Distributed attention beats the down-side of statistical context learning in visual search

Abstract

Spatial attention can be deployed with a narrower focus to process individual items or distributed relatively broadly to process larger parts of a scene. This study investigated how focused- versus distributed-attention modes contribute to the adaptation of context-based memories that guide visual search. In two experiments, participants were either required to fixate the screen center and use peripheral vision for search ("distributed attention"), or they could freely move their eyes, enabling serial scanning of the search array ("focused attention"). Both experiments consisted of an initial learning phase and a subsequent test phase. During learning, participants searched for targets presented either among repeated (invariant) or nonrepeated (randomly generated) spatial layouts of distractor items. Prior research showed that repeated encounters of invariant display arrangements lead to long-term context memory about these arrays, which can then come to guide search (contextual-cueing effect). The crucial manipulation in the test phase was a change of the target location within an otherwise constant distractor layout, which has previously been shown to abolish the cueing effect. The current results replicated these findings, although importantly only when attention was focused. By contrast, with distributed attention, the cueing effect recovered rapidly and attained a level comparable to the initial effect (before the target location change). This indicates that contextual cueing can adapt more easily when attention is distributed, likely because a broad attentional set facilitates the flexible updating of global (distractor-distractor), as compared to more local (distractor-target), context representations-allowing local changes to be incorporated more readily.

Figure 1.

Example search display presenting a repeated target-distractor configuration. In the display, the target position swaps with a distractor from the opposite hemifield across the learning and test phases, while all other items remain unchanged—so as to examine how the target location change affects the RT advantage for repeated versus nonrepeated displays (the contextual-cueing effect) when visual search is performed under distributed—versus focused-attention conditions. Note that the red, dashed circles, depicting the three concentric rings on which the search items were arranged, were not shown in the actual search displays. In the distributed attention condition, no fixation cross was shown in the actual search displays.

Figure 2.

Distributed and focused attention conditions (left and right panels, respectively). The upper panels of the figure depict mean RTs (in ms) and associated standard errors for repeated and non-repeated displays as a function of epoch in the learning and test phase. The panels in the lower half represent the corresponding mean contextual-cueing effects (in ms) in each epoch.

Figure 3.

Mean contextual-cueing effects (in ms) in the distributed attention and focused attention conditions (left and right panels, respectively) in each epoch, plotted for the sub-group of 37 participants who showed cueing effects in the learning phase.

Figure 4.

Analyses of eye movements in the focused attention condition: contextual-cueing effects (i.e., gaze measure in non-repeated minus repeated displays) are shown for mean saccade amplitudes and mean number of fixations (left and right panels, respectively) as a function of epoch in the learning and test phases and separately for the entire sample of 26 participants (top panels) or for a subset of 18 observers who showed contextual cueing initially during learning (bottom panels). Error bars: mean standard errors.