Visual field asymmetries in selective attention: evidence from a modified search paradigm

The present study investigated visual field differences in selective attention. Five stimuli were briefly presented and subjects were asked to identify a predefined target. The target/distractor physical similarity varied systematically (low, medium or high) in order to encourage attentional resolving. Right/left hemifield differences were examined in Experiment 1, temporal/nasal hemifield differences in Experiment 2, and upper/lower hemifield differences in Experiment 3. Visual field differences were found only in Experiment 1 suggesting a left/right hemispheric asymmetry in selective attention. These asymmetries appear with increasing stimuli similarity, and suggest that each hemisphere gets involved when attentional selection cannot be carried out without the mode of information processing that characterizes that hemisphere. The absence of other hemifield asymmetries is not in favor of neither a subcortical, nor a specific superior occipito-parietal involvement in attentional resolving and selectivity.