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Language Acquisition Device (LAD)

The Language Acquisition Device is a theoretical brain module proposed by Noam Chomsky in the 1950s. This concept was developed to explain how humans learn complex grammatical rules of language. Communication is fundamental to the human way of life. By understanding how we use language for communication we can better understand how to help children develop their communication skills. The concept of a language acquisition device is consistent with the natavist theory. It proposes that humans are born with an innate predisposition to learn language. The brain is structured at birth in such a way that it is receptive to the sounds of language. This is what allows children to learn language at such an accelerated rate This theory was very controversial at the time it was developed because it went against the behaviorist views of language that were dominant at that time. The theory's ideals are in direct opposition to the empiricist approach to language. The empiricist approach argues that children learn the rules of grammar based on negative reinforcement from other language speakers. Proponents of the LAD theory argue that children do not receive enough negative evidence to account for the rate of language development and therefore a LAD must exist. The concept of universal grammar stems off of the belief that a language acquisition device exists in the brain. The LAD is important to the field of cognitive science in that it caused a great deal of controversy among researchers. The controversy helped to fuel the research of both innate language as well as ideas about how language is learned.

=History=

The idea of a language acquisition device was first proposed by Noam Chomsky in 1965 with the publication of his book, Aspects of the Theory of Syntax. This book expanded on his previous book, Syntactic Structures. Chomsky's idea of a LAD was highly controversial in that it challenged the existing behaviorist ideas of the time. Behaviorism viewed language as stemming from children's imitation and reinforcement of what they hear. B.F. Skinner was a major behaviorist researcher during the 1950s who contested Chomsky's ideas. Skinner wrote the book Verbal Behavior in 1957 which outlined his view of how children learn language through operant conditioning. Skinner believed that children learned language through a set of grammar rules that they used to help them produce sentences. If they produced incorrect sentences, their behavior would be negatively reinforced through the negative social responses of others. Chomsky later wrote a review of Skinner's book which highly criticized many of Skinner's fundamental ideas of verbal behavior. The disagreements between Chomsky and Skinner led to the Linguistic Wars. These public debate between the two researchers led to an increase in interest in linguistic research. Since then there has been an explosion of research in the field of linguistics. The nature nurture debate of language has continued with ongoing research on how children learn and develop language.

=What is the Language Acquisition Device?=

The Language Acquisition Device refers to a proposed innate human ability to understand and construct language. The nativist perspective on language proposes the poverty of the stimulus argument, that it would be impossible for children to learn language at the rate that they do without some innate predisposition to learning language. There is simply not enough language input during early childhood to account for the massive amount of language that children learn within the first few years of their lives. A human's brain must be set up to be receptive to language input before it is born. This innate "Language Acquisition Device" allows an infant to be receptive to language input.

Children do learn language with a limited amount of input.The amount of grammatical information given to children is not enough to account for the speed at which they learn grammar rules. By 18 months infants have already developed syntactic knowledge. Researchers argue that the amount of grammatical knowledge that an 18 month old has acquired cannot have come simply from adult grammatical input. There must be something more involved in the language acquisition process.

Natvist's argue that children try out different various linguistic options that are available to help them determine grammar rules however children only try out options that are consistent with the rules of universal grammar. Children must have an innate universal grammar in order to differentiate which options are plausible. This innate universal grammar is built out of the language acquisition device.

Universal Grammar
Chomsky supports the theory of a language acquisition device through his work on universal grammar. Universal grammar stems from the idea that the ability to learn grammar is an innate aspect of the brain. There are properties that all human languages share. Because these properties are shared across all languages, it is thought that these properties as hard wired into the human brain. Even with different types of language input the brain is able to learn grammatical rules seemingly without too much difficulty. This argument is supported by research showing that infants interpret words within a sentence better than they do in isolation. It seems that infants have an innate predisposition to understand language better when it follows grammatical rules that are consistent with their universal grammar rules.

Familial Language Impairment
Research done on familial language impairment seems to support the idea of a genetic component to language. Families, such as the KE family, are characterized by language deficits affecting half of all family members. In the case of the KE family a specific chromosomal mutation was identified as being the cause of this language disorder. Another known familial language impairment includes a family in which over half of them had trouble producing the proper tense in language. The presence of familial language impairments indicates that there is some sort of gene that codes for language development. When this gene is compromised there is a deficit in one area of language or another. This supports the idea that there is a part of the brain that is hardwired for language. In theory if the language acquisition device is passed down through generations then damage to that device would result in language deficits, which is exactly what is seen in familial language impairments. Proponents of a language acquisition device would argue that these specific families have problems learning grammatical rules because of a mutation in the part of the brain that codes for a language acquisition device.

=Criticisms=

The Nature Nurture Debate
The nature nurture debate is highly debated in many areas of science. The nature side of the debate argues for innate predispositions for learning specific human tasks. It relies on the evolutionary perspective to account for how humans developed these abilities. In the context of language acquisition the nature side of the debate relies on concepts such as a language acquisition device and universal grammar. The nurture side of the debate looks at the acquisition of language from an empiricist perspective. Researchers such as John Locke believe that children are born with tabula rasa or blank slate. Everything that a human is capable of doing is a learned process. The idea of a language acquisition device runs in direct opposition to the nurture view of language acquisition. The theory of a LAD is criticized for the lack of focus on the importance of exposure to language during critical periods. According to researchers who take an empiricist approach to language, an infant learns language through exposure to language during critical periods of development. Without proper exposure to language it is difficult, if not impossible, to teach a person how to communicate through language. Empiricist argue that language is a learned skill. Children learn language through imitation of other language speakers. This theory is reinforced from evidence collected from feral children. The case of Gene (feral child) illustrates how a child without proper language input during critical periods may never fully learn language. The case of Victor of Aveyron has also been used to illustrate the empiricist view. There is however debates about whether the children in these two cases had other cognitive deficits that could have hindered their language ability. It would be unethical to replicate this in an experimental study to learn any more information on this.

The empiricist view was shaped by B.F. Skinner. Skinner was a behaviorist. He believed that language could be learned just like other cognitive behaviors, through reinforcement and shaping. Positive reinforcement occurs when the child is exposed to language that follows grammatical rules. Negative reinforcement occurs when the child makes a mistake and the parent corrects the child. This view is strongly opposed by the nativist theory of language. A nativist would argue that a parent is more concerned with the content of a child's utterances. Parents respond to grammatically incorrect sentences and therefore the child may not be exposed to the negative evidence that would be needed for this type of learning to occur.

Some empiricists also criticize the the poverty of stimulus argument, a central claim of the nativist approach, which claims that language cannot be learned as fast as it is without some sort of innate ability to learn language. Some researchers argue that since language input occurs over the course of several months, children do actually have the time to learn these abilities. These seemingly innate abilities to process language are actually learned skills.

Neuroimaging Studies
Modern medical imaging techniques are coming closer to understanding the human brain, but researchers are still learning new things about the complexities of the human brain. Neuroimaging studies tend to support the nurture side of language acquisition. Brain growth correlates with increases in language ability in early childhood. As the level of language increases, so too does the size and connectivity of brain areas thought to be important for language. Empiricists use this correlation to argue in favor of the idea that language is a learned process.

Connectionist Models
Connectionist models of language acquisition strive to imitate human language acquisition. Although researchers are coming close to developing models that are similar to human cognition there is still some work to be done in this area. The connectionist models seem to be biologically plausible and therefore have helped fuel research ideas in the area of learning language. These models support the nurture approach to language in that language can be taught through experience. A nativist argument would critique this model because it still does not account for poverty of stimulus. An infant would not receive the amount of input that is given to a model.

Rationalism
Many modern researchers have criticized Noam Chomsky's language acquisition approach to language as being too rationalist. The theory was not developed through the rigorous systematic observation that is expected of studies employing the scientific method. Even with the technology we have today it is difficult to support the claim that such a language acquisition device truly does exist. Although it is hard to try to prove this theory, it is also almost impossible to disprove this theory. Language acquisition is such a natural human process that it becomes hard to break down exactly how much comes from an innate system and how much comes from the learning process. Since infants are unable to tell us what they do know at birth, the way language is learned must be inferred through studies that indirectly study language acquisition. Many researchers have begun to study the process of language development from the perspective that both nature and nurture may be involved in the language acquisition process.

=New Directions in Theories of Language Acquisition=

Although many researchers have argued strongly for each side of the language acquisition argument, it is more likely that language acquisition is a combination of both nature and nurture. Humans need both a brain that is set up to be receptive to language as well as language input during critical periods in their lives. If either of these components are lacking then that person will not develop full language capabilities. Research continues to investigate language through the use of neurological techniques. As researchers begin to understand the way in which the mind words they come closer to understanding how language works within the mind. The application of applied research on how the brain works in relation to language is gaining more interest.

One application of research on language areas of the brain is assisting teachers in the education system in understanding the developmental cognitive level of their students. By understanding exactly how a child learns language a teacher may be able to target certain deficits during critical periods of language development before they become a problem.

=See Also= Linguistics

Universal Grammar

Poverty of the stimulus

Nature versus Nurture

Principles and Parameters

Noam Chomsky

B.F. Skinner

Linguistic Wars

=References=