Does Critical Period Play a Role in Second language acquisition.pdf

Does Critical Period Play a Role in Second language acquisition?

Reviewed By: Indrani Chakravarty, Y0146

What is a critical period?:

It is a “maturational time period during which some crucial experience will have its peak

effect on development or learning, resulting in normal behavior attuned to the particular

environment to which the organism has been exposed.”[5]. This implies there are certain

crucial experiences to which the organism must be exposed within a specific time period,

else there will be a reduced effect or no effect at all of the experience if learnt outside the

specific time period. The first example [1,3,5] which comes to our mind is the famous

example of Professor Conrad being followed by a flock of geese, as if he was their

“mother”. The reason behind this weird behavior is obvious. The flock of geese was

isolated from their parents right after birth. So, they identified Professor Conrad as an

attachment object instead of identifying a species member as the attachment object

(‘imprinting’). Later, when the same flock was exposed to their original parents (after a

specific time period had passed), the geese failed to recognize their parents. Another

classic example [1,3,5] of the existence of critical period is the case of white crowned

sparrows. When these sparrows were brought up in isolation, they sang a very crude song

which had some structural similarities with the original sparrow song. However, when

they were exposed to a tape recorded sparrow song within 10-50 days of their birth, they

picked it up very nicely, but if they were exposed after this time period had passed, they

continued singing the crude songs. All these examples show that the concept of critical

period does exist among other species.

Concept of Critical Period among humans:

His hypothesis was based on three groups of people—[1, 3, 5]

• People who had brain damage through accidents or disease before puberty had

irreversible damage to their language functions, and were unable to pick up

those functions when intensive speech therapy was given after puberty.

• Children with Down's syndrome, whose general body development was

slower than any other normal children, had their language development slower

too. To be noted, their language development halted at puberty.

• Isolated children who have not been spoken to during the crucial period of

childhood; referred to as "wild children" .

The concept of critical period among human beings was developed by analogy with the

learning mechanisms in other species and was proposed by Penfield and Roberts (1959).

One of his most prominent supporters Eric Lenneberg [1, 3, 4, 5] hypothesized in his

book Biological Foundations of Language (1967) [1, 3, 5] that

• “Language acquisition is a Biologically constrained learning” [3]

• “Normally acquired during a critical period( early in life and puberty)”[3]

• “Outside this period, language acquired through a different learning process or

with difficulty”[3].

To prove that his hypothesis was correct, Lenneberg cited an example [1] of 13 yrs old

mentally abused girl Genie who used to be kept isolated ever since she was just a few

months old, and hence was not given any exposure to language environment. After her

rescue, she received intensive speech therapy, but, was not able to construct grammatical

sentences even after prolonged treatments. Lenneberg concluded that since the critical

period during which she should have had the exposure to language environments had

passed, she could not acquire the language later on too. But, there was confusion in the

explanation given by Lenneberg--was it the critical period or the brain damage that

resulted from the physical and mental abuse endured by Genie the cause that prevented

her from acquiring the language?

Pinker on account of his support to Lenneberg’s hypothesis cited another example [1] of

a woman known in the literature as "Chelsea" whose deafness was only discovered at the

age of 31. Unlike Genie, she was not abused mentally or physically, but her language

acquisition pattern after hearing aids were fitted was quite similar to Genie's pattern of

significant vocabulary acquisition but little grasp of syntax. Pinker suggested that Chelsea

was given the hearing aids and speech therapy after her critical period had passed. But,

even this citation met with a lot of controversies--why wasn’t her deafness revealed

before the age of 31?

Despite the controversies, the critical period hypothesis continued to exist, since it

received support from the fact that language development of children with Down's

syndrome halted at puberty. It was also found that abused children isolated from exposure

to first language showed deficits in phonology, morphology, and syntax [1, 5]. General

physical and cognitive status may be a concern for such children, which may not really be

a matter of concern for normal children and adults [1, 5]. Normal adults during the first

few months of learning have an advantage over children in case of higher acquisition of

vocabulary and speed of learning, but people who start early produce lesser grammatical

mistakes than those who start late. In fact, children have a “flawless control over the

accent and rhythm of language and full productive control over syntax and morphology”

[5] if they start early. With increasing ages of exposure, beginning from 4-6 yrs, there is a

gradual decline in language proficiency until it plateaus for adult learners (Johnson and

Newport, 1989; Newport 1990) [5]. That is learners exposed to the language in adulthood

show lower performance than those who are exposed in early childhood. (Johnson and

Newport,1989) [5]. The effects have mainly been seen in degree of accent, morphology

and syntax. Therefore, it was concluded that critical periods affect phonology,

morphology and syntax, not the vocabulary and semantic processing (occurs relatively

normally in late learners) of language acquisition, be it first or second.

Johnson and Newport’s Study [3, 5]:

Johnson’s and Newport’s wanted to find out whether this applies to both the first and

second language acquisition. They conducted a survey on a sample consisting of native

speakers of Korean and Chinese who had immigrated to the US at different ages.

[1,3,4,5]. The subjects were asked to make grammaticality judgments about 276 English

sentences. Half the sentences were rendered ungrammatical by violating rules about

articles, gender agreement and verb structures. The seven subjects who had arrived

between ages 3 and 7 performed indistinguishably from native speakers of English. A

strongly negative correlation between age of arrival (especially before 15) and ability to

judge grammaticality was observed for children, but for the adult learners there was no

significant correlation between age of arrival and grammaticality judgment ability.

They concluded that [1, 3, 4, and 5]

• A critical period does exist for the acquisition of grammar and the effects are

seen for both first and 2nd languages.

• They reported that prior to age 15, there was a very strong negative correlation

with age but after age 15, there was no correlation with age. Therefore age 15

was considered to be the end point of the critical period.

Pinker supported this conclusion heavily and summed it up as “acquisition of a normal

language is guaranteed for children up to the age of six, is steadily compromised from

then until shortly after puberty, and is rare thereafter” [3].

The questions [5] that arose

• Does the L1 acquisition affect the L2 acquisition?

• Does it reduce the effects of later stage learning?

As an answer to these questions, it was found that late first language acquisition results in

lower performance than does the 2nd language acquisition, regardless of signed or

spoken languages. [Newport]. So, does it imply that L1 has no effect on L2?

There were also two challenging evidences that the critical period hypothesis had to

account for—

• The identification of older learners who achieve native- like competence in

the second language (Birdsong, 1992)

• Behavioral evidence that fails to reveal a qualitative change in learning

outcomes at the close of a critical period (Bialystok & Hakuta, 1999).

If the critical hypothesis is to be true then these evidences should not be correct; on the

other hand if they are taken correct, then the hypothesis should be wrong.

Two Hypotheses on how L1 acquisition affects L2 acquisition:

• Does L2 acquisition recapitulate the L1 acquisition? [3]. If L2=L1 Hypothesis

is to be correct, then the critical period of L1 acquisition relevant to L2

acquisition.

• Is L2 acquisition a cumulative process that builds on the competence already

developed in L1? [3] If yes, then critical period of L1 acquisition irrelevant to

L2 acquisition.

Let us take an example of two native Chinese and Spanish speakers who are trying to

learn English. The speaker of Spanish will acquire English more rapidly than would a

native speaker of Chinese, all other things being equal, because of the linguistic similarity

between Spanish and English. This evidence would imply that the cumulative model is

correct.

However, there is a remarkable similarity across speakers of different languages learning

a given L2, indicating that “there is much more than simple transfer from L1 to L2 going

on (Bialystok & Hakuta, 1994) and that indeed there is some sort of reenactment of the

L1 acquisition process at work”[3].

To solve the conflict between the two hypotheses, Lenneberg, the originator of the

critical period hypothesis, said [3] “we may assume that the cerebral organization for

language learning as such has taken place during childhood, and since natural languages

tend to resemble one another in many fundamental aspects, the matrix of language skills

is present” (p. 176), which indicates he favored the cumulative model.

Characteristics of a Critical Period:

A critical period must have two characteristics (Bornstein, 1989; Columbo, 1982) [5]--

“High level of preparedness for learning within a specified developmental period to

assure the domain is mastered by the species”, and “lack of preparedness outside of this

period”.

If the critical period hypothesis is to be correct, then the following conditions must be

satisfied--

Condition 1 [3]: “There should be clearly specified beginning and end points for the

period”. To this, Lenneberg suggested puberty, Johnson and Newport suggested age 15,

Pinker suggested between age 6 and end of puberty.

Condition 2 [3]: “There should be a well-defined decline in L2 acquisition at the end of

the period, not a monotonic decline with age”. This will be true if there is a drastic

change decline in gradient or mean around the end of the critical period, rather than a

general monotonic decline with age that continues throughout the life span.

Condition 3 [3]: “There should be evidence of qualitative differences in learning between

acquisition within and outside the critical period”. That is, there should be distinct

differences between the patterns of acquisition between child and adult second language

learners. This component of the hypothesis will be true if certain grammatical errors

could be found among adult learners that are never found in child learners or if child

learners were able to learn specific aspects of the language that no adults could learn.

Condition 4[3]: “There should be robustness to environmental variation inside the critical

period”. It is true if “within the critical period, even with considerable environmental

variation, the outcomes are uniform, but beyond that period, the outcomes are variable”.

Figure 1: Theoretical Predictions [3]

Figure 1 is the theoretical predictions of the critical period hypothesis. In both the figures,

specific end points exist with a sharp drop (qualitative and quantitative) in the language

proficiency at the end of the critical period. Also there is a robustness to the

environmental conditions is displayed within the critical period (uniformity inside).

Re-analysis of Johnson’s and Newport’s Study by Bialystok and Hakuta in

1994[3,4]:

Johnsons and Newport had concluded from their experimental survey that age 15 was the

end point of the critical period. When the same data was reanalyzed by Bialystok and

Hakuta, it was found that there was a discontinuity at age 20 and not at age 15(Figure 2).

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