alone cannot explain language acquisition because it is degenerated by characteristic features such as stutters, and lacks corrections from which learners discover incorrect variations.
Singleton and Newport (2004) demonstrate the function of UG in their study of ‘Simon’. Simon learned ASL as his L1 from parents who had learned it as an L2 after puberty and provided him with imperfect models. Results showed Simon learned normal and logical rules and was able to construct an organised linguistic system, despite being exposed to inconsistent input. Chomsky developed UG to explain L1 acquisition data, but maintains it also applies to L2 learners who achieve near-native fluency not attributable solely to input and interaction (Chomsky, 1965).
Although it does not describe an optimal age for SLA, the theory implies that younger children can learn languages more easily than older learners, as adults must reactivate principles developed during L1 learning and forge an SLA path: children can learn several languages simultaneously as long as the principles are still active and they are exposed to sufficient language samples (Pinker, 1995). The parents of Singleton and Newport’s (2004) patient also had linguistic abilities in line with these age-related predictions; they learned ASL after puberty and never reached complete fluency.
Problems within UG Theory for L2 acquisition
There are, however, problems with the extrapolation of the UG theory to SLA: L2 learners go through several phases of types of utterance that are not similar to their L1 or the L2 they hear. Other factors include the cognitive maturity of most L2 learners, that they have different motivation for learning the language, and already speak one language fluently. Other studies also highlight these problems: DehaeneStanislas Dehaene
Stanislas Dehaene is a professor at the Collège de France, author, and director of INSERM . He has worked on a number of topics, including numerical cognition, the neural basis of reading and the neural correlates of consciousness. Dehaene was one of ten people to be awarded the James S...
(1999) investigates how cerebral circuits used to handling one language adapt for the efficient storage of two or more. He reports observations of cerebral activation when reading and translating two languages. They found the most activated brain areas during the tasks were not those generally associated with language, but rather those related to mapping orthography
Orthography
The orthography of a language specifies a standardized way of using a specific writing system to write the language. Where more than one writing system is used for a language, for example Kurdish, Uyghur, Serbian or Inuktitut, there can be more than one orthography...
to phonology
Phonology
Phonology is, broadly speaking, the subdiscipline of linguistics concerned with the sounds of language. That is, it is the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use...
. They conclude that the left temporal lobe is the physical base of L1, but the L2 is ‘stored’ elsewhere, thus explaining cases of bilingual aphasia where one language remains intact. They maintain that only languages learned simultaneously from birth are represented, and cause activity, in the left hemisphere: any L2 learned later is stored separately (possibly in the right hemisphere), and rarely activates the left temporal lobe.
This suggests that L2 may be qualitatively different from L1 due to its dissociation from the ‘normal’ language brain regions, thus the extrapolation of L1 studies and theories to SLA is placed in question. A further disadvantage of UG is that supporting empirical data are taken from a limited sample of syntactic phenomena: a general theory of language acquisition should cover a larger range of phenomena. Despite these problems, several other theorists have based their own models of language learning on it; amongst others Felix’ (1985) ‘competing cognitive systems’ idea. These ideas are supported by empirical evidence, which consequently supports Chomsky’s ideas. Due to this support and its descriptive and explanatory strength, many theorists regard UG as the best explanation of language, and particularly grammar, acquisition.
UG and the critical period hypothesis
A key question about the relationship of UG and SLA is: is the language acquisition deviceLanguage acquisition device
The Language Acquisition Device is a postulated "organ" of the brain that is supposed to function as a congenital device for learning symbolic language . First proposed by Noam Chomsky, the LAD concept is an instinctive mental capacity which enables an infant to acquire and produce language. It is...
posited by Chomsky and his followers still accessible to learners of a second language? Research suggests that it becomes inaccessible at a certain age (see Critical Period Hypothesis
Critical Period Hypothesis
The critical period hypothesis is the subject of a long-standing debate in linguistics and language acquisition over the extent to which the ability to acquire language is biologically linked to age...
), and learners increasingly depended on explicit teaching (see pedagogical effects above, and age below). In other words, although all of language may be governed by UG, older learners might have great difficulty in gaining access to the target language's underlying rules from positive input alone.
Piaget
PiagetJean Piaget
Jean Piaget was a French-speaking Swiss developmental psychologist and philosopher known for his epistemological studies with children. His theory of cognitive development and epistemological view are together called "genetic epistemology"....
(1926) is one psychologist reluctant to ascribe specific innate linguistic abilities to children: he considers the brain a homogeneous computational system, with language acquisition being one part of general learning. He agrees this development may be innate, but claims there is no specific language acquisition module in the brain. Instead, he suggests external influences and social interaction trigger language acquisition: information collected from these sources constructs symbolic and functional schemata (thought or behaviour patterns). According to Piaget, cognitive development and language acquisition are life-long active processes that constantly update and re-organise schemata. He proposes children develop L1 as they build a sense of identity in reference to the environment, and describes phases of general cognitive development, with processes and patterns changing systematically with age. Piaget assumes language acquisition is part of this complex cognitive development, and that these developmental phases are the basis for an optimal period for language acquisition in childhood. Interactionist approaches derived from Piaget’s ideas supports his theory. Some studies (e.g. Newport and Supalla, 1987) show that, rather than abrupt changes in SLA ability after puberty, language ability declines with age, coinciding with declines in other cognitive abilities, thus supporting Piaget.
Felix
Several researchers, however, remain unconvinced that language acquisition is part of general development: Felix (1985) claims cognitive abilities alone are useless for language learning, as only vocabulary and meaning are connected to cognition; lexicology and related meanings have conceptual bases. Felix’ criticism of the assumption that L2 fluency simply requires skilful applications of the correct rules is supported by the lack of psychological empirical evidence for Piaget’s idea.Krashen
Although KrashenStephen Krashen
Stephen Krashen is professor emeritus at the University of Southern California, who moved from the linguistics department to the faculty of the School of Education in 1994. He is a linguist, educational researcher, and activist.-Work:...
(1975) also criticises this theory, neither he nor Felix discredit the importance of age for second language acquisition. Krashen (1975), and later Felix (1985), proposed theories for the close of the CP for L2 at puberty, based on Piaget’s cognitive stage of formal operations beginning at puberty, as the ‘ability of the formal operational thinker to construct abstract hypotheses to explain phenomena’ inhibits the individual’s natural ability for language learning.
The term "language acquisition
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...
" became commonly used after Stephen Krashen
Stephen Krashen
Stephen Krashen is professor emeritus at the University of Southern California, who moved from the linguistics department to the faculty of the School of Education in 1994. He is a linguist, educational researcher, and activist.-Work:...
contrasted it with formal and non-constructive "learning." Today, most scholars use "language learning" and "language acquisition" interchangeably, unless they are directly addressing Krashen's work. However, "second language acquisition" or "SLA" has become established as the preferred term for this academic discipline.
Though SLA is often viewed as part of applied linguistics
Applied linguistics
Applied linguistics is an interdisciplinary field of study that identifies, investigates, and offers solutions to language-related real-life problems...
, it is typically concerned with the language system and learning processes themselves, whereas applied linguistics may focus more on the experiences of the learner, particularly in the classroom. Additionally, SLA has mostly examined naturalistic acquisition, where learners acquire a language with little formal training or teaching.
Effect of illiteracy
Virtually all research findings on SLA to date build on data from literate learners. Tarone, Bigelow and Hansen (2009) find significantly different results when replicating standard SLA studies with low literate L2 learners. Specifically, learners with lower alphabetic literacy levels are significantly less likely to notice corrective feedback on form or to perform elicited imitation tasks accurately. These findings are consistent with research in cognitive psychology showing significant differences in phonological awareness between literate and illiterate adults (Reis and Castro-Caldas 1997; Castro-Caldas et al. 1998). An important direction for SLA research must therefore involve the exploration of the impact of alphabetic literacy on cognitive processing in second language acquisition.Empirical research has attempted to account for variables detailed by SLA theories and provide an insight into L2 learning processes, which can be applied in educational environments. Recent SLA investigations have followed two main directions: one focuses on pairings of L1 and L2 that render L2 acquisition particularly difficult, and the other investigates certain aspects of language that may be maturationally constrained. Flege, Mackay and Piske (2002) looked at bilingual dominance to evaluate two explanations of L2 performance differences between bilinguals and monolingual-L2 speakers, i.e. a maturationally defined CP or interlingual interference.
Bilingual dominance
Flege, Mackay and Piske investigated whether the age at which participants learned English affected dominance in ItalianItalian language
Italian is a Romance language spoken mainly in Europe: Italy, Switzerland, San Marino, Vatican City, by minorities in Malta, Monaco, Croatia, Slovenia, France, Libya, Eritrea, and Somalia, and by immigrant communities in the Americas and Australia...
-English bilinguals, and found the early bilinguals were English (L2) dominant and the late bilinguals Italian (L1) dominant. Further analysis showed that dominant Italian bilinguals had detectable foreign accents when speaking English, but early bilinguals (English dominant) had no accents in either language. This suggests that, though interlingual interference effects are not inevitable, their emergence, and bilingual dominance, may be related to a CP.
Sebastián-Gallés, Echeverría and Bosch (2005) also studied bilinguals and highlight the importance of early language exposure. They looked at vocabulary processing and representation in Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...
-Catalan
Catalan language
Catalan is a Romance language, the national and only official language of Andorra and a co-official language in the Spanish autonomous communities of Catalonia, the Balearic Islands and Valencian Community, where it is known as Valencian , as well as in the city of Alghero, on the Italian island...
bilinguals exposed to both languages simultaneously from birth in comparison to those who had learned L2 later and were either Spanish- or Catalan-dominant. Findings showed ‘from birth bilinguals’ had significantly more difficulty distinguishing Catalan words from non-words differing in specific vowels than Catalan-dominants did (measured by reaction time).
These difficulties are attributed to a phase around age eight months where bilingual infants are insensitive to vowel contrasts, despite the language they hear most. This affects how words are later represented in their lexicon
Lexicon
In linguistics, the lexicon of a language is its vocabulary, including its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek "λεξικόν" , neut...
s, highlighting this as a decisive period in language acquisition and showing that initial language exposure shapes linguistic processing for life. Sebastián-Gallés et al. (2005) also indicate the significance of phonology for L2 learning; they believe learning an L2 once the L1 phonology is already internalised can reduce individuals’ abilities to distinguish new sounds that appear in the L2.
Age effects on grammar learning
Most studies into age effects on specific aspects of SLA have focused on grammar, with the common conclusion that it is highly constrained by age, more so than semantic functioning. B. Harley (1986) compared attainment of French learners in early and late immersion programs. She reports that after 1000 exposure hours, late learners had better control of FrenchFrench language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
verb systems and syntax. However, comparing early immersion students (average age 6.917 years) with age-matched native speakers identified common problem areas, including third person plurals and polite ‘vous
T-V distinction
In sociolinguistics, a T–V distinction is a contrast, within one language, between second-person pronouns that are specialized for varying levels of politeness, social distance, courtesy, familiarity, or insult toward the addressee....
’ forms. This suggests grammar (in L1 or L2) is generally acquired later, possibly because it requires abstract cognition and reasoning (B. Harley, 1986).
B. Harley also measured eventual attainment and found the two age groups made similar mistakes in syntax and lexical selection, often confusing French with the L1. The general conclusion from these investigations is that different aged learners acquire the various aspects of language with varying difficulty. Some variation in grammatical performance is attributed to maturation (discussed in B. Harley, 1986), however, all participants began immersion programs before puberty and so were too young for a strong critical period hypothesis to be directly tested.
This corresponds to Noam Chomsky
Noam Chomsky
Avram Noam Chomsky is an American linguist, philosopher, cognitive scientist, and activist. He is an Institute Professor and Professor in the Department of Linguistics & Philosophy at MIT, where he has worked for over 50 years. Chomsky has been described as the "father of modern linguistics" and...
’s UG theory, which states that while language acquisition principles are still active, it is easy to learn a language, and the principles developed through L1 acquisition are vital for learning an L2.
Scherag, Demuth, Rösler, Neville and Röder (2004) also suggest learning some syntactic processing functions and lexical access may be limited by maturation, whereas semantic functions are relatively unaffected by age. They studied the effect of late SLA on speech comprehension by German
Germans
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....
immigrants to the U.S.A. and American immigrants to Germany. They found that native-English speakers who learned German as adults were disadvantaged on certain grammatical tasks but performed at near-native levels on lexical tasks. These findings are consistent with work by Hahne (2001, cited in Scherag et al., 2004).
Semantic functions acquisition
One study that specifically mentions semantic functions acquisition is that of Weber-Fox and Neville (1996). Their results showed that ChineseChinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
-English bilinguals who had been exposed to English after puberty, learned vocabulary to a higher competence level than syntactic aspects of language. They do, however, report that the judgment accuracies in detecting semantic anomalies were altered in subjects who were exposed to English after sixteen years of age, but were affected to a lesser degree than were grammatical aspects of language. It has been speculated (Neville and Bavelier, 2001, and Scherag et al., 2004) that semantic aspects of language are founded on associative learning mechanisms, which allow life-long learning, whereas syntactical aspects are based on computational mechanisms, which can only be constructed during certain age periods. Consequently, it is reasoned, semantic functions are easier to access during comprehension of an L2 and therefore dominate the process: if these are ambiguous, understanding of syntactic information is not facilitated. These suppositions would help explain the results of Scherag et al.’s (2004) study.
Advantages of bilingual education for children
It is commonly believed that children are better suited to learn a second language than are adults. However, general second language research has failed to support the critical period hypothesis in its strong form (i.e., the claim that full language acquisition is impossible beyond a certain age).According to Linda M. Espinosa, especially in the United States the number of children growing up with a home language that is not English but Spanish is constantly increasing. Therefore these children have to learn the English language before kindergarten as a second language. It is better to dispose young children to maintain both, their home language and their second language. Cultivating his home language, the child creates his own cultural identity and becomes aware of his roots. This fact leads to the question whether having the ability to speak two languages helps or harms young children. Research shows that the acquisition of a second language in early childhood confers several advantages, especially a greater awareness of linguistic structures. Furthermore it is advantageous for young children to grow up bilingually because they do not need to be taught systematically but learn languages intuitively. How fast a child can learn a language depends on several personal factors, such as interest and motivation, and its learning environment. Communication should be facilitated rather than a child should be forced to learn a language with strict rules. Education in early childhood can lead to an effective educational achievement for children from various cultural environments.
Another aspect that is worth considering is that bilingual children are often doing code switching which does not mean that the child is not able to separate the languages. The reason for code switching is the child's lack of vocabulary in a certain situation. The acquisition of a second language in early childhood broadens the children's minds and enriches them more than it harms them. Thus they are not only able to speak two languages in spite of being very young but they also acquire knowledge about the different cultures and environments. It is possible that one language can dominate. This depends on how much time is spent on learning each language.
Hurford’s Model
In order to provide evidence for the evolutionary functionality of the critical period in language acquisition, Hurford (1991) generated a computer simulation of plausible conditions of evolving generations, based on three central assumptions:1. Language is an evolutionary adaptation that is naturally selected for.
2. Any given individual’s language can be quantified or measured.
3. Various aspects of maturation and development are under genetic control, which would extend to determine the timing for critical periods for certain capacities (i.e. polygenic inheritance).
According to Hurford’s evolutionary model, language acquisition is an adaptation that has survival value for humans, and that knowing a language correlated positively with an individual’s reproductive advantage. This finding is in line with views of other researchers such as Chomsky
Chomsky
Chomsky Khomsk ") is a Belarus'-origin surname, and may refer to:* Aviva Chomsky , American historian* Carol Chomsky , American linguist and wife of Noam Chomsky* Elsie Chomsky, American educator...
(1982) and Pinker & Bloom (1990). For example, Steven Pinker
Steven Pinker
Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...
and Paul Bloom argue that due to the fact that language is a complex design that serves a specific function that cannot be replaced by any other existing capacity, the trait of language acquisition can be attributed to natural selection.
However, while arguing that language itself is adaptive and “did not ‘just happen’” (p.172), Hurford suggests that the critical period is not an adaptation, but rather a constraint on language that emerged due to a lack of selection pressures that reinforce acquiring more than one language. In other words, Hurford explains the existence of a critical period with genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
, the idea that when there are no selection pressures on multiple alleles acting on the same trait, one of the alleles will gradually diminish through evolution. Because the simulation reveals no evolutionary advantage of acquiring more than one language, Hurford suggests that the critical period evolved simply as a result of a lack of selection pressure.
Komarova and Nowak’s Dynamical System
Komarova and Nowak (2001) supported Hurford’s model, yet pointed out that it was limited in the sense that it did not take into account the costs of learning a language. Therefore, they created their own algorithmic model, with the following assumptions:1. Language ability correlates with an individual’s reproductive fitness
2. The ability to learn language is inherited
3. There are costs to learning a language
Their model consists of a population with constant size, where language ability is a predictor of reproductive fitness. The learning mechanism in their model is based on Chomsky’s (1980, 1993) language acquisition device
Language acquisition device
The Language Acquisition Device is a postulated "organ" of the brain that is supposed to function as a congenital device for learning symbolic language . First proposed by Noam Chomsky, the LAD concept is an instinctive mental capacity which enables an infant to acquire and produce language. It is...
(LAD) and the notion of universal grammar
Universal grammar
Universal grammar is a theory in linguistics that suggests that there are properties that all possible natural human languages have.Usually credited to Noam Chomsky, the theory suggests that some rules of grammar are hard-wired into the brain, and manifest themselves without being taught...
. The results of their model show that the critical period for language acquisition is an “evolutionarily stable strategy
Evolutionarily stable strategy
In game theory and behavioural ecology, an evolutionarily stable strategy , which is sometimes also called an evolutionary stable strategy, is a strategy which, if adopted by a population of players, cannot be invaded by any alternative strategy that is initially rare. An ESS is an equilibrium...
(ESS)” (Komarova & Nowak, 2001, p. 1190). They suggest that this ESS is due to two competing selection pressures. First, if the period for learning is short, language does not develop as well, and thus decreases the evolutionary fitness of the individual. Alternatively, if the period for learning language is long, it becomes too costly to the extent that it reduces reproductive opportunity for the individual, and therefore limits reproductive fitness. Therefore, the critical period is an adaptive mechanism that keeps these pressures at equilibrium, and aims at optimal reproductive success for the individual.
See also
- Child developmentChild developmentChild development stages describe theoretical milestones of child development. Many stage models of development have been proposed, used as working concepts and in some cases asserted as nativist theories....
- Critical periodCritical periodThis article is about a critical period in an organism's or person's development. See also America's Critical Period.In general, a critical period is a limited time in which an event can occur, usually to result in some kind of transformation...
- Individual variation in second language acquisitionIndividual variation in second language acquisitionIndividual variation in second-language acquisition is a general term for studies in second-language acquisition that seek to address the question: Why do some learners do better than others? Unlike child language acquisition, people learning a second language rarely reach the same level of...
- Language acquisitionLanguage acquisitionLanguage acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...
- Multi-competenceMulti-competenceMulti-competence is a concept in second language acquisition formulated by Vivian Cook that refers to the knowledge of more than one language in one person's mind. From the multicompetence perspective, the different languages a person speaks are seen as one connected system, rather than each...
- MultilingualismMultilingualismMultilingualism is the act of using, or promoting the use of, multiple languages, either by an individual speaker or by a community of speakers. Multilingual speakers outnumber monolingual speakers in the world's population. Multilingualism is becoming a social phenomenon governed by the needs of...
- Second language acquisitionSecond language acquisitionSecond-language acquisition or second-language learning is the process by which people learn a second language. Second-language acquisition is also the name of the scientific discipline devoted to studying that process...