Evidence for subgroups of adextrals based on speech lateralization and cognitive patterns

Abstract

Some non-right-handers may prefer the left hand by virtue of well-organized or high levels of spatial ability, vested primarily in the right hemisphere, rather than as a result of anomalous speech representation. This study tested the hypothesis that adextral (left-handed or ambidextrous) individuals with high spatial ability might have cerebral speech lateralization patterns similar to dextrals. Paper-and-pencil tests of various cognitive abilities, a verbal dichotic listening task, and a handedness inventory were administered to two groups (science or non-science students) of adextral and dextral subjects. The science group had predictably higher spatial ability than the non-science group. Adextral science students were as lateralized on dichotic listening, and had equal spatial ability, compared to dextral science students. Adextral non-science males were less lateralized and had (unexpectedly) poorer spatial ability than dextral non-science males. Thus in adextrals, variations in ability patterns may be related to variations in speech lateralization.