Linguistic perforl 11 ance in children who develop schizophrenia in adult life Evidence for normal syntactic ability

Syntactic complexity refers specifically to the level of embedding of dependent clauses (or subordination) and coordination of clauses within a sentence (see Appendix for examples). In adults these act as good measures of the ability to generate syntax, whereas in children/adolescents these are indices of syntactic maturity. Depth of embedding can vary from no embedding at all to deeper levels. A sentence with clausal embedding at level two, or deeper levels, is referred to by Morice & Ingram (1983), and ourselves, as a 'complex sentence'. Coordination refers to joining clauses in a linear fashion, or stringing them end-to-end (see Appendix). Adults with schizophrenia fail to use embedding to the same extent as adults without psychiatric problems. Both Morice & Ingram (1983) and Thomas et al (1990, 1996) conclude that this impoverished use of syntax reflects a premorbid deficit in syntactic production, probably indexing abnormal neurodevelopment. However, syntactic ability has not been assessed directly in children before they develop schizophrenia. The studies of Morice & Ingram (1983) and Thomas et al (1990, 1996) were restricted to clausal embedding within sentences, and have ignored syntactic complexity at the level of the phrase. Phrases can be pre-modified or postmodified (see Appendix). Development tends to follow the path of increasing complexity, that is level one pre-modification precedes level two and above. Post-modification comes later still than pre-modification, and would be achieved by the age of 11 in all but a very small number of disabled children (Crystal et ai, 1989). Thus, analysis of phrase structure allows for an additional way of investigating the level of syntactic complexity. If the syntactic ability of children who subsequently developed schizophrenia in adult life is of a less complex nature than that of the normal population, then we would expect to find that these children would demonstrate similar usage of zerollevel one pre-modification but less usage of level two and higher, and produce less postmodification than controls. Such a finding would simply reflect how these children use syntax, but could not offer any valuable insights into neurodevelopmental theories of schizophrenia. For children who later developed affective psychosis or neurotic disorder our ad hoc hypothesis is that their developmental level, or use of syntax, would be similar to the normal controls on all measures. 'Syntactic deviance', or inability to apply the rules of syntax correctly, is somewhat different to reduced complexity of embedding. Syntactic deviance has been found to occur more frequently in adults with schizophrenia by some (Chaika & Alexander, 1986; Hoffman & Sledge, 1988), but not all (Lecours & VanierClement, 1976; Cohen 1978; Fraser et aI, 1986). Furthermore Fromkin (1975) reported that the types of error reported were similar to slips of the tongue often found in most psychiatrically well adults. Hoffman & Sledge (1988) found that at least 100/0 of clauses were syntactically deviant (using a conservative measure), compared with 4.50/0 in controls, but this deviance was episodic. Chaika & Alexander (1986) found that agrammatisms did occur in the form of syntactic gaps (that is, failure to provide the head of constructions and 'word-salads') and that such instances "were not at all difficult to find". However, these aggrammatisms may well be confined to the most severel chronic cases of schizophrenia.