In his seminal book Biological Foundations of Lan- guage, Eric Lenneberg hypothesized that human language acquisition was an example of biologically constrained learning, and that it was normally acquired during a critical period, beginning early in life and ending at puberty. The critical period hypothesis was first proposed by Montreal neurologist Wilder Penfield and co-author Lamar Roberts in their book Speech and Brain Mechanisms, and was popularized by Eric Lenneberg in with Biological Foundations of Language. First-language acquisition relies on neuroplasticity.History · Experimental and · Effects of aging · Deaf and feral children. Lenneberg, E.H. Biological Foundations of Language. Wiley, N.Y.
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Critical period hypothesis
History[ edit ] The critical period hypothesis was first proposed by Montreal neurologist Wilder Penfield and co-author Lamar Roberts in their book Speech and Brain Mechanisms,  and was popularized by Eric Lenneberg lenneberg 1967 with Biological Foundations of Language.
First-language acquisition relies on neuroplasticity. If language acquisition does not occur by puberty, some aspects of language can be learned but full mastery cannot lenneberg 1967 achieved. Lenneberg 1967 speaking, the experimentally verified critical period relates to a time span during which damage to the development of the visual system can occur, for example if animals are deprived of the necessary binocular input for developing stereopsis.
Critical period hypothesis - Wikipedia
It has however been considered "likely",  and has lenneberg 1967 many cases been flatly presented as fact, that experimental evidence would point to a comparable critical period also for recovery of such development and treatment; however this is a hypothesis.
Recently, doubts have arisen concerning lenneberg 1967 validity of this critical period hypothesis with regard to visual development, in particular since the time it became known that neuroscientist Susan R.
Barry and others have achieved stereopsis as adults, long after the supposed critical period for acquiring lenneberg 1967 skill. This pattern of prefrontal development is unique to humans among similar mammalian and primate species, and may explain why humans—and not chimpanzees—are so adept at learning language.
Certainly, older learners of a second language rarely achieve the native-like fluency that younger learners display, despite often progressing faster than children in the initial stages. For example, adult second-language learners nearly always retain an immediately identifiable foreign accent, including some who display perfect lenneberg 1967.
Adults learning a new language are unlikely to attain a convincing native accent since they are past the prime age of learning new neuromuscular functions, and therefore pronunciations. Writers have suggested a younger critical age for learning phonology than for morphemes and syntax.
The plasticity of procedural memory is argued to decline after the age of 5. The attrition lenneberg 1967 procedural memory plasticity inhibits the ability of an L2 user to speak their second language automatically.
It can still lenneberg 1967 conscious effort even if they are exposed to the second language lenneberg 1967 early as age 3. This effort is observed by measuring brain activity. L2-users that are exposed to their second language at an early age and are everyday users show lower levels of brain activity when using their L1 than when using their L2.
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This suggests that additional resources are recruited when speaking lenneberg 1967 L2 and it lenneberg 1967 therefore a more strenuous process. The critical period hypothesis in SLA follows a "use it then lose it" approach, which dictates that as a person ages, excess neural circuitry used during L1 learning is essentially broken down.
The structures necessary for L1 use are kept.
On the other hand, a second "use it or lose it" approach dictates that if an L2 user begins lenneberg 1967 learn at an early age and continues on through his life, then his language-learning circuitry should remain active. This approach is also called lenneberg 1967 "exercise hypothesis".
For instance, if an SLA researcher is studying L2 phonological development, they will likely conclude that the critical period ends at around age 3. If another SLA researcher is studying L2 syntactical development, they may conclude that the critical period ends at a much later age.
These differences in research focus are what create the critical period timing debate. Some writers have argued that the critical period hypothesis does not apply to SLA, and that second-language proficiency is determined by the time and effort put lenneberg 1967 the learning process, and not the learner's age.
A combination lenneberg 1967 these factors often leads to individual variation in second-language acquisition experiences. Lenneberg 1967 evidence for L2 learning ability declining with age is controversial, a common notion is that children learn L2s easily, whilst older learners rarely achieve fluency.
A CP was popularised by Eric Lenneberg in for L1 acquisition, but considerable interest lenneberg 1967 surrounds age effects on second-language acquisition SLA. SLA theories explain learning processes and suggest causal factors for a possible CP for second language acquisition.
These SLA-CP theories mainly attempt to explain apparent differences in language aptitudes of children and adults by distinct learning routes, and clarify these differences by discussing lenneberg 1967 mechanisms.
Research explores these ideas and hypotheses, but results are varied: Mayberry and Lock, have recognised certain aspects of Lenneberg 1967 may be affected by age, whilst others remain intact.
lenneberg 1967 The objective of this study is to investigate whether capacity lenneberg 1967 vocabulary acquisition decreases with age. Other work has challenged the biological approach; Krashen re-analysed clinical data used as evidence and concluded cerebral specialisation occurs much earlier than Lenneberg calculated.