The critical period
Problems within UG theory for L2 acquisition[ edit ] There are, however, problems with the extrapolation of the UG theory to SLA: L2 learners go through several phases of types of utterance that are not similar to their L1 or the L2 they hear.
The process occurs through receptors, second messengers, genes and protein synthesis.
Newborns of these species have a very limited array of innate survival abilities. A more general problem is that, as Pinker notes, almost every sentence anybody voices is an original combination of words, never previously uttered, therefore a language cannot consist only of word combinations learned through repetition and conditioning; the brain must contain innate means of creating endless amounts of grammatical sentences from a limited vocabulary.
According to Pinker, language must be viewed as a concept rather than a specific language because the sounds, grammar, meaning, vocabulary, and social norms play an important role in the acquisition of language.
The critical period
Hopkins, B. It is most difficult in stimulus deprivation and strabismus, less difficult in anisometropia, and not too difficult in astigmatism. The plasticity of procedural memory is argued to decline after the age of 5. This did not happen to adult cats even when one eye was sewn shut for a year because they had fully developed their vision during their critical period. Some, however, consider the possibility of the critical period or a critical period for a specific language area, e. Therefore, the critical period is an adaptive mechanism that keeps these pressures at equilibrium, and aims at optimal reproductive success for the individual. This model was important because it was able to describe a strong critical period for the proper development of normal ocular dominance columns in the lateral geniculate nucleus , and thus able to explain the effects of monocular deprivation during this critical period.
There are a number of factors that are more abundant or more active during the critical period. Her case presented an ideal opportunity to test the theory that a nurturing environment could somehow make up for the total lack of language past the age of They found that mice that were exposed to an abnormal auditory environment during a critical period P P15 had an atypical tonotopic map in the primary auditory cortex.
Critical period for second language acquisition
Most researchers agree that a cp is most likely to constrain the acquisition of pronunciation and grammar and, consequently, these are the areas primarily looked into in studies on the cph . On the other hand, a second "use it or lose it" approach dictates that if an L2 user begins to learn at an early age and continues on through his life, then his language-learning circuitry should remain active. They found the most activated brain areas during the tasks were not those generally associated with language, but rather those related to mapping orthography to phonology. SLA theories explain learning processes and suggest causal factors for a possible CP for second language acquisition. Pheromones play a key role in the imprinting process, they trigger a biochemical response in the recipient, leading to a confirmed identification in the other individual. Later experiments in monkeys found similar results consistent with the strong critical period. They found that native-English speakers who learned German as adults were disadvantaged on certain grammatical tasks but performed at near-native levels on lexical tasks. While psychologists and ethologists that is, biologists who study the natural behavior of animals have long recognized that early postnatal or posthatching life is a period of special sensitivity to environmental influences, their studies of critical periods focused on behavior. Human newborns are among the most helpless known with orangutang newborns ranking second. This has been useful in evaluating factors that are related to susceptibility, alias plasticity, and distinguishing them from factors that simply increase or decrease with age, and are affected by dark-rearing in the same way at all ages.
Expression of the protein Lynx1 has been associated with the normal end of the critical period for synaptic plasticity in the visual system. It is most difficult in stimulus deprivation and strabismus, less difficult in anisometropia, and not too difficult in astigmatism.
Critical and sensitive periods of child development examples
To elaborate, the behavioural outcome, i. The good news is that, unlike in the case of first language acquisition, the hypothesis is testable for second language acquisition. Studies have found that during critical periods in the visual cortex, neural synapses become the target of microglial phagocytosis. Does the critical period constrain implicit learning processes only, i. If language acquisition does not occur by puberty, some aspects of language can be learned but full mastery cannot be achieved. Some studies e. In a related study, Barkat, Polley and Hensch looked at how exposure to different sound frequencies influences the development of the tonotopic map in the primary auditory cortex and the ventral medical geniculate body. Writers have suggested a younger critical age for learning phonology than for morphemes and syntax. Early in development, most of the visual cortex is binocular, meaning it receives roughly equal input from both eyes. In fact, research indicates that age effects of all kinds depend largely on the actual opportunities for learning which are available within overall contexts of L2 acquisition and particular learning situations, notably the extent to which initial exposure is substantial and sustained Lightbown
The two most famous cases of children who failed to acquire language after the critical period are Genie and the feral child Victor of Aveyron.
Reprinted with permission from Daw The other is known as the M pathway, and goes through the magnocellular layers of the lateral geniculate nucleus to layer IVCalpha in striate cortex, leading to layer IVB, V2, MT, and dorsal areas in the parietal cortex.
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