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His view of how children's minds work and develop has been enormously influential, particularly in educational theory. His particular insight was the role of maturation (simply growing up) in children's increasing capacity to understand their world: they cannot undertake certain tasks until they are psychologically mature enough to do so. His research has spawned a great deal more, much of which has undermined the detail of his own, but like many other original investigators, his importance comes from his overall vision.
He proposed that children's thinking does not develop entirely smoothly: instead, there are certain points at which it "takes off" and moves into completely new areas and capabilities. He saw these transitions as taking place at about 18 months, 7 years and 11 or 12 years. This has been taken to mean that before these ages children are not capable (no matter how bright) of understanding things in certain ways, and has been used as the basis for scheduling the school curriculum. Whether or not should be the case is a different matter.
Stages of Cognitive Development
Differentiates self from objects
Recognises self as agent of action and begins to act intentionally: e.g. pulls a string to set mobile in motion or shakes a rattle to make a noise
Achieves object permanence: realises that things continue to exist even when no longer present to the sense (pace Bishop Berkeley)
Learns to use language and to represent objects by images and words
Thinking is still egocentric: has difficulty taking the viewpoint of others
Classifies objects by a single feature: e.g. groups together all the red blocks regardless of shape or all the square blocks regardless of colour
Can think logically about objects and events
Achieves conservation of number (age 6), mass (age 7), and weight (age 9)
Classifies objects according to several features and can order them in series along a single dimension such as size.
(11 years and up)
Can think logically about abstract propositions and test hypotheses systemtically
Becomes concerned with the hypothetical, the future, and ideological problems
(Piaget, J., 1921)
The Language Acquisition Device (LAD) is a postulated "organ" of the brain that is supposed to function as a congenital device for learning symbolic language (i.e., language acquisition). First proposed by Noam Chomsky, the LAD concept is an instinctive mental capacity which enables an infant to acquire and produce language. It is component of the nativist theory of language. This theory asserts that humans are born with the instinct or "innate facility" for acquiring language. Chomsky has gradually abandoned the LAD in favour of a parameter-setting model of language acquisition (principles and parameters).
Chomsky motivated the LAD hypothesis by what he perceived as intractable complexity of language acquisition, citing the notion of "infinite use of finite means" proposed by Wilhelm von Humboldt. At the time it was conceived (1957-1965), the LAD concept was in strict contrast to B.F. Skinner's behavioral psychology which emphasized principles of learning theory such as classical and operant conditioning and imitation over biological predisposition. The interactionist theory of Jerome Bruner and Jean Piaget later emphasized the importance of the interaction between biological and social (nature and nurture) aspects of language acquisition.
Differing from the behaviorists who emphasize the importance of social interactions in language acquisition, Chomsky (1965) set out an innate language schema which provides the basis for the child's acquisition of a language. The acquisition process takes place in an infant's mind because of this mental organ which enables him/her to speak despite the limited nature of the Primary Linguistic Data (PLD, the input signals received) and the degenerate nature (frequent incorrect usage, utterances of partial sentences) of that data. Given this poverty of the stimulus, a language acquisition model requires a number of components. Firstly, the child must have a technique for representing input signals and, secondly, a way of representing structural information about them. Thirdly, there must be some initial delimitation of the class of possible language structure hypotheses. Fourthly, the child requires a method for determining what each of these hypotheses implies with respect to each sentence. Finally, an additional method is needed by which the child can select which hypothesis is compatible with the PLD.
Equipped with this endowment, first language learning is explained as performed by a Language Acquisition Device progressing through the following stages:
The device searches the class of language structure hypotheses and selects those compatible with input signals and structural information drawn from the PLD.
The device then tests the compatibility using the knowledge of implications of each hypothesis for the sentences.
One hypothesis or 'grammar' is selected as being compatible with the PLD.
This grammar provides the device with a method of interpreting sentences (by virtue of its capacity for internally representing structural information and applying the grammar to sentences).
Through this process the device constructs a theory of the language of which the PLD are a sample. Chomsky argues that in this way, the child comes to know a great deal more than she has 'learned', acquiring knowledge of language, which "goes far beyond the presented primary linguistic data and is in no sense an 'inductive generalization' from these data."
In some views of language acquisition, the LAD is thought to become unavailable after a certain age - the critical period hypothesis (i.e., is subject to maturational constraints). Feral children cases such as Genie provide key examples for the LAD aspect of the nativist theory and that it becomes unavailable after a certain age.
Learning theorists argue that the environments of young children everywhere are supportive of learning. All young children are surrounded by speech from the beginning: parents and others address remarks to babies, respond to their vocalizations and heap praise on their earliest attempts to say words. People adjust their own speech to accommodate the young child's needs, simplifying their vocabulary, shortening their sentences, and talking about the here-and-now, usually in a special speech "register." This motherese or parentese that cues the child that this is talk meant for the child's ears.
There are some theorists who argue that this environmental support gives the child everything necessary to "figure out" the rules of language. In other words, the child is like a miniature linguist, collecting evidence to decide among hypotheses about the grammar. But mathematical linguists have determined that any set of sentences is compatible with an infinite set of possible grammars. In 1968 a startling proof showed that human language is unlearnable in a finite amount of time: there are too many potential rule systems that could have generated the set of sentences a learner has heard at any one time.
One solution is to argue that the child receives accurate corrective feedback about his hypotheses. Under this kind of condition, language would be learnable in a finite time. But evidence for reliable and consistent corrective feedback in the average child's environment is very weak. When it comes to grammar, most parents notice only the superficial mistakes made by their children, and these only when the child is "old enough to know better," e.g., saying foots or comed when in grade school. Parents do provide some feedback about the clarity or truth of their children's sentences, but studies reveal that adults do not provide reliable feedback on the grammaticality of children's sentences. Explicit correction seems to be too rarely and inconsistently used to "train" the child to speak grammatically.
The alternative solution is to claim that the child has some preconceived ideas, or innate knowledge. Learning language is possible in a finite amount of time if the learner already knows the range of possibilities existing in universal grammar. Linguistic approaches to language acquisition assume that some knowledge about language is built into the human child.
Linguistic theory states that languages are deeply similar in ways that have only just begun to be uncovered. All languages seem to make use of the same small inventory of categories for the construction of sentences: noun phrases, verb phrases, sentences, and the like. In addition, there are principles that seem to be universal and which constrain the forms that sentences can take. Currently many people are persuaded that these facts might be part of the assumptions that the child brings to the language acquisition task. The child may in fact "know" that sentences are built from the abstract categories, and know in advance the principles that dictate that the rules are going to have a limited range of possible forms. These central ideas were introduced by Noam Chomsky in 1965 and have motivated much work on language development. Chomsky proposed that children are born with a Language Acquisition Device (LAD) that contains hypotheses that guide their language learning.
To demonstrate the subtlety of the abstract principles on which these arguments depend, consider the following short story:
Once there was a boy who loved climbing trees in the forest. One afternoon he slipped and fell to the ground. He picked himself up and went home. That night when he had a bath, he saw a big bruise on his arm. He said to his dad, "I must have hurt myself when I fell this afternoon."
Now comes the question:
a) When did the boy say he hurt himself?
Notice there are two possible answers, either to when he said it, or to when he hurt himself. That is, the "when" question could be connected to the "say" or to "hurt." Research shows that three-year-olds also allow both answers: sometimes giving one, sometimes the other. But now consider the subtle variant:
b) When did the boy say how he hurt himself?
Suddenly, the ambiguity is gone, and only one answer seems right: "that night in the bath." Three-year-olds also only give that answer to b). They seem to know already the constraint that question words may not "move" over another question word: a constraint that is embedded in universal grammar.
For a learning theory account to be viable, the two-year-old would have to have the ability to sift through evidence of this subtlety to arrive at the appropriate generalization. The problem that then arises is the rarity of such sentences. In hundreds of hours of recorded conversations between several young children and their caregivers , there are typically only a couple of dozen examples, and of course never the close contrasting pairs described above. It does not seem plausible that the child learns the contrasts for himself.
Instead, it is argued, the child is in possession of considerable pre-existing knowledge about the forms that rules can take. There is still considerable scope for learning theories. Even if the starting point is not a "blank slate" but a LAD, the child has to learn the meaning of every word in her language: no one has argued that words are innate! Furthermore, the child has to use the evidence of conversation to make a multitude of choices about the rules of her language (and their irregularities). The doctrine of innate ideas may have a relatively limited role to play except in defining the boundaries within which learning can take place.
Berko-Gleason, J. The Development of Language . New York: Macmillan, 1993.
de Villiers, P., and J. de Villiers. Early Language. The Developing Child series. Cambridge, Mass.: Harvard University Press, 1979.
Fletcher, P., and B. MacWhinney. The Handbook of Child Language. Cambridge, Mass.:Blackwell Publishers, 1995.
Goodluck, H. Language Acquisition: A Linguistic Introduction. Cambridge, Mass.: Blackwell Publishers, 1991.
Pinker, S. The Language Instinct. New York: Morrow, 1994.
Jill De Villiers, Ph.D. Smith College "Language Acquisition Device (LAD)". Encyclopedia of Childhood and Adolescence. FindArticles.com. 06 Apr, 2011.