An investigation of immune system disorder as a "marker" for anomalous dominance

Geschwind and Galaburda (1987) proposed that immune disorder (ID) susceptibility, along with left handedness and familial sinistrality (FS), is a "marker" for anomalous dominance. The theory predicts lesser left lateralization for language processes, lessened left hemisphere abilities, and enhanced right hemisphere abilities. We assessed language laterality (dichotic consonant vowel task) and performances on spatial and verbal tasks. Subjects were 128 college students. The factors of handedness, sex, FS, and immune disorder history (negative or positive) were perfectly counterbalanced. Left-handers were significantly less lateralized for language and scored lower than right-handers on the spatial tasks. Females scored lower on mental rotation than males, but performed comparably to males on the spatial relations task. The only effect of ID was by way of interaction with FS on both spatial tasks--subjects who were either negative or positive on both FS and ID status factors scored significantly higher than subjects negative for one but positive for the other factor. A speculative explanatory model for this interaction was proposed. The model incorporates the notion that FS and ID factors are comparably correlated, but in opposite directions, with hormonal factors implicated by other research as relevant for spatial ability differences. Finally, no support for the "anomalous dominance" hypothesis predictions was found.