Studies on Endogenous and Exogenous Visual Selective Attention

Abstract

Studies of mechanisms underling 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. Direct peripheral cues and symbolic central cues are believed to activate different exogenous and endogenous modes of orienting. To further investigate the possibility of auditory symbolic cues to activate endogenous visual selective attention, three experiments are presented in this paper. Experiment 1 compared visual and auditory symbolic cues. Results showed that valid auditory cues come with inhibition rather than facilitation at Stimulus Onset Asynchronies (SOA) shorter than 500ms, while valid visual cues showed significant facilitation even at the shortest SOA (100ms). At longer SOA, both cue show facilitation. It was suggested that there exists a super-modal mechanism, but the visual and sound cues have important difference in activating visual selective activities. Experiment 2 tested the effect of a peripheral cue on the discrimination of targets with different eccentricities. Results showed that the peripheral onset captured attention involuntarily and the spatial-temporal character was more consistent with the hypothesis of a spotlight model of attention shift than that of a zoom-lens model or a spatial gradient model. The attention spotlight needed 25 ms to move 1 visual degree. Experiment 3 presented the peripheral onset following either visual or sound symbolic cues, and showed that a peripheral onset could not capture attention when attention was focused on locations incompatible with the onset location. When the peripheral onset was consistent with the cue, facilitation in reaction time was found. The difference between visual and sound cues was also found. The study findings might contribute in improving computer displays designed to special and complex environment.