Learning what goes with what

Abstract

Hard as it is to learn which words go together in a sentence, children must also learn which words (and morphemes) go together without actually being together in a sentence. For example, the English progressive tense consists of two parts, the verb ‘be’ and the verbal ending ‘-ing’. These parts must be separated by at least the verb stem to which ‘-ing’ attaches (e.g. ‘be baking’) but may be separated by an indefinitely long string of words and syllables (e.g. ‘be not very happily baking’). Despite this discontinuity, the child must learn that the two parts are dependent on each other. Santelmann and Jusczyk recently addressed the question of when, and to what extent, infants are able to appreciate these relationships 1 Santelmann L.M. Jusczyk P.W. Sensitivity to discontinuous dependencies in language learners: evidence for limitations in processing space. Cognition. 1998; 69: 105-134 Crossref PubMed Scopus (169) Google Scholar . They used a method known as the ‘headturn preference procedure’ to test whether infants could discriminate between auditory passages containing normal progressives (‘is’ plus ‘-ing’, e.g. ’Mary is baking’) and passages in which the auxiliary was changed to the ungrammatical ‘can’ (‘can’ plus ‘-ing’, e.g. ‘Mary can baking’). Assessment of headturn behaviour, as an index of attention to the sentence being heard, revealed that 18-month-olds noticed the substitution of ‘can’ for ‘is’ but 15-month-olds did not. Even the 18-month-olds’ ability appeared to depend on how discontinuous the dependency was. They could still detect the switch if there was a two-syllable intervening adverbial phrase (e.g. ‘is quickly baking’) but failed to notice the dfference if the intervening material was more substantial (e.g. ‘is very quickly baking’). These results provide concrete evidence about the size of children’s early processing window, a crucial constraint on any learning algorithm. Moreover, a post-hoc analysis showing that performance was partially dependent on whether infants had yet reached the two-word stage in speech production argues that the development of syntactic competence is an important factor in identifying complex grammatical dependencies.