Salient stimuli capture attention and action

Abstract

Reaction times in a visual search task increase when an irrelevant but salient stimulus is presented. Recently, the hypothesis that the increase in reaction times was due to attentional capture by the salient distractor has been disputed. We devised a task in which a search display was shown after observers had initiated a reaching movement toward a touch screen. In a display of vertical bars, observers had to touch the oblique target while ignoring a salient color singleton. Because the hand was moving when the display appeared, reach trajectories revealed the current selection for action. We observed that salient but irrelevant stimuli changed the reach trajectory at the same time as the target was selected, about 270 ms after movement onset. The change in direction was corrected after another 160 ms. In a second experiment, we compared manual selection of color and orientation targets and observed that selection occurred earlier for color than for orientation targets. Salient stimuli support faster selection than do less salient stimuli. Under the assumption that attentional selection for action and perception are based on a common mechanism, our results suggest that attention is indeed captured by salient stimuli.

Dissociable Effects of Salience on Attention and Goal-Directed Action

“…1B; see supplemental methods), we found significant deviation that appeared immediately and persisted through 88% of the movement trajectory (Fig 1C; see methods for details on statistical calculation). This finding is consistent with previous reach movement studies suggesting that action is automatically directed towards physically salient objects [13–15]. The initial trajectory angle (ITA) [17] of hand movements was also greater on distractor present trials (18.7°) than absent trials (15.5°), t (15)= 5.99, p < 001 (Fig.…”

“…For example, one possibility is that differences in the timing of response execution between the two tasks contributed to the divergent results. Nevertheless, the present results provide clear evidence of reduced interference from highly salient distractors during goal-directed action, which are at odds with prevailing views of the impact of salience on performance [7–8] and add to a growing number of studies highlighting dissociations in selection for vision and selection for action [13,16–17]. …”

Goal-directed action is automatically biased towards looming motion

“…A number of previous studies have found that goal-directed action is automatically biased towards perceptually salient feature singleton objects (e.g., Kerzel & Schönhammer, 2013; Wood et al, 2011). The present results build on these findings to show that looming motion can also bias reach movement trajectories automatically.…”

“…2C), p < .001, indicating that the hand was consistently pulled in the direction of looming distractors. Furthermore, this result is not because observers were simply delaying target selection by moving their hand towards the center of all items when a distractor was present 2 (e.g., Kerzel & Schönhammer, 2013). If that were the case, reach movements would be unaffected by the specific looming distractor location.…”

“…Guidance of selection for action can be broken down along similar lines; for example, objects matching task-relevant properties tend to compete more strongly for action (e.g., Castiello, 1999). However, action can also be automatically directed towards a perceptually salient object, such as a color singleton, even when that object is not task-relevant (e.g., Kerzel & Schönhammer, 2013; Wood et al, 2011). …”