Allocation of attention in dichotic listening: effects on the detection and localization of targets within lists

In each of two dichotic listening experiments, 48 normal right-handed adults were instructed to attend selectively to the left and right ears and to divide attention equally between ears. Participants listened for specified targets and reported the ear of entry when the target was heard. Stimuli consisted of lists of digit names in Experiment I and lists of words in Experiment 2. Shifts of attention altered ear asymmetry for localizing but not for detecting digit names. For words, attention shifts altered both detection asymmetry and localization asymmetry, but the effect of attention on detection seemed to reflect differential retrieval from short-term memory rather than differential perception. In both experiments, shifting attention toward either ear resulted in a reporting bias such that signals were attributed to the attended ear more often than to the unattended ear. The results confirm our previous findings, for single pairs of stimuli, that volitional shifts of attention alter response selection rather than perception.