Topic 2: After the critical period, most individuals face difficulties in learning a language. Using

Lenneberg’s Critical Period Hypothesis and other psycholinguistic evidence, discuss

this phenomena.

Introduction

Throughout the years, psycholinguists and linguists alike have tried to come up with

explanations that account for how humans are able to acquire and learn language(s). Sadly, no

one was able to come to an agreement on the exact science behind human language acquisition.

What they do agree however, is that language acquisition and language learning are two entirely

different things. Language acquisition refers to an acquisition of language outside of a classroom

(Brown, 2007). This usually refers to our mother tongue or our first language that we ‘pick up’

as a young child in an informal environment. Language learning on the other hand, is the exact

opposite of language acquisition. It refers to the ‘conscious’ learning of a language in a

classroom or a formal environment. This normally would be any subsequent language learnt after

the first language.

One of the major breakthroughs in hypothesising the phenomena behind language

learning and acquisition was made by Eric Heinz Lenneberg (1921-1975). Lenneberg was a

linguist and neurologist who pioneered ideas on language acquisition and cognitive psychology.

He was a staunch believer in the innateness movement. Born in Düsseldorf, Germany he left the

country with his family in 1993 due to the rising of Nazi persecution (Eric lenneberg 1967, n.d).

The family originally settled in Brazil but he soon went to United States and furthered his studies

at the University of Chicago and Harvard University. He obtained his PhD in psychology and

linguistics and taught at Harvard Medical School, the University of Michigan in Ann Arbor and

Connell University as a professor of psychology and neurobiology.

Among all of his researches, Lenneberg most famous study involved the well known

Critical Period Hypothesis, which he popularised in his publication, Biological Foundations of

Language in 1967. In it, he hypothesised that:

i) Language learning is a biologically constrained learning;

ii) Language is normally acquired during a critical period (early in life and puberty)

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iii) Outside this period, language will be acquired through a different learning process

or with difficulty.

Critical Period Hypothesis

The Critical Period Hypothesis (CPH) was first proposed by neurologist Wilder Penfield

and co-author Lamar Roberts in 1959 but was popularised by Lenneberg in 1967 with his

publication, Biological Foundations of Language (David, 2007). One of the major supporters of

CPH includes linguist, Noam Chomsky. CPH is based heavily on the assumption that language is

biologically based and the ability to learn a native language is developed within a fixed period,

from birth to middle childhood (Fromkin, Rodman, & Hyams, 2007).

The critical period here refers to a time frame during which some crucial experience will

have its peak effect on development or learning which could result in a swift and easy process of

language acquisition attuned to the particular environment to which the organism has been

exposed to. So, if an American child is exposed to Mandarin before his puberty, it is very likely

that the child will be able to speak Mandarin like a native. However after this period, the

acquisition of grammar would be difficult and for many, never fully achieved. Children who

were deprived of language during this critical period have been known to show atypical patterns

of brain lateralisation.

Generally, all critical periods; human or animals, shares a slightly similar geometric

feature (Boxtel, 2005). The critical periods will have an onset, a peak of heightened sensitivity,

an offset and a terminus with a flattening after the terminus (refer to figure 2.1 in Appendix).

What this means is that during the onset, the organism involved will have an acute sensitivity

towards the environment or stimuli. When it reaches the peak, exposure to the stimuli or

environment will be very effective. This continues on until it reaches the terminus indicating the

end of the critical period. The “flattening” relates to Lenneberg’s belief that once the child hits

puberty the stimuli will no longer be effective because the critical period has ended. To tie it

back to the problem statement, when a child has reached puberty according to Lenneberg, the

child will not be able to learn a language easily.

While the topic of CPH for humans is widely debated, it has been proven that there is a

concept of critical period for other species. Ducklings for example were found; much to the joy

of Konrad Lorenz (Lorenz, 1973), to imprint on and follow the first moving object they see,

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whether or not it looks or waddles like a duck during the period from nine to twenty-one hours

after hatching (Chakravarty, n.d.). Another species that is seen to have a critical period in

learning a language is the white crowned sparrow. When brought up in isolation from a few days

after birth, the birds would sing crude songs containing basic structures to the original white

crowned sparrows’ songs. However, if the birds were trained using a tape recorder within a

specific time period (10-50 days after birth), they will eventually be able to sing the songs

properly. The birds that were exposed to the tape after the period will see little to no effect on the

quality of the songs sung.

The critical period seemed to relate to species-specific, biologically triggered behaviours

(Fromkin, Rodman, & Hyams, 2007). The behaviour of the ducks and the sparrow were not the

result of a conscious decision, external teaching or intensive practice but rather due to what

appeared to be a maturationally determined schedule that is universal across the species.

Evidence for such a period to exist for humans are however, limited and support for this

hypothesis comes largely from theoretical arguments and analogies but is nonetheless widely

accepted. Be that as it may, Lenneberg seems to be of the mind that CPH does exist for humans

and according to Boxtel (2005), Penfield and Roberts (1959) and Lenneberg (1967) based their

CPH on several pieces of evidence which were;

i) Evidence from feral and abused children who had no exposure to human language in

their childhood and were unable to acquire language normally after found

ii) Evidence from deaf children whose development in spoken language stopped after

puberty.

iii) Evidence that children with aphasia recovered better than adults with aphasia

Brain Lateralisation

According to Brown (2007), one of the most promising areas of inquiry in age and

acquisition research is the study of the functions of the brain in the process of acquisition. Some

believe that brain lateralisation is the key to answering the question of language acquisition

because there is neurological evidence that as the brain matures; certain functions are assigned,

or “lateralised”, to the left hemisphere of the brain while other functions to the right hemisphere.

Indeed, brain lateralisation is one of the key concepts used to support the CPH.

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The foundation of CPH lies on the neurological research that suggests that after puberty,

the brain functions will become lateralised (Moore, 1999). Intellectual, logical and analytical

functions appeared to be mostly located in the left hemisphere while the functions pertaining to

emotional and social needs are catered by the right hemisphere (See Appendix for list of

functions performed by both hemispheres). It is believed that the functions are not completely

assigned to either portion of the brain before puberty.

During the period before puberty reaches the child, the brain is considered extremely

elastic (flexible). Following the line of thought for CPH, the prepubescent brain is like a

“sponge” where all learning, knowledge and experiences will be ‘absorbed’. The ‘absorption’ of

language to nonspecific areas in the brain supposedly makes the learning of a language; first or

second, easier for the child compared to that of an adult or older adolescents. After the brain has

been lateralised, it is widely believed that language functions appeared to be mainly controlled in

the left hemisphere although there is some contention pertaining to the location and functions of

the hemispheres.

This is due largely to the fact that children with prenatal, perinatal, or childhood brain

lesions in the right hemisphere has the possibility to show setbacks and impairments in babbling

and vocabulary learning while children with early left hemisphere lesions demonstrate

impairments in their capability to form phrases and sentences (Fromkin, Rodman, & Hyams,

2007). There are also cases where children who had a right hemispherectomy (surgery on the

brain’s left hemisphere) could not develop language abilities despite having a left hemisphere.

Be that as it may, many findings add up to show that, generally, the left hemisphere of the brain

is essentially made for language while the right hemisphere is involved with a child’s early

language development.

It has been found that children up to the age of puberty who suffered injuries to the left

hemisphere were able to re-localise linguistic functions to the right hemisphere, to ‘relearn’ their

first language with relatively little impairment under the right circumstances. One such case was

found in a longitudinal study of a boy who had no speech at 8 years of age after going through a

left hemispherectomy but was able to recover his speech capabilities when he was 9 years old

(Brown, 2007). Conversely, surgical removal of the left hemisphere in adults will indubitably

result in severe loss of their language abilities. Of course it goes without saying that removal of

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the right hemisphere will allow adults and children to retain their language abilities so long as

they meet the right circumstances.

In order to answer the problem statement of this assignment, what is crucial here is

actually not where the language functions are lateralised but when exactly the lateralisation takes

place and whether the process affects language acquisition.

Lenneberg suggested that the slow process of lateralisation begins around the age of 2

and is completed around puberty (Brown, 2007). Take note that the age for the critical period

varies in different accounts and, linguists and psychologists are unable to pinpoint an exact age

for the critical period. During the critical period, the child is presumed to neurologically assign

functions little by little to one side of the brain or another.

It was suggested that the plasticity of the brain prior to puberty is the reason why children

are able to acquire their first language and any subsequent languages without any hindrances. It

may be possible that because of lateralisation, adults are finding it harder to acquire a second

language with the proficiency of a native speaker because they have lost their brain’s elasticity.

Second language learners who started after puberty were found to use more of their right

hemisphere than the first language learners did. Obler (1981) and Genesee (1982) found that

individuals, who acquire their second language late relative to their first language, used more of

their right brain. Brown and other researchers also observed more activity in the right

hemisphere of the brain during the early stages of second language acquisition (Brown, 1994).

Now that the CPH has been explained in terms of brain lateralisation, the next section

will explain other psychological theories that support it.

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Support from Other Psychological Theories

As mentioned before, Noam Chomsky is one of the notable proponents for CPH.

Chomsky developed the innateness hypothesis, a linguistic theory of language acquisition

where it is believed that language acquisition is innately determined. The hypothesis is supported

by an observation that the grammar a person ends up with is mostly not determined by linguistic

experience because language acquisition is a creative process. This can be seen when children

who are not given explicit information about the rules of a language are able to extract the rules

from what they hear and make sentences based on the rules they gained (Fromkin, Rodman, &

Hyams, 2007). It has been revealed through observations that children of different culture and

social circumstances acquire language in a similar manner.

That is why Chomsky stated that environmental factors are irrelevant to language

emergence, because there are many factors surrounding the children while they are acquiring

their first language. He used the existence of an innate knowledge to explain how a child is able

to master a native language in such a short period of time even though the rules of language are

highly abstract in nature.

Chomsky and some linguists believed that humans are equipped with an innate template

or blueprint for language known as the Universal Grammar (UG). UG is a collection of rules that

represents the universal properties of all languages which allows it to provide a basic blueprint

that all languages follow. In other words, UG provides the basic design for all human languages

and individual languages like English, Mandarin, Tamil or any other languages are simply

variations of the basic design. It specifies the different components of grammar and their

relations, how the different rules are constructed and so on.

For example, all languages no matter whether if they are eastern or western language,

have phrasal structure rules where all phrase will contain complements and head but not all

languages will have the same word order. An illustration of this would be where English

Language has the word order of S-V-O (Subject followed by verb and object) but Japanese has

the word order, S-O-V (Subject followed by object and then verb).

These differences in language are called parameters. Chomsky believed that children will

set the parameter at the correct value for their language thus allowing them to rapidly and easily

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acquire a language. This is because the parameter of UG limits the grammatical options to a

small defined set which helps to reduce the acquisition burden on the child.

UG is presumed to be contained in a ‘language acquisition device’ (LAD); a

metaphorical “little black box” in the brain which restricts the possibilities for variations within a

language while enabling learners to construct grammar rules out of ‘raw input’ collected from

the environment. Chomsky proposed that all humans were born with an LAD that begins

functioning when they are still babies. The device enable humans to learn from their

environment so that by the time they reach the age of five or six, they would have a set of rules

for their native language or first language based on the universal grammar.

UG was developed to explain first language acquisition but it can also be applied to

second language learners who are able to achieve near-native fluency not solely on input and

interaction. Those who learn during the “critical period” will be able to acquire language without

any effort. However, our LAD will begin to function in different ways after we reach six years of

age. We remain able to acquire language fairly easily until we reach puberty, after which the

ability to do so seemed to be reducing. Older learners must therefore learn languages in quite

different ways from the effortless acquisition of young children. UG can also be applied to

explain why adults will have difficulty in learning a language.

As mentioned previously, children will set their UG’s parameters according to the

language used in their environment. Although it helps a child to easily acquire a language it will

also affect the child’s ability to learn a language after reaching puberty. The hypothesis is that

parameter setting is done early in development and cannot be undone (Fromkin, Rodman, &

Hyams, 2007).

What this mean is that once a person tries to learn a language after puberty, they will face

difficulties because the parameters for that language was not set earlier on before puberty. For

example, an American child was able to acquire English easily when he was young because the

parameters were set for English language through the UG. Once the child grows up and tried to

learn Japanese after the critical period, the child will face problems because the parameters for

English and Japanese are different and the child did not set the parameters for Japanese language

before puberty. Hence, it is clear that in this case, the CPH is again being supported.

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Arguments from Biological and Cognitivist Theories

The biological model is a school of thought that appears to come hand in hand with the

CPH. This model is most prominently proposed by Eric Lenneberg (1967) as well as Penfield

and Roberts (1959). In this model, the critical period of language acquisition is supported by

Penfield and Roberts as being under the age of 9. Lenneberg, on the other hand, began by

asserting that the critical period ended around the age of 4-5 (1964), before altering his view in

later on.

This change came about in part because of the focus on biological factor. Lenneberg

(1967) concluded that if no language is learnt by puberty, it cannot be learned in a normal,

functional sense, which is in agreement with the Problem Statement of this assignment. Puberty

(which is around the age of thirteen but varies between individuals) is said to coincide with the

phenomenon of brain lateralization (already explained earlier), where the brain loses its

plasticity, becoming rigid and fixed – with the left hemisphere fixed into language specialization.

The drawback of this is that the brain ostensibly loses its ability for extensive adaptation and

reorganization, rendering the learning of new languages much more difficult than before.

Evidence:

Intuitively, this appears to be accurate, but more proper evidence is seen from the cases

of deaf and feral children. Firstly, “feral children” are rare cases of children who are not exposed

to language during infancy or childhood due to being brought up in the wild, in isolation and/or

confinement. There are many scattered examples throughout recorded history, but two in

particular were studied and provided evidence for the Critical Period Hypothesis.

The first is ‘Genie’, who was deprived of social interaction by her mother until finally

discovered and rescued at the age of thirteen. She was completely without language and still

lacked linguistic competence even after 7 years of rehabilitation. She was able to acquire a

significant vocabulary, but was unable to string them to form grammatical sentences. Another

case is ‘Isabelle’, who was incarcerated with her deaf-mute mother until the age of six and a half.

She also started out with no language skills, but quickly acquired normal language abilities

through specialist training. Both children were similar in that they were deprived of normal

linguistic input but responded differently to rehabilitation. Their defining difference was in their

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age, as Genie was already thirteen while Isabelle was still pre-pubescent. This appears to support

the hypothesis that language input is necessary during the Critical Period for it to be learned in a

functional sense.

Problems with the evidence?

However, the evidence can be challenged on several grounds. Firstly, the isolation of

Genie could have produced general retardation and emotional trauma (unrelated to age) which

affects her ability to learn language. There is a possibility that Genie was of sub-par intelligence

due to her long period of isolation as well. Furthermore, the rehabilitation carried out for the two

feral children were different. Perhaps a different methodology might have worked for Genie.

However, Pinker (1994) supported Lenneberg’s ideas by citing the example of a 31 year

old deaf woman known as ‘Chelsea’ who was unable to acquire language early in life because

her deafness was only discovered much later. She was not abused mentally or physically as

Genie was, but upon the belated discovery of her deafness and the fitting of hearing devices, her

language acquisition took on a similar, agrammatical pattern as Genie’s (she was unable to grasp

syntax). Obviously, the lady was well beyond her supposed ‘Critical Period’.

Penfield and Roberts (1959) were also on the same track as they proposed that there are

neurological mechanisms behind the maturational change in language learning abilities. This

appears to explain why after a certain age (arbitrarily dubbed as the end of “the Critical Period),

language learning appears to be difficult, and absolute mastery of a new language and its

phonology in particular is extremely rare.

Nonetheless, these case studies are individuals; not a sufficient sample size for scientific

study. Furthermore, it goes without saying that we have to rely on these exceptional cases for

study since it would be extremely unethical to purposely “create” conditions of language

deprivation in people simply for research purposes.

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American Sign Language – Opposing Evidence?

To circumvent these methodological problems, there are studies of deaf children learning

American Sign Language (ASL) – which is in itself a bona fide language. Newport and Supalla

(1987) studied language acquisition in deaf children differing in age of exposure; few were

exposed to ASL from birth, though the majority learned it at school.

The results of this study challenged Lenneberg’s CPH since it showed a linear rather than

sudden drop in performance with increasing age of exposure. The late learners were exposed to

ASL at age four (far before the CPH ends) and yet were shown to do poorer than the earliest

learners. Hence, it is shown that language acquisition becomes harder as one becomes older, not

suddenly when the critical period ends. Furthermore, Krashen (1975) had the benefit of

reanalysing clinical data – showing that brain lateralisation happens much longer before puberty,

contrary to Lenneberg’s calculations. Hence, his biological basis for puberty being the end of the

Critical Period is shown not to hold water.

A linear rather than sudden drop in language acquisition in children is an idea that is in

sync with the cognitivist view, most famously proposed and developed by the psychologist Jean

Piaget (1926). Unlike the CPH, this view does not see language acquisition as distinct but simply

another part of general learning and intelligence, which continues to develop even into

adulthood. Intuitively, one is aware that even as an adult, journalists and writers continuously

refine and improve their skills at using the language. According to Huitt and Hummel (2003),

Piaget’s work also revealed that only 35% of high school graduates reach the “formal operational

stage” – which is the highest level of intelligence. This shows that many adults appear not to

think “formally”, as opposed to the CPH which purports that one should have attained mastery of

a language by puberty.

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Other possible explanations

There are several other factors that can account for the difficulties an individual faces in

learning a language besides being at an age over the critical period. One of these factors is

simply the brain’s aging. It cannot be argued that as a person ages, the brain’s capacity to

function as well as it used to be will decline. There will be certain age-related changes in a

person’s cognitive processing with the increase in age. Recent researches have found that the

effects caused from brain aging could be due to several reasons (Guttman, n.d.). These effects of

brain aging can range from age-related memory loss to severe conditions like Alzheimer’s and

dementia. On average, the brain loses 5-10 percent of its weight between the ages of 20 and 90.

What this mean is that people of a higher age tends to forget things easier thus causing

them to face more difficulties in learning something new compared to people of a lower age. Jeff

Victoroff, M.D., an associate professor of clinical neurology at the Keck School and director of

neurobehaviour at Rancho Los Amigos said that the reason our brains are declining with age

may be because in the evolution 100, 000 years ago, it was considered rare for people to live past

the age of 40 or 50 but because of technological advancement in medical research, this is no

longer a problem.

However, it also meant that there was little evolutionary selective pressure previously to

make the human brain work when we’re over 40. As a consequence, there will be a general

decline in the brain’s ability to process, remember and pay attention to things as an individual

grows older. These declines in the brain’s capability to function well will greatly affect the ease

of a person’s ability to learn a language.

Aside from that, there are also learner-related factors that one should consider in the role

of language learning. These factors are motivation, attitude and aptitude, and environment.

There is evidence that shows that when a person is highly motivated to learn a language;

the process will be smoother because the person is driven by the motivation to succeed in

learning the language. The motivation can be an extrinsic motivation or an intrinsic motivation.

Intrinsic motivation refers to a motivation guided by an internally rewarding effect like a sense

of fulfilment, competence and so on while extrinsic motivations refers to reward from outside

such as prizes, grades or other types of positive feedback (Brown, 2007). It is widely believed

that intrinsic motivation has a stronger bearing than extrinsic motivation in the long run but

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whatever the form of motivation may be, it can be safely said that should a person be motivated

to do so, learning a language may not be seen as a difficult task for the person.

The second learner-related factor is the attitude and aptitude of the person learning a

language. Attitude is how the learner views the language he or she is learning. If the opinion that

the learner has towards the language is positive then, no doubt the learner will be spurred on to

invest time and effort into learning the language.

Time, tutor, resources are some of the environmental factors that can affect a person’s

language learning process. An environment that is conducive will be able to optimise a person’s

ability for language learning. For example, if the tutor is unable to provide an effective teaching

style that matches the person’s leaning style the language learning process will become difficult

even if the person is at an age within the critical period. The same applies to resources and time.

If the resources are unsuitable and there is a time constraint, the person will be unable to learn a

language easily. It could be, then, that adults find it so difficult to learn languages because most

of our language teaching resources are tailored for and geared towards teaching younger students

and not mature ones.

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Conclusion

To conclude, the Critical Period Hypothesis (CPH) by Lenneberg hypothesise that there

is a crucial time frame for humans where experiences gained from the environment will have a

peak effect on development or learning which will result in a swift and easy process of acquiring

a language. This is made possible because before puberty, a child’s brain is still elastic and has

not been lateralised. Once the brain has been lateralised the elasticity will decrease thus causing

language acquisition to reach a flattening and learning a language during the period after puberty

becoming difficult.

Recent research has shown that the flattening of the peak effect (sudden drop) does not

happen but merely decline gradually as a person ages. This also proves that there is no well-

defined age for the crtitical period. Despite the fact that the ability of a person to learn a language

does not stop abruptly, age is still considered as a factor in language acquisition and learning.

This is due to some age-related changes in a human’s cognitive processing. Understandably, as

human ages, the ability to recall details, encode new information and so on will become impaired

and not as smooth as it used to be. These declines may account for the difficulty a person over

the critical age faces in learning a language.

While Noam Chomsky’s Innateness Hypothesis agrees with Lenneberg’s CPH that there

is a critical period in learning a language, there are several other linguists who do not think that

CPH exist for human’s ability to learn a language.

In conclusion, CPH is still a matter of extensive debate. Both biological and cognitivist

views support the idea of an innate source of language that activates upon exposure to the right

kind of language input – but their similarities end there. There is great debate when it comes to

the manner, timing and limit of language acquisition, while the sparse evidence that is available

are similarly debatable.

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Appendix

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