| Three studies are presented investigating the role of developmental instability (DI) in human cognitive and personality functioning. Two measures of DI were used, fluctuating asymmetries (FA) and minor physical anomalies (MPAs). Study One examined several measures of psychometric intelligence with respect to measures of DI. A DI composite score (not FA or MPAs individually) was negatively correlated with psychometric intelligence. Study Two involved the combination of MRI structural and MEG functional neuroimaging to assess a number of brain asymmetries, as well as neural speed and reaction time as predictors of psychometric intelligence, in the context of DI. A composite body FA score correlated significantly with a brain asymmetry deviation (BAD) score (a composite of cortical deviation, white matter deviation and planum temporale deviation). DI correlated negatively with cerebral hemisphere and cortical size, controlling for overall brain size. Cerebral hemisphere and cortical volume correlated positively with psychometric intelligence. It was also found that DI predicts variability in reaction time, which is significantly correlated with intelligence test scores. Psychometric intelligence was found to correlate with MEG measures of brain speed, but only for conditions in which a decision was required, and only for specific MEG determined aspects of task processing (primarily those related to decision time). It was concluded that normal variability during development has profound consequences for individual differences in both the structure and function of the brain in normal individuals, and that this brain variability is related to individual variation in psychometric intelligence. Finally, DI was found to be positively correlated with scores on the Golden and Meehl Schizoidia Scale and The Magical Ideation Scale, but not The Social Anhedonia Scale in a population of university students. This finding is discussed in the context of evolutionary psychology and the role of psychosis proneness as a marker of DI. |
