COVERT ORIENTING TO NON-INFORMATIVE CUES - REACTION-TIME STUDIES

Lateralized, non-informative visual cues lengthen reaction time (RT) t o successive targets flashed in the same hemified. Early ipsilateral R T facilitation is limited to the co-occurrence of cues and targets. In hibition from visual cues has sensory components which do not depend o n orienting, as well as attentional components which are limited to on e side of the vertical meridian. An inhibition of RT to targets ipsila teral to the cues has been found with somatic or auditory cues and tar gets, and also when somatic targets follow visual cues or visual targe ts follow somatic cues. The results reviewed in this paper (1) are bes t accounted for by directional constraints in motor readiness which ar e induced by the voluntary suppression of an overt orienting toward th e location of the cue; (2) indicate that similar mechanisms of covert orienting operate in the whole peripersonal and near extrapersonal spa ce; and (3) point to a common neural substrate mediating both intramod al and cross-modal effects.