For better or for worse: left-handedness, pathology, and talent.

Geschwind and his colleagues have hypothesized that left-handedness may be a marker for anomalous dominance and is associated with certain immune disorders, learning disorders, and special talents. The few relevant studies done to date have yielded somewhat mixed findings, and little had been done to study the relationship of relevant findings to the definition of handedness employed in a given study. The present study assessed the association between handedness and a variety of disorders, talents, and skills in subjects and their parents and siblings. Results showed that mathematical, artistic, and musical talents varied systematically as a function of handedness. Verbal skills, stuttering, and asthma were also significant discriminators in some discriminant function analyses, and certain variations in the definition of handedness produced systematic variations in results. Finally, certain disorders, particularly eczema, stuttering, and epilepsy, in the parents were related to handedness in their offspring.