Abstract
Focusing attention on a single item isolates it from competitive interactions with nearby stimuli (Reynolds et al., 1999; Kastner et al., 1998). Dividing attention among multiple competing items, however, should fail to isolate the contributions of a single stimulus, leaving their competitive interactions unchanged. Our previous work (Scalf & Beck, in press) confirms that directing attention to multiple items produces more competition than does does directing attention to just one of the items. In the current experiment, we investigate whether directing attention to multiple items reduces competition among those items relative to conditions in which they are unattended. We presented participants with arrays of five complex stimuli in the upper right quadrant of the visual field and a stream of digits, letters and symbols at fixation. We manipulated whether attention was directed to the peripheral stimuli by asking participants to monitor either the five peripheral locations for a color/shape/texture conjunction or the fixation stream for an “a”. We manipulated the degree of competition among items by employing sequential and simultaneous presentation conditions. Competition could take place only among simultaneously presented stimuli (Kastner et al., 1998). We find robust competition among items (greater activation under sequential presentation than under simultaneous presentation) across attentional conditions. Although directing attention to five items increased the overall activity they evoked in V4, this effect did not interact with presentation condition; that is, there was no evidence that directing attention to five items reduced their competitive interactions relative to when they were unattended. Our data indicate that when simultaneously directed to multiple competing items, attention is an ineffective remedy for competition for representation.