| In the dichotic listening paradigm, two different auditory stimuli are presented to the ears simultaneously. Early experiments using dichotic listening revealed that, when the stimuli had linguistic content (e.g., syllables, words, sentences), reports of stimuli presented to the right ear were slightly more accurate than reports of stimuli presented to the left ear. This interesting interaural asymmetry has come to be called the "right-ear-advantage" (REA) and has been the subject of considerable research over the past four decades. Two principal theories have been advanced to explain the phenomenon - the structural model, stressing the importance of the contralateral auditory pathways, and the attentional bias model, stressing the importance of top-down attentional factors.;In this experiment we presented two different words to the two ears, but serially rather than simultaneously. The task for the listener was a semantic category judgment. Does the second word of the pair belong to the same semantic category as the first word of the pair? In half of the paired presentations the first word is presented from the right side, in the other half, from the left side. In both cases the listener must switch attention from one side of auditory space to the other. In a control condition, both words of the pair were presented serially from the same side of auditory space. In half of these pairs both words were presented from the right side. In the other half, both words were presented from the left side.;The experimental measure was the auditory event-related potential (AERP) evoked by the second word of the pair. Using this measure, a significant REA was observed for word pairs that required the switching of attention from the left side to the right side as compared to pairs where the first word was on the right and the second on the left. No REA was observed in the control condition, therefore the observed difference in the switched condition is seen as a result of an asymmetric switching effect, lending further support to the attentional bias model. Such a result confirms that one can achieve a REA without simultaneous presentation. |
