Selective and divided attention: Spatial orienting in a semantic classification task

Preliminary data from our lab using non-lexical stimuli (alphabet letters) suggests that auditory spatial attention may act as a filter with some spatial roll-off (seen in patterns of false alarms to targets in unattended spatial streams). The current project extends that research, examining the interaction between auditory spatial attention and lexical activation. In a semantic classification task, listeners respond to words of a target class only when they occur in designated spatial streams. Streams are temporally interleaved (in random spatial order) to minimize energetic masking. Given that tone-complex experiments suggest a short time course for exogenous spatial reorientations (at least 150 ms but less than 450 ms) [Roberts et al., J. Exp. Psychol. Human 35, 1178–1191 (2009)] when compared to lexical activation (~400 ms) [Pylkkänen et al., Brain Lang 81, 666–678 (2002)], we predict that the additional processing required for semantic classification could paradoxically reduce false alarms in spatial locations proximal to the target stream(s), by delaying the response decision beyond the temporal scope of the exogenous orienting response. We discuss findings in relation to models of exogenous/endogenous attention and lexical processing.