A temporal benefit of covert spatial orienting across visual hemifields.
26.551, Saturday, 17-May, 2:45 pm - 6:45 pm, Pavilion
Chris Angeloni1, Jocelyn Sy1, Frank Tong1; 1Department of Psychology, Vanderbilt University
Recent work has demonstrated significant performance advantages in tasks spanning both visual hemifields, implicating the presence of two partially independent resources in each hemisphere that can process visual input in parallel. This effect has been demonstrated in a variety of visual domains, selectively enhancing attentional tracking (Alvarez & Cavanagh, 2005) and visual short-term memory for spatial locations (Delvenne, 2005) and also exhibiting reduced susceptibility to the attentional blink (Scalf et al., 2007). The current study examined the temporal dynamics of covert attentional orienting within and across hemifields to determine whether a similar advantage would be observed for serial shifts of attention. Participants performed a rapid serial visual presentation (RSVP) task on one of four simultaneously presented RSVP streams, each stream presented in each visual quadrant. We manipulated the direction of attentional orienting by cuing participants to first attend to one RSVP stream. Subsequently, within that stream, a cognitive cue indicated that the participant should switch their attention to a different RSVP stream that was either in the current hemifield or the opposite hemifield. Participants were instructed to report the first character that they perceived following the attentional shift to the second RSVP stream. The temporal lag between the cognitive cue and the reported letter was assumed to reflect the time needed to process the cognitive cue and to spatially reorient attention. We found a significant interaction effect between lag and the direction of attentional reorienting. Post-hoc comparisons revealed a temporal benefit in reporting letters 300ms after the cue when attention was shifted across hemifields, in comparison to when shifting within the same visual hemifield. These findings suggest that participants spatially reoriented attention more quickly across hemifields than within hemifields, supporting the notion that partially independent attentional resources in the two hemispheres can support faster shifts of attention across hemifields.