Competition in saccade target selection reveals attentional guidance by simultaneously active working memory representations

Abstract

The content of visual working memory (VWM) guides attention, but whether this interaction is limited to a single VWM representation or functional for multiple VWM representations is under debate. To test this issue, we developed a gaze-contingent search paradigm to directly manipulate selection history and examine the competition between multiple cue-matching saccade target objects. Participants first saw a dual-color cue followed by two pairs of colored objects presented sequentially. For each pair, participants selectively fixated an object that matched one of the cued colors. Critically, for the second pair, the cued color from the first pair was presented either with a new distractor color or with the second cued color. In the latter case, if two cued colors in VWM interact with selection simultaneously, we expected the second cued color object to generate substantial competition for selection, even though the first cued color was used to guide attention in the immediately previous pair. Indeed, in the second pair, selection probability of the first cued color was substantially reduced in the presence of the second cued color. This competition between cue-matching objects provides strong evidence that both VWM representations interacted simultaneously with selection. (PsycINFO Database Record

Figure 1

Example sequence of trial events for Experiment 1A and 1B. Each trial began with a cue stimulus (100ms) presented as a mini checkerboard (1.34×1.34 dva), with two squares (0.63×0.63 dva) for each of the two colors. After a 900-ms delay, two disks (0.67 dva) appeared simultaneously (first pair): one cue-matching and one distractor. Once participants fixated the cue-matching object, the distractor disappeared, and after a 200-ms delay, two new objects appeared simultaneously (second pair). The second pair could contain a same-color cue-matching object with a new distractor (“same”), a new cue-matching object with a new distractor (“switch”), or two objects that each matched a different cue color (“both”). These three conditions were equally probable. Once participants fixated the target in the second pair, the other second-pair object and first-pair target disappeared. Each object had a central vertical or horizontal line (0.04×0.17 dva; light grey, like the background), selected randomly, and participants indicated whether the lines in the cue-matching objects had the same or different orientations. When both objects in the second pair were cue-matching, the line orientation in both objects was the same. In Experiment 1A, the color of the cue-matching object in the first pair changed to grey during the saccade to it, so that there was no direct perceptual match with an object in the second pair. Experiment 1B was the same except that the objects retained their colors until they offset.

Figure 2

Probability of selecting the different types of objects (Cued1: same cue-matching color used in the first pair; Cued2: cue-matching color not used in the first pair; Dist2: novel distractor color) presented in the second pair split by trial type (Switch, Same, or Both). A) Selection probability results from Experiment 1A. B) Selection probability results from Experiment 1B. Error bars indicate within-subjects 95% confidence intervals (Morey, 2008).