Exploring individual differences in deductive reasoning as a function of 'autistic'-like traits
Fugard, Andrew J. B.
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From a logical viewpoint, people must reason to as well as from interpretations in deductive reasoning tasks. There are two main interpretative stances (e.g., Stenning & van Lambalgen, 2004, 2005, 2008): credulous, the act of trying to infer the speaker's intended model; and sceptical, an adversarial strategy. A range of contextual factors in uence interpretation, but there are also differences between individuals across situations. Taking an individual differences approach, this thesis focuses on reasoning in relation to milder variants of the autism spectrum condition (ASC) phenotype in a typically developing (TD) population. Earlier work on discourse processing in ASC using the `suppression' task (van Lambalgen & Smid, 2004; Pijnacker et al., In press) shows that some aspects of reasoning to interpretations are different in the ASC population. Given that autistic traits involve impairment, e.g., in pragmatic language, and peaks of ability, e.g., in perceptual tasks, it was hypothesised that autistic traits would predict features of the inferences people in the TD population draw. Data were collected from university students on a range of reasoning tasks making it possible to investigate the extent to which interpretation is consistent across task within individuals. Tasks chosen were: conditional reasoning using the `suppression' task and Wason's selection task; one and two-premise Aristotelian quantifer reasoning; the Linda problem; and Raven's Advanced Progressive Matrices. Autistic traits were assessed using the Autism Spectrum Quotient (Baron-Cohen et al., 2001), used previously to study autistic traits in TD individuals, and the Broad Autism Phenotype Questionnaire (Hurley et al., 2007). Autistic traits predicted patterns of inference in many of the tasks. The earlier suppression task result in ASC was replicated and extended in our TD population. Different dimensions of autistic trait related differentially to features of the inferences drawn. Some of the inferences drawn were recognisably related to the credulous versus sceptical distinction and correlated cross-task whilst others were seemingly related to more general topdown versus bottom-up processing preferences. These results provide further evidence of the existence of qualitative individual differences in deductive reasoning. They also show the importance of seeking cross-task correlates to move beyond studies of individual tasks and study reasoning to and from interpretations in the same individual.