Importance of attentional mechanisms in audiovisual links

The effect of auditory cues at different levels of visual processing was ex amined by using a visual "conjunction of features" discrimination task (exp eriment 1) and a "feature" discrimination task (experiment 2). In both expe riments the visual target, appearing either on the left or the right of Ss' midline, was preceded by a brief tone either spatially proximal or distal to the target. In the "conjunction" task, subjects had to discriminate the orientation of a T flanked with T distracters of different orientations. In this task, assumed to require focused attention, discrimination accuracy w as increased when the sound cue occurred at the subsequent visual target lo cation and was decreased when it occurred at its alternative location. In t he "feature" experiment, subjects had to discriminate the orientation of a line segment (+45 degrees) presented among line segment distracters. Accura cy was not affected, either when the sound was proximal or when it was dist al to the location of the visual target. Results suggest that the early pro cessing of sensory information is modality specific and that interference o f auditory stimulation with visual stimuli is more pronounced as the proces sing of visual stimuli requires focused attention.