Abstract: Studies of mechanisms underlying orienting of attention in visual space usually provide subjects with advance cues. These cues indicate the probable locations of targets to facilitate localizing and discriminating the targets. Symbolic central cues and direct peripheral cues are believed to activate different endogenous and exogenous modes of orienting. Endogenous attention involves voluntary orienting response to symbolic indicators,such as a central arrow (central cue);and exogenous attention involves reflexive orienting in response to salient stimuli in the visual field,such as a peripheral flash (peripheral cue). Endogenous selective attention can be inferred from performance differences in detecting signals at expected and unexpected spatial locations. For example,a central cue pointing to the likely target location can direct attention to that location. Compared to a neutral and an invalid cue,spatially valid cues result in benefits,measured in shorter latencies and less errors. Alternatively,attention can be controlled by external factors. In everyday life,attentional selection is often accompanied by cross modal coordination. Many everyday situations require attention available to several sense modalities. Some studies have reported positive effects of spatial cueing on auditory judgements. Spence and Driver(1994) were able to demonstrate unambiguous covert auditory orienting effects. Researches on endogenous and exogenous mechanisms of selective attention operating both auditory and visual cues provoke the question of how they may be linked across modalities. To further investigate the possibility of auditory symbolic cues to activate endogenous visual selective attention,one experiment controlled by an AST DX66 PC was designed to examine the effect of auditory central cues on cross modal selective attention. The peripheral abrupt onsets were presented following the auditory symbolic cues and a target identification paradigm was used. The results showed that valid auditory cues had a significant facilitation at SOA longer than 200ms and a peripheral abrupt onset could capture attention when attention was focused on one of the space locations. The auditory cue validity was apparent on between modality trials. In addition,these effects were interpreted as evidence of separate auditory and visual spatial selective attention mechanisms,but with links such that auditory orienting tends to result in visual orienting to corresponding location in visual space.

Key words: endogenous, exogenous, cross modality