The influence of attention on the dichotic REA.

Laterality researchers have frequently neglected to control for possible attentional components of perceptual asymmetries. Attention was manipulated in a dichotic listening paradigm by presenting a pre-exposural tone cue to the ear from which the subject was required to report. The time period between the onset of the cue and the onset of the trial (Stimulus Onset Asynchrony--SOA) was varied such that the time available to orient attention was manipulated. In two experiments, sizeable REAs were apparent at the shortest SOA (150 msec) but were substantially attenuated at longer intervals (450 and 750 msec SOA). In addition, a much larger effect of SOA on left-ear than on right-ear performance was observed. These effects were taken as evidence of an attentional bias to the right ear in the typical dichotic listening situation.