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This essay will deal with three theories of language acquisition: the linguistic theory, behaviourist theory and social interactionist theory. Each theory will include an explanation of the theory, a look at whether it is nativist or empirical, whether the evidence is more focused on competence or performance, the evidence supporting and criticising the theories and examples of how the theories apply to the areas of speech and language therapy will also be looked at.
The concept of a language faculty was first proposed by Noam Chomsky in 1976 and suggested that humans have an innate knowledge of grammar which has two levels of linguistic processing; deep structure and surface structure. Level one incorporates phrase structure rules which are the basic relationships underlying all sentence organisation in all languages. Level two incorporates transformational rules that govern the rearrangement of the phrase structure rules based on a specific structure. He suggested that humans have a language acquisition device -replaced by Universal Grammar in his later work- that allows us to create symbols and organise communicative expressions. Harley (2008). He argues that it is acquired at a time when the child's intellectual capabilities are not yet developed and therefore cannot be dependent on cognition. Harley (2008) Recently Chomsky has revised some of his previous claims and his more recent approaches are the Minimalist Program and the Principles and Parameters theory.
Chomsky refers to the idea of parameter setting to explain the acquisition of different languages, that exposure to a specific language is constrained by switches that are set off within a certain environment. Harley (2008). An example of a parameter setting is whether a language is pro-drop or not. If a child is exposed to a pro-drop language such as Italian or Spanish they automatically know that they are allowed to drop the pronoun, whereas an English language learner will have the parameter setting at non-pro-drop, and keep the pronoun. According to Chomsky, as cited in Harley (2008) the language faculty should involve a cognitive system that holds information, and a performance system that can use this information.
Competence-which is a person's knowledge of language involving the rules of grammar-, is favoured over performance within linguistic theory. The focus of language learning in linguistic theory is on the child. Unlike in behaviourism, the environment does not shape or train verbal behaviour. Berko Gleason (2005). Nativists follow the idea that language is much too complex a process to learn and that it is learnt at such a fast rate, that it would be impossible for it not to be innate.
Lenneberg's critical period hypothesis states that language development occurs during a critical period of a child's life and that certain linguistic events must take place in order for it to progress. Harley (2008). However, evidence from second language acquisition research shows that this can be true for phonological and syntactic development, but research has shown that it is not a perfect test of the critical theory hypothesis overall, as second language learners will have already acquired a first language. Harley (2008).
Supporting evidence cross-linguistically shows that regardless of the word order of a language, subject-object order is followed by children, which proves the existence of a language acquisition device universally. Berko Gleason (2005). If children are deprived of linguistic input during the critical period, studies have shown they are unable to acquire language normally, as is the case with "Genie". Genie was a normal child who suffered extreme abuse in her home and spent most of her time tied up in isolation, so she was unexposed to speech from a young age. Because of this abuse, she was deprived physically and socially and her linguistic skills were undeveloped. When she was taken into care at almost 14 years of age, Genie was taught language but she never reached full fluency. She learned certain syntactic structures but her case proves that a limited amount of language can be learnt once the critical period has been passed. Harley (2008)
Contrary evidence claims that just language alone is not sufficient to acquire language, that input is necessary and that the influence of environmental factors cannot be ignored. Pinker's (1984) poverty of stimulus idea offers that just because someone cannot imagine how a particular behaviour might have been learned, it does not mean it was not learned. Berko Gleason (2005) Chomsky does not focus on the link between syntax and semantics though he does refer to it in his book 'Syntactic structures' with the quote "colourless green ideas sleep furiously" which shows an example of a syntactically correct sentence lacking meaning.
In terms of how linguistic theory applies to the area of speech and language therapy, an explanation of aphasia and agrammatism is necessary. Aphasia is a language disorder that results from brain damage caused by disease, stroke or brain trauma. The main characteristics of one type of aphasia, Broca's, are; the speech being telegraphic, which means that articles, conjunctions, prepositions, auxiliary verbs and pronouns and morphological inflections are omitted. Agrammatism is a feature of Broca´s aphasia and the various linguistic theories that deal with agrammatism are; trace deletion hypothesis, theta assigning principle, double dependency hypothesis and tree pruning hypothesis. Edwards (2005).One of these theories, the tree pruning hypothesis, is an example of how the syntax of a language can be affected. The impairment occurs on the highest nodes of the syntactic tree and in English, this means that Wh questions and yes/no questions are affected, although in other languages, it can vary. The impairments are in word order, in embedded clauses and inflection for tense. Edwards (2005). While a syntactic explanation for language impairments in Broca´s aphasia and agrammatism can show what needs to be worked on in therapy, the exact nature of the deficits are different depending on whether it is a production or comprehension deficit so the speech and language therapy case management plan would have to be modified depending on which one it is.
In contrast to the linguistic emphasis on language use, the behavioural emphasis was mainly developed by the psychologist BF Skinner in his book 'Verbal Behaviour' (1957).His basic premise is that children learn to talk because of imitation and reinforcement.
Despite many variants of hypotheses concerning behaviourism, most theories consist of the idea that language is a subset of a behaviour which is learned through connections between a stimulus and a response. Owens (2008). They agree that there are some internal connections with language learning in the brain yet disagree with the idea of specific internal structures and suggest further research is necessary to understand the processes. Berko Gleason (2005)
In comparison to linguistic theory where the focus is on competence, performance is highlighted more in behaviourism. Skinner (1957) described language as being something we do and that it is a learned behaviour like any other skill. Contrary to nativists, he claimed that syntactic forms were not important and defined language as verbal behaviour since a child is unable to create a rule and thus shaped by external stimuli (parents).
The idea that language is a learnt behaviour opposes that of nativism. Skinner (1957) claimed that parental reinforcement allows a child to acquire language and that it is a process of imitation that a child must work at. In this model, children are seen as passive recipients of language training and it is suggested by Skinner that the child has no active role in acquisition. According to Whitehurst and Novak (1973) after a lot of trial-and-error modelling the adult role-models in the environment-by shaping and imitation training-reinforcement and punishment will improve children's speech output. An example of this reinforcement is soothing or attending to the child when they produce correct speech sounds. It is said that with enough sound samples, the child will learn a word association pattern rather than rules of grammar. Owens (2008). What is suggested is that language behaviour is shaped by the environment and not governed by rules or maturation, unlike in Chomsky's generativist approach.
Supporting evidence for behaviourism include studies of both disordered and normal children. Since Skinner's research, environmental input is considered an essential part of the acquisition of language, despite Chomsky's conclusion that Skinner's work was premature. Owens (2008). Lovaas's (1977) advancement with behavioural modification of children with autism has shown that techniques such as shaping and reinforcement assist children with restricted speech abilities. It should be noted that despite this discovery, it is unclear how the acquisition process differs between normal and disordered children. In a 1968 study by Palermo and Eberhart, adults were shown to follow the same learning patterns as children, when they were taught an artificial language.
Evidence against behaviourism shows that while lab studies on adults show positive results, they do not provide a full explanation on how children acquire language since they are not done in a child's environment. Adults also provide a poor model of imitation as their grammar is full of errors, dialects and slang. What this shows is that children do not copy parents because how could they select correct speech over erroneous speech? Additionally, research by Brown and Hanlon from 1970 shows that children are not punished or rewarded for using certain utterances and the main focus of correction or reward is more on the semantics than the syntax. What this shows is that in behaviourism, input is focused on excessively and is inadequate at explaining the full gamut of what is required to learn a language. Berko Gleason (2005)
As previously mentioned, behaviourism has been useful in speech and language therapy in the area of autism. With the Picture Exchange Communication System (PECS), communication for children with autism can be vastly improved and act as an aid in devising strategies for solving issues and improving the standard of living for people.
The interactionist approach puts forward the idea that a variety of factors influence the language development of a child, while using a mix of the linguistic and behavioural approaches. There are three different approaches concerning interactionism; Piaget's cognitive theory, information processing and the social interactionist theory. Piaget's interactive approach focuses on constructivism, which is the idea that linguistic structures are the emergent properties of language. His idea that children's processes are essentially different to adults would also have an effect on language acquisition. The second approach sees cognition as being computational, deriving patterns from data while assuming the mind as a type of software and the brain as hardware. The third approach is one that will be focused on here and it concerns the social interactionist theory.
According to Vygotsky (1962) cognitive and social factors can influence the development of language acquisition, which in turn can have a reciprocal influence on cognition and social abilities. Social interactionists believe that children influence their parents in their acquisition of language and that they and the language environment work together as a dynamic system. Berko Gleason (2005)
In terms of competence and performance, interactionists need more performance input than what is suggested by generativists. Parents must provide the communication aids that children need in order to acquire language. According to Vygotsky (1962) language is only initially something used for young children to interact socially and is only developed over time to become something else. Interactionists also believe that maturation and cognition are an essential part of language acquisition and that until a child is at a certain level of cognition; they will be unable to acquire language.
Similar to behaviourists, the environment is where interactionists believe language skills appear, but more emphasis is placed on social development than on Piaget's cognitive development. Non-linguistic elements (turn-taking, mutual gaze and joint attention) are necessary for social development along with motherese, or child-directed speech (CDS) which is a specific way of speaking to children that differs to how adults communicate with one another. Bruner, as cited in Harley (2008) claims language development occurs within a language acquisition socialization system (LASS) which contains these innate non-linguistic elements.
In positively evaluating this theory, those in favour, believe that CDS is an assisting factor in child language acquisition. This is confirmed by studies of fourteen different languages and proves that infants have preference over this kind of speech. In a study by De Casper and Fifer from 1980, infants are found to prefer their own Mother's CDS over another Mother's CDS. Berko Gleason (2005). In a study cited in Berko Gleason (2005), by Tomasello and Farrar from (1986), it appears that Mothers who focus on the object of their child's gaze have children who speak their first words earlier and also have larger vocabularies. Despite positive evidence from studies, detailed analysis on how development is influenced by social interactions is insufficient.
As already mentioned, evidence suggests further testing is needed in the area of social interactionism. An explanation for the lack of detail is provided by Berko Gleason (2005) and suggests two of the issues with this theory are that it does not exist in all languages, and it has not been in existence for the same length of time as other theories, so may not have the counter evidence to compare it to. To date, studies have shown the difference of features between CDS and adult-like speech, yet the existence of these patterns does not prove the assistance in the acquisition of language for children. A suggestion is made by Baker and Nelson, cited in Berko Gleason (2005) that it is difficult to know whether language development is caused by parents' lack of communication or childrens'. Research of language delays in neglected children suggest that the childrens' impairments may de-motivate parents with the result being neglectful parenting.
An example where social interactionism can assist in the area of speech and language therapy is the previously mentioned example of Genie. Genie's experience of neglect highlights the evidence that the correct environment is necessary for language learning, that a specific social context is required for normal language learning to occur. This knowledge can assist in the assessment and evaluation of a neglected child. Another example, such as the Hanen programme, is based on the social interactionist model where parents facilitate language learning in everyday situations, but as it requires a lot of parental input at home, it may be a difficult kind of intervention to apply in practice.
To conclude the social interactionist analysis, this approach takes from both the linguistic theory in terms of children having an innate specialized language device and from the behaviourist theory; it values the influence of the environment on language acquisition.
This essay looked at three theories of language acquisition: the linguistic theory, behaviourist theory and social interactionist theory. Each theory included an explanation of the theory, discussed whether it took a nativist or empirical approach and whether the evidence was more focused on competence or performance. The evidence supporting and criticising the theories was included along with examples of how the theories applied to the areas of speech and language therapy.