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Language acquisition is the term commonly used to describe the process whereby children become speakers of their native language (firstlanguage acquisition) or children or adults become speakers of a second language (second-language acquisition). Early studies of child development such as

that of the German biologist Tiedemann (1787), Charles Darwin (1877) and Hippolyte Taine (1877) included observations about the development of language. The first detailed study of child language was, according to Campbell and Wales (1970), that of the German physiologist Preyer (1882), who kept a diary of the first three years of his son’s development (Campbell and Wales 1970: 243). He also makes notes on many aspects of development in addition to the linguistic, including motor development and musical awareness. The first published book to be devoted to the study of a child’s language alone was C. and W. Stern’s Die Kindersprache (1907) (not available in English), and it is from this work that the notion of stages of language acquisition (see below) derives (Ingram 1989: 8-9). The diarists’ main aim was to describe the child’s language and other development, although some explanatory hypotheses were also drawn. These typically emphasised the child’s ‘genius’ (Taine 1877), an inbuilt language faculty which, according to Taine, enabled the child to adapt to the language which others presented it with, and which would, had no language been available already, have enabled a child to create one (Taine 1877:

collection was the parental diary in which a linguist or psychologist would record their own child’s development. Ingram (1989: 7) identifies a period of diary studies (1876-1926). With the rising popularity of behaviourist

psychology [see also BEHAVIOURIST LINGUISTICS] after the First World War, longitudinal studies of individual children – studies charting the development of one child over a long period – came to be regarded as insufficient to establish what ‘normal behaviour’ amounted to. Different diaries described children at different intervals and concentrated on different features of the children’s behaviour, so that it was impossible to draw clear comparisons between subjects. Instead, large-sample studies were favoured, studies of large numbers of children all of the same age, being observed for the same length of time engaged in the same kind of behaviour. Several such studies, concentrating on several age groups, would provide evidence of what was normal behaviour at each particular age, and the results of the studies were carefully quantified. Environmental factors were carefully controlled, as behaviourism only took as scientifically valid statements about the influence of the environment on the child’s development: hence, all the children in a given study would come from similar socio-economic backgrounds, and each study would use the same numbers of boys and girls. Ingram (1989: 11ff.) pinpoints the period of

large-sample studies to 1926-57, the period beginning with M. Smith’s (1926) study and ending with Templin’s (1957) study. Studies carried out during this period concentrated mainly on vocabulary growth, mean sentence length, and (Nice

1925) was calculated by counting the number of words in each sentence a child produced and averaging them out. The results for these three areas for what was perceived as normal children (Smith 1926; McCarthy 1930; Wellman et al. 1931) were compared with those for twins (Day 1932; Davis 1937), gifted children (Fisher 1934), and lower-class children (Young 1941). The publication of Templin’s study, the lar-

gest of the period, took place in the year which also saw the publication of Noam Chomsky’s Syntactic Structures (1957; see GENERATIVE GRAMMAR), which heralded the end of the reliance on pure empiricism and behaviourist psychology in linguistic studies [see BEHAVIOURIST LINGUISTICS]. Chomsky’s work and that of his followers highlighted the rule-governed nature of language, and a major focus of attention of many linguists working on language acquisition since then has been the acquisition of morphosyntactic rules, an aspect neglected in earlier large-sample studies. With this aim, longitudinal language sampling in the period from 1957 onwards controlled more carefully the selection of subjects, the research design and the criteria for measurement, aspects which still inform studies of language acquisition. In typical studies of this kind (Braine 1963; Miller and Ervin 1964; Bloom 1970; Brown 1973), at least three separate, carefully selected children – ones which are talkative and just beginning to use multiword utterances – are visited and recorded at regular intervals by the researcher(s). Braine (1963) supplemented this methodology with diaries kept by the children’s parents. Since the 1980s naturalistic data have been

complemented by experimental data of different types: elicited production, judgements on syntax, morphology, semantics and phonology, as well as comprehension tests, which are designed in ways appropriate to the child’s age. In act-out tests, for example, either the child moves toys or reacts to the scene presented. The use of computers has made it possible to analyse large corpora and, thus, to test hypotheses based on larger databases than before.