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Critical Period Hypothesis
Terms and Concepts
A critical period: a time during an organism’s life span when it is more sensitive to
environmental influences or stimulation than at other times during its life.
•Critical period:
- begins and ends abruptly
- period beyond which a phenomenon will not appear
•Sensitive period:
- begins and ends gradually
- period of maximal sensitivity
•Window of opportunity:
- popular metaphor
- introduced by P. Bateson, 1978 in his critique
•Questions:
- How long does the critical period last?
- When does the plasticity of the brain come to an end?
Lenneberg's (1967) Critical Period Hypothesis

Lenneberg theorized that the acquisition of language is an innate process
determined by biological factors which limit the critical period for acquisition of a
language from roughly two years of age to puberty.

Lenneberg believed that after lateralization (a process by which the two sides of
the brain develop specialized functions), the brain loses plasticity.

Lenneberg claimed that lateralization of the language function is normally
completed at puberty, making post adolescent language acquisition difficult.
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Studied Scenarios of
the Critical Period
Those who believe in it say….
Children's brains were able to recover from this
much faster than an adult with the same injuries.
Childhood Aphasia (an
Because the brain heals so quickly when young,
injury to the brain)
this must be the critical period for learning
language.
Those who DON'T believe in it argue…
More rapid recovery in children is due to
the fact that a different side of the brain
took over the function in a child; adults'
brains are already fully developed so this
isn't possible.
Second Language
Acquisition
Long term mastery of a second language
decreases as age increases. Because children can
pick up a second language faster, this must be
because they are still in their critical period.
Second language acquisition doesn't
necessarily have anything to do with first
language acquisition. Just because one can
acquire a second language faster does not
mean he couldn't acquire it outside of his
critical period.
Deaf children with
hearing parents
The older a child is when he starts learning sign
language, the harder of a time he has acquiring
it. This must mean that he has missed his critical
period for learning language.
Studies find that these children do
eventually acquire sign language
proficiency although it does take longer to
learn. This refutes the critical period
hypothesis saying that one can learn
language at any age.
Cases of Childhood
extreme deprivation
If the child was rescued before the age of 7,
much greater gains were made in acquiring
language. This must be because a child is still in
his critical period before the age of 7.
It is not certain if children in cases of
extreme deprivation have trouble learning
language because they have missed their
so-called "critical period" or if it is because
of the extreme trauma they have
experienced.
Feral Children
•See the classroom handout
•Questions:
- Look at the ages at which the children were first exposed to
language. Do you think the evidence supports the idea of a
critical period? If so, at what age do you think it ends?
- Do you think researchers should consider other factors besides
age in studying delayed language acquisition? If so, what are
they?
•David Skuse (1993) draws the following conclusions from the language deprivation data:
- In adverse childhood circumstances, language seems more
vulnerable than other cognitive faculties.
- In cases of deprivation, speech appears to be more retarted than
comprehension. It develops more slowly after discovery.
- Interpersonal contact makes an important contribution to the
speed and success of late language development
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Genie: A study of a young girl who was deprived of language in her early years
BACKGROUND
• Her parents had abused her and kept her locked up for most of her 13 years until she was
discovered.
• She had been kept in a small room tied to her potty chair.
• She was not allowed to speak or make sounds.
• She was only given baby food and cereal to eat.
• She had been to the doctor one time in her childhood and there was no sign or retardation
in her first 3 years of life.
• When she was admitted to the hospital in November of 1970, she was 54 inches tall and
weighed only 62 pounds.
• She could not stand, chew solid food, and couldn't make sounds.
RESULTS OF TESTS ON GENIE
• At first, Genie was unwilling to cooperate. Researchers had to wait 11 months to run tests
therefore making it hard to truly assess Genie's linguistic capabilities.
• At first, it was clear Genie could understand more than she was able to speak.
• Slowly, over 2 years, she began to understand more and more.
• She finally picked up the difference between singular and plural nouns, negative and
positive sentence distinctions, possessive constructions, a few prepositions, and some
modifications.
CONCLUSIONS BASED ON TESTS RUN
ON GENIE CONCERNING THE CRITICAL PERIOD HYPOTHESIS
• It is unclear if her inability to learn was due to the fact that she had missed her critical
period, or the fact that she had undergone extreme trauma as a child.
• It is also hard to assess this case because researchers weren't able to test her immediately
upon discovery to really get a grasp for her language acquisition skills early on. They had
to wait until she was ready to cooperate. In that window, Genie could have picked up
more language or less than was accounted for.
Critical Period hypothesis and the SLA
The hypothesis is:
-
-
That the plasticity of the brain permits younger learners to
acquire a second language much more successfully than adult
ones;
That the universal grammar which permits us to acquire our fist
language is no longer available after a certain age.
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An influential study by Johnson and Newport (1989) reported results highly consistent with
the critical period hypothesis. The study is widely cited as authoritative evidence for a
critical period in L2 acquisition. In their study of native speakers of Chinese and Korean
who came to the United States at ages ranging from 3 to 39 years old, they asked subjects
to identify grammatical and ungrammatical sentences that were presented in the auditory
mode. The 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 (satisfying Conditions 1 and 2); in
addition, the adult learners showed great variability in learning outcomes whereas the child
learners did not (Condition 4).
A minute paper:
The Critical Period Hypothesis for learning a first language and the reasons I believe and
don't believe in it.