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<Paper uid="P05-1025">
  <Title>Automatic Measurement of Syntactic Development in Child Language</Title>
  <Section position="3" start_page="0" end_page="197" type="intro">
    <SectionTitle>
2 The Index of Productive Syntax (IPSyn)
</SectionTitle>
    <Paragraph position="0"> The Index of Productive Syntax (Scarborough, 1990) is a measure of development of child language that provides a numerical score for grammatical complexity. IPSyn was designed for investigating individual differences in child language acqui- null sition, and has been used in numerous studies. It addresses weaknesses in the widely popular Mean Length of Utterance measure, or MLU, with respect to the assessment of development of syntax in children. Because it addresses syntactic structures directly, it has gained popularity in the study of grammatical aspects of child language learning in both research and clinical settings.</Paragraph>
    <Paragraph position="1"> After about age 3 (Klee and Fitzgerald, 1985), MLU starts to reach ceiling and fails to properly distinguish between children at different levels of syntactic ability. For these purposes, and because of its higher content validity, IPSyn scores often tells us more than MLU scores. However, the MLU holds the advantage of being far easier to compute. Relatively accurate automated methods for computing the MLU for child language transcripts have been available for several years (MacWhinney, 2000).</Paragraph>
    <Paragraph position="2"> Calculation of IPSyn scores requires a corpus of 100 transcribed child utterances, and the identification of 56 specific language structures in each utterance. These structures are counted and used to compute numeric scores for the corpus in four categories (noun phrases, verb phrases, questions and negations, and sentence structures), according to a fixed score sheet. Each structure in the four categories receives a score of zero (if the structure was not found in the corpus), one (if it was found once in the corpus), or two (if it was found two or more times). The scores in each category are added, and the four category scores are added into a final IPSyn score, ranging from zero to 112.1 Some of the language structures required in the computation of IPSyn scores (such as the presence of auxiliaries or modals) can be recognized with the use of existing child language analysis tools, such as the morphological analyzer MOR (MacWhinney, 2000) and the part-of-speech tagger POST (Parisse and Le Normand, 2000). However, more complex structures in IPSyn require syntactic analysis that goes beyond what POS taggers can provide. Examples of such structures include the presence of an inverted copula or auxiliary in a wh-question, conjoined clauses, bitransitive predicates, and fronted or center-embedded subordinate clauses.</Paragraph>
    <Paragraph position="3"> 1See (Scarborough, 1990) for a complete listing of targeted structures and the IPSyn score sheet used for calculation of scores.</Paragraph>
    <Paragraph position="4"> Sentence (input): We eat the cheese sandwich</Paragraph>
  </Section>
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