Thomas R. Przybeck

The Tridimensional Personality Questionnaire is a self-report personality inventory measuring three major personality dimensions: Novelty Seeking, Harm Avoidance, and Reward Dependence. Normative data, based on a U.S. national probability sample of 1,019 adults, are presented and the psychometric properties of the questionnaire are discussed.

An invariant feature of pervasive developmental disorders (PDDs) is a relative deficit in the capacity for reciprocal social behavior (RSB). The authors acquired teacher reports of RSB in 287 schoolchildren and parent reports of RSB in 158 child psychiatric patients using a new research instrument, the Social Reciprocity Scale. Total scores on this measure of RSB were continuously distributed in all groups of subjects; children with PDDs scored significantly higher for the degree of deficits in RSB than did clinical or nonclinical controls. Latent class analysis and factor analysis failed to demonstrate separate categories of deficiency for core autistic symptomatology and more general impairments in RSB, consistent with the notion of a "broader autism phenotype." Assessments of RSB on a continuous scale may be useful clinically for characterizing the behavior of children whose social deficits fall below the threshold for a full diagnosis of autism. They may also be useful in genetic-linkage studies of autistic spectrum disorders.

BACKGROUND: Although DSM-IV requires symptoms in three criterion domains for a diagnosis of autistic disorder, the extent to which those domains are phenotypically independent is an unanswered and important question. The identification of 'endophenotypes' of the autistic syndrome may be very useful for genetic and neurobiologic studies of autism, but only if they represent truly independent sub domains of the disorder. METHODS: In this study we examined the factor structure of autistic traits using data from 226 child psychiatric patients with and without pervasive developmental disorders, employing cluster analysis of data from the Autism Diagnostic Interview-Revised (ADI-r) and principal components factor analysis of data from the Social Responsiveness Scale (SRS, a quantitative genetic measure of autistic traits formerly known as the Social Reciprocity Scale). RESULTS: The results were consistent with the existence of a singular, continuously distributed underlying factor, resulting in disparate phenotypic manifestations across the three criterion domains for autistic disorder (social deficits, language deficits, and repetitive/stereotypic behaviors). CONCLUSION: The analyses generally failed to support the existence of independent sub domains of dysfunction in autism spectrum conditions. Future studies of the association between genetic/neurobiologic markers and autistic symptomatology may be enhanced by approaches which consider autistic symptoms as quantitative traits, and which are informed by ongoing research on the development and phenomenology of core deficiencies in reciprocal social behavior.