Lack of free choice reveals the cost of multiple-target search within and across feature dimensions

Abstract

Having to look for multiple targets typically results in switch costs. However, using a gaze-contingent eyetracking paradigm with multiple color-defined targets, we have recently shown that the emergence of switch costs depends on whether observers can choose a target or a target is being imposed upon them. Here, using a similar paradigm, we tested whether these findings generalize to the situation in which targets are specified across different feature dimensions. We instructed participants to simultaneously search for, and then fixate, either of two possible targets presented among distractors. The targets were defined as either two colors, two shapes, or one color and one shape. In one condition, only one of the two targets was available in each display, so that the choice was imposed. In the other condition, both targets would be present in each display, which gave observers free choice over what to search for. Consistent with our earlier findings, switch costs emerged when targets were imposed, whereas no switch costs emerged when target selection was free, irrespective of the dimension in which the targets were defined. The results are consistent with the operation of different modes of control in multiple-target search, with switch costs emerging whenever reactive control is required and being reduced or absent when displays allow for proactive control.

The Role of Proactive and Reactive Cognitive Control for Target Selection in Multiple-Target Search

“…We reasoned that the presence of both targets would enable observers to use proactive control to prepare a search, whereas the presence of only a single item would require reactive control whenever the observer expected the wrong target. In accordance with previous findings (Ort et al, 2017(Ort et al, , 2018, we found clear switch costs in terms of both saccade latency and saccade accuracy when only one target category was present in a search display, while there were no switch costs when both targets were available. This finding is further supported by the results of hierarchical drift diffusion modeling, which revealed lower drift rates on switch compared to repeat trials when one target was available.…”

“…Supplementary Table S1 provides schematic representations of all types of search displays. Past experiments using a similar paradigm have confirmed that behavior and ensuing switch costs are consistently unaffected by this manipulation (Ort et al, 2017(Ort et al, , 2018, as we also confirm here (see Results).…”

Beta and theta oscillations differentially support free versus forced control over multiple-target search

“…In fact, there was also a reliable, though much smaller, switch cost when target selection was free (t29 = 3.36, p = 0.002). These magnitude differences in switch costs are a direct replication of earlier findings (15,16), and are consistent with, though not conclusive for, a difference in the latency and type of control.…”

“…Here we address the question whether multiple-target search indeed involves switch-related changes in target priority state, and if so, how such state changes are controlled. Recent behavioral evidence from our lab indicates that the environmental context, and the type of cognitive control mechanisms it allows for, determine the occurrence of switch costs in multiple-target search (15,16). Using a gazecontingent search task in which observers looked for two different targets, we found that saccade latencies were prolonged when the target changed from one trial to the next, but only so when either one of the targets was available per display.…”

The roles of relevance and expectation for the control of attention in visual search.

“…The N2pc results from Experiment 2 demonstrate for the first time that such benefits are generated at relatively early stages of attentional target selection, within about 200 ms after stimulus onset. If such color-specific facilitation effects persist across successive search episodes, this may also account for the existence of switch costs during multiple-color search, which have played a prominent role in current debates about the possibility of parallel attentional templates (e.g., Beck, Hollingworth, & Luck, 2012;Ort, Fahrenfort, & Olivers, 2018).…”