The Critical Period Hypothesis: Where Are We Now?
Harley and Wang
The Critical Period Concept
• Period of time during the life cycle when there is greater sensitivity to certain
stimuli than at other times
• Ex: filial imprinting in birds. Limited period after hatching, goslings become
irreversibly attached to the first moving object they see
• ‘Sensitive period’ now used instead of ‘critical period’, pointing to the more
gradual nature of development
• Colombo says a critical period must have:
o An onset
o A terminus
o An intrinsic (maturational) component
o An extrinsic component in the shape of a stimulus to which the organism
o A system that is affected by stimulation during the critical period
• Ultimate and proximate causes of critical period phenomena:
o Ultimate causes have to do with the functions and benefits of the critical
o Proximate causes are concerned with the mechanisms that regulate the
growth and decline of sensitivity.
Lenneberg’s Critical Period Hypothesis
• The onset: marked by a peculiar, language-specific maturational schedule
consisting of gradual unfolding of capacities between the 2 and 3 years of life.
Lack of language before 2 due to cerebral immaturity, rather than immaturity of
• The terminus: age 13, or puberty. See a rapid decline in language acquisition
capabilities, coinciding with the completion of lateralization of language function
to the dominant left cerebral hemisphere. 2 language learning becomes different,
less natural than learning a language during the critical period. Adults are able to
learn a 2 language because languages resemble one another, and a cerebral
matrix for language skills exists.
• The intrinsic component: the child is endowed from the outset with an innate
mechanism dedicated to language. Argued for understanding neurological
correlates of language in terms of the way many parts of the brain interact, not
specific brain structures.
• The extrinsic component: recognized that environmental influences on language
acquisition were undeniable, but wasn’t interested in elaborating on this aspect.
• The affected system: referred mostly to ‘language’ without specifying what
particular aspects (e.g. phonology, syntax). Emphasized capability in contrast to
behaviour (similar to Chomsky’s competence compared to actual performance • Ultimate causes: human language is a social adaptation contributing to the
survival of the species. Variation at the surface structure level of language is
permissible, but very little tolerance for abnormality in the deep structure.
The Empirical Evidence
• One argument is that there is no particular maturational stage where language
acquisition emerges, but the process begins at birth and continues on throughout
• There is tentative support from speech perception research for some kind of innate
mechanism for language acquisition. Whether operational from birth or emerges
during infancy is unclear.
• When exposure to language is substantially delayed, ultimate attainment is
irregular and incomplete. Cannot compensate for initial deprivation.
• Congenitally deaf adults exposed to ASL at different ages: clear age-related effect
for morphology, native-learners outscoring early learners, early learners
outscoring late learners.
• Later second language learning of ASL was enhanced by having previously had
full access to a first language, but also native language experience in infancy/early
childhood was still better than second language learning later on
• Rate-of-acquisition studies have shown adults and adolescents generally making
faster initial progress than children, older children progressing faster than younger
children. These advantages can be short-lived, and little to no difference seen
between adjacent age groups.
• Studies of long-term attainment ind2 language pronunciation indicate the
younger the age of arrival in a 2 language environment, the better the
pronunciation will be. Age of arrival in the environment is key predictor, rather
than length of residence (which is important only for the first few months after