Sex differences and asymmetry of lexical processing: effects of responding hand, stimulus familiarity and intraexperimental experience

Word frequency and the lateralization of lexical processes

Despite the extensive clinical and neuropsychological evidence for major differences in language function between the left and right hemispheres, it has proven difficult to demonstrate reliable differences in lexical processing. It is particularly surprising that frequency has been found to have no differential effects upon word recognition in the hemispheres, in view of the evidence that this variable has significant effects upon lexical processing. It is possible, however, that any interaction between word frequency and hemispheric processes is too subtle or too complex to be revealed by the simple dichotomous studies previously attempted. This study manipulated word frequency across seven levels in an effort to provide a fine-grained insight into the relationship between word frequency and lexical processing in the hemispheres. The results revealed a clear additivity between visual field and word frequency across all levels of frequency, for both RT and errors. Such findings create difficulties for the interpretation of studies of lateralized lexical access in general, and are particularly hard to reconcile with lateral asymmetries revealed in other aspects of lexical processing. It is proposed that a resolution of this problem may depend upon the development of theories that emphasise the notion of laterally distributed word representations, rather than discrete lexical structures on each side of the brain.

Sex differences and cognitive/motor interference with visual half-field stimulation

This study examines the possible influence of the response on the asymmetry of lexical decision in a visual half-field study and whether sex differences in asymmetry might be determined by response factors. The results support the importance of these factors: when response demands were increased (pressing the button three times instead of once) the reaction time asymmetry was reversed for male subjects.