VISUAL-AUDITORY INTERACTION IN SPEEDED CLASSIFICATION - ROLE OF STIMULUS DIFFERENCE

An experiment examined cross-modal interference and congruence in spee ded classification: Subjects had to identify compound (visual-auditory ) stimuli as either low or high in spatial position (visual judgment) of low or high in pitch (auditory judgment), in 16 conditions, each of which combined one of four possible pairs of tones, varying in freque ncy difference, with one of four possible pairs of dots, varying in po sitional difference. Both classification by position and classificatio n by pitch revealed Garner interference (poorer performance than basel ine, with orthogonal variation in the irrelevant dimension) and congru ence effects (better performance with congruent than with incongruent stimulus combinations), but pitch classification showed more. Furtherm ore, the size of the pitch difference strongly affected classification by pitch and less strongly affected classification by position, but t he size of the position difference affected neither. The findings are consistent with the view that Garner interference and congruence effec ts are closely related, perhaps arising from a common source, and sugg est that the asymmetries could depend in part on the degree of dimensi onal overlap between stimuli and responses.