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Critical age

Patkowsky found that learners under

the age of fifteen achieved higher

syntactic(connected with syntax)

proficiency than those who were over

the age of fifteen at the onset of

exposure.

The study sought to discern if learners

who were exposed to second language

learning before the age of 15 actually

received higher syntactic proficiency

than older learners.

Johnson and Newport believe that after

the age of six, the ability to learn a

second language begins to decline.


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The results also show a correlation

between the age of acquisition and

the variance in the ultimate

performance in adults.

In the exercisehypothesis, it is believed

that humans easily learn languages at

an early age.

This hypothesis states that even though

humans have a capacity to learn

languages early in life, they are unable

to do so with the same outcome if

learning a second language commences

in the future

Lennebergs original proposal of a

critical period in language acquisition

seemed to predict a rectangular

function in the relationship between


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age of acquisition and ultimate

performance. That is, Lenneberg

hypothesized that normal language

learning was possible between the

period from infancy to puberty, with a

loss of abilities after puberty (p. 95)

In response to these and many other

empirical studies, Long (1990), in his

seminal paper, reviewed the second

language research on agerelated

differences. In this paper he draws

several conclusions that are relevant to

this topic: 1. Both the initial rate of

acquisition and the ultimate level of

attainment depend in part on the ageat which learning begins. 2. There are

sensitive periods governing both first


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and second language development,

during which both the acquisition of

different linguistic domains is

successful and after which it is

incomplete. 3. The age-related loss of

ability is cumulative, not a one-time

event. 4. Deterioration in someindividuals begins as early as six.

Starting after age six appears to make

it impossible for many learners (and

after age 12 for the remainder) to

achieve native-like competence in

phonology; starting later than the early

teens, more precisely after age 15,

seems to create the same problems inmorphology and syntax. (p. 274)


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there is an ideal 'window' of time to

acquire language in a linguistically rich

environment, after which this is no

longer possible due to changes in

the brain.

Various ages have been proposed for

the supposed end of the CPH; those

that point to pre-adolescent ages such

as 12 have been vulnerable to

alternative theories which

invoke psychological or social factors

applying as children move

into adolescence.

The hypothesis was developed by Eric

Lenneberg in his 1967 Biological

Foundations of Language, which set the


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end of the critical period for native

language acquisition at 12

In SLA, a weaker version of the CPH

emerged in the 1970s. This refers to

a sensitive periodin which nativelike

performance is unlikely but not ruled

out.[2] The strongest evidence for the

CPH is in the study of accent, where

most older learners seem not to reach

a native-like level.

First language acquisition

For more information, see: First

language acquisition.

Children without language

The CPH as applied to first language

acquisition proposes that a child

deprived of exposure to natural


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language would fail to acquire it if

exposure commenced only after the end

of the critical period. Because testingsuch a theory would be unethical, in

that it would involve isolating a child

from the rest of the world for several

years, researchers have gatheredevidence of the CPH from a few victims

of child abuse. The most famous

example is the case of Genie (a

pseudonym), who was deprived of

language until the age of 13. Over the

following years of rehabilitation,

improvement in her ability

to communicate was noted, but during

this time she did not develop thelanguage ability common to other

children.[5] However, this case has been

criticised as a firm example of the


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critical period in action, and data has

not been gathered from Genie since the

1970s.[6]

Although there are several cases on

record of deaf children being deprived

of sign language, this could also count

as abuse. One case in which no abusetook place is that of Chelsea, whose

deafness was left undiagnosed until the

age of 31. Once hearing aids had

apparently restored her hearing to near-

normal levels, she seemed to develop a

large vocabulary while her phonology

and syntax remained at a very low

level.[7] The implications of this have

been disputed, given the apparently

unlikely circumstances of Chelsea's

diagnosis.[8]


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Many researchers hold opposing beliefs

about the Critical Period Hypothesis

put forth by Lenneberg (1967). The

hypothesis cited in Lightbown and

Spada (1999) states that there is a

specific and limited time period for

language acquisition (p. 19).Lenneberg believed that the language

acquisition device, like other biological

functions, works successfully only when

it is stimulated at the right time (p.19).

2.2 The critical period hypothesis

for language acquisition

In the field of language acquisition,the hypothesis that there is a critical

or


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sensitive period for language

acquisition plays an important role.

In the latefifties and sixties, Penfield and

Roberts (1959) and Lenneberg

(1967) were

the first to propose that there was acritical period for language

acquisition.

They based this proposal on

different types of evidence:

- evidence from feral and abused

children who grew up without being

exposed to human language in

childhood and who did not acquire

language normally after they werefound


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- evidence from deaf children whose

development in spoken language

stopped after puberty- evidence that children with aphasia(

recovered much better than adults

with aphasia

All this evidence comes from first

language acquisition.

2.2. Studies of a Human Brain and its

Lateralization

If a language develops with the

increase of the brain cell connections,

the development of language and brain

should bear some relation to each

other. Physiological functions of

neuronal cells, circuits, or connections

themselves have not been identified

clearly so far, but some specified fields


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of linguistic functions have been

reported. Geschwind (1980:62-63)

claims:

Although the content, that is, the

specific language learned, is completely

determined by the environment, the

capacity to acquire language isbiologically determined. Indeed, one

should not speak about a contrast

between language and general

cognitive ability.

Earlier studies show that the brain

seems to have special-purpose

computers for limited functions, and

there is at present no evidence of any

all-purpose computer for any generalcognition. If a language is acquired in

parallel with the development of the

human brain as children grow, it is


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reasonable to postulate(to suggest /

accept the existence,fact,or truth of

something as a basis of reasoning ortheory)some language function in the

brain. Consequently, the critical period

for language learning is considered to

be the biologically determined period

in which the brain keeps its plasticityfor acquisition of any language.

At first it was expected that the

function of human language acquisition

was clarified by exploring a specialstructure, which all other animal brains

lack. The brain of human beings

consists of a left hemisphere and a

right hemisphere, and different

functions are said to develop graduallyin different parts of the brain as

children grow older. The parts of brain

which control a language are placed in


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the left hemisphere after its

lateralization(. One of the parts is called

the Broca's area and the other part iscalled the Wernicke's area. The study

of aphasia has revealed that the Broca's

area controls spoken language. The

Wernicke's area is, on the other hand,

said to be the center of languageunderstanding.

Lenneberg posits that the development

of language is the result of brain

maturation. Although bothhemispheres of the brain are equal at

birth, the function of language

gradually settles in the dominant left

hemisphere of the brain after biological

maturation or the critical period. Thatis, the critical period for language

learning has been considered to agree

with the period of the lateralization of


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brain. Research on people who have

suffered brain damage also supplies the

evidence for the lateralization ofbrains. Lenneberg viewed clinical data

and claimed that children younger than

nine years old had a higher incidence of

right hemisphere lesions (damage

caused by injury or illness) causingaphasia than adults (Villiers & Villiers

1978:211). Another support of

lateralization is an experimental report

of speed and accuracy in language

acquisition by Kimura (1973). He

examined speech sounds heard in each

ear. His result is that speech sound

through the right ear is processed more

quickly than through the left earbecause the left hemisphere is

connected to a right ear.


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A brain is said to lose its plasticity after

the lateralization, and some case

studies are reported on the impairedbrains before and after the critical

period. Adults who have suffered brain

damage in their left hemisphere fail to

recover their language if they don't

recover in five months, but childrenshow an ability to recover over a longer

period, and have sometimes made a

full recovery if they were very young at

the time of damage (Crystal 1987:263).

Even total removal of the left

hemisphere did not preclude children's

reacquisition of language. Lenneberg's

argument is based on this period of

lateralization, of which completionmeans the end of the critical period.


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2.4. Criticism of the Critical Period

Hypothesis

2.4.1. Critical Period Hypothesis

reexamined

As medical science has progressed, some

points in Lenneberg (1967) are under

criticism. Firstly, his claim that the CPHcould be supported by the study of Down's

syndrome cases is attacked. According to

his argument, the development of children

with Downfs syndrome is so slow that

they pass their critical period for language

learning. However, a recent survey

disputes his claim because children with

Down's syndrome have a build-in endpoint

to their ability (Gleitman 1984).

Secondly, the theory of brain's

lateralization at the age of two, with the


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critical period set by Lenneberg (1967), is

also criticized. He claimed that children

before their critical period were lessseverely impaired by brain damage.

However, Krashen (1973) reexamined the

data used in Lenneberg (1967) and found

all the cases of complete recovery from

aphasia were under the age of five.

Surprisingly, the number of cases of

recovery at the age of more than five or

over was nearly the same number as the

adults'. Kinsbourne (1975) pointed out the

difficulty in deciding whether only half of

the hemisphere was injured or not.

Another piece of counter evidence is seen

inMacKain et. al. (1983). Their experiment

with babies of six months or less shows

that lateralization begins much earlier

than two years old. If so, lateralization

cannot be the evidence of the critical

period. Reports of dichotic listening,

experiments in which different stimuli are


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presented simultaneously to the two ears,

also show that language functions are

lateralized much earlier than the criticalperiod. Regrettably, no conclusive

evidence for right ear advantage based on

the lateralization has not been reported.

Thirdly, the case studies of three

linguistically isolated children have someproblems. Because the early research in

Isabelle's case was not written by a

specialist in language (Aitchson 1989:86),

her speech may have been less sufficient

than reported. There is also a report thatGenie's left hemisphere was atrophied

because of the brain damage. This implies

that she used only the right hemisphere of

the brain, the part which is said to have

little function in language processing.Curtiss, et. al. (1974) writes:

The result of the dichotic tests using

environmental sounds also show a left-ear


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advantage, but only to a degree found in

normal subjects. This 'normal' result

shows that Genie is not simply one ofthose rare individuals with reversed

dominance, but instead is one in whom all

auditory processing currently appears to

be taking place in the right hemisphere

(Curtiss, Fromkin, Krashen, Rigler, and

Rigler 1974:542).

Isabelle was deaf and Chelsea had hearing

problems too (Aitchson 1989:87). A

difference between deaf and normal

children should have been taken intoconsideration in the case studies. Since no

further case of feral children will be

reported, the data have been reanalyzed.

All of these criticisms of the past studies

show how difficult it is to connect brainfunctions and language acquisition.

Moreover, the different methods for the

research on the CPH have also resulted in


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varieties of inconsistencies. For example,

native speakers were asked to rate the

performance or naturalness of theutterances of learners in one study (Scovel

1981, cited in Ellis 1984:485), whereas

grammatical judgments made by learners

of different ages were examined in

another study (Coppetiers 1987). Birdsong

(1992) designed a grammaticality

judgment test for twenty native English

speakers who spoke French with native-

like fluency in order to examine Long's

question (1990:281) of 'whether the very

best learners actually have native-like

competence.'

The critical period hypothesis (CPH) refers

to a long-standing debate

in linguistics and language acquisition over

the extent to which the ability to


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acquire language is biologically linked

to age. The hypothesis claims that there is

an ideal 'window' of time to acquirelanguage in a linguistically rich

environment, after which this is no longer

possible due to changes in the brain. The

hypothesis has been discussed in the

context of both first (FLA) and second

language acquisition (SLA), and is

particularly controversial in the latter. In

FLA, it seeks to explain the apparent

absence of language in individuals whosechildhood exposure was very limited, and

in SLA it is often invoked to explain

variation in adults' performance in

learning a second language, which is very

often observed to fall short

of nativelike attainment. Various ages

have been proposed for the supposed end


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of the CPH; those that point to pre-

adolescent ages such as 12 have been

vulnerable to alternative theories whichinvoke psychological or social factors

applying as children move

into adolescence

History

The critical period hypothesis is associated

with Wilder Penfield, whose 1956

Vanuxem lectures at Princeton

University formed the basis of his 1959

work with Lamar Roberts, Speech andBrain Mechanisms. Penfield and Roberts

explored the neuroscience of language,

concluding that it was dominant in the left

hemisphere of the brain on the basis of

hundreds of case studies spanning manydecades. The review focussed on how

individuals with brain damage evidenced

atypical linguistic performance, rather


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than examining neurotypical cases of

'normal' language acquisition, and the

authors' conclusions were also based onthe prevailing tabula rasa view that

children were born without any

real innate language ability; however,

linguistic "units", once "fixed", would

affect later learning.[1]

Their

recommendations for language schooling

recommended starting early in order to

avoid fixed effects; though these claims

did not form the core of the book, being

confined to the last chapter, other

researchers and popular opinion were

much-influenced by them. The hypothesis

was developed by Eric Lenneberg in his

1967 Biological Foundations of Language,

which set the end of the critical period for

native language acquisition at 12. The

hypothesis has been fiercely debated since

then, and has continued to inform popular

assumptions about the presumed


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(in)ability of adults to fluently learn a

second language.

In SLA, a weaker version of the CPHemerged in the 1970s. This refers to

a sensitive periodin which nativelike

performance is unlikely but not ruled

out.[2]

The strongest evidence for the CPH

is in the study of accent, where most olderlearners seem not to reach a native-like

level. This leads some researchers to apply

the CPH only to second

language phonology rather than all

aspects of language; indeed, a CPH wasnot seriously considered for syntax until

the 1990s, in research that remains a

minority view.[3]

However, under certain

conditions, native-like accent has been

observed, suggesting that accent in SLA isaffected by multiple factors, such

as identity and motivation, rather than a

biological constraint.


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Children without language

The CPH as applied to first language

acquisition proposes that a child deprivedof exposure to natural language would fail

to acquire it if exposure commenced only

after the end of the critical period.

Because testing such a theory would be

unethical, in that it would involve isolatinga child from the rest of the world for

several years, researchers have gathered

evidence of the CPH from a few victims

of child abuse. The most famous example

is the case of Genie (a pseudonym), whowas deprived of language until the age of

13. Over the following years of

rehabilitation, improvement in her ability

to communicate was noted, but during

this time she did not develop the languageability common to other

children. However, this case has been

criticised as a firm example of the critical


27/27

period in action, and data has not been

gathered from Genie since the 1970s.

Although there are several cases on recordof deaf children being deprived of sign

language, this could also count as abuse.

One case in which no abuse took place is

that of Chelsea, whose deafness was left

undiagnosed until the age of 31.Once hearing aids had apparently restored

her hearing to near-normal levels, she

seemed to develop a large vocabulary

while her phonology and syntax remained

at a very low level. The implications of thishave been disputed, given the apparently

unlikely circumstances of Chelsea's

diagnosis.

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