A salient and task-irrelevant collinear structure hurts visual search

Abstract

Salient distractors draw our attention spontaneously, even when we intentionally want to ignore them. When this occurs, the real targets close to or overlapping with the distractors benefit from attention capture and thus are detected and discriminated more quickly. However, a puzzling opposite effect was observed in a search display with a column of vertical collinear bars presented as a task-irrelevant distractor [6]. In this case, it was harder to discriminate the targets overlapping with the salient distractor. Here we examined whether this effect originated from factors known to modulate attentional capture: (a) low probability-the probability occurrence of target location at the collinear column was much less (14%) than the rest of the display (86%), and observers might strategically direct their attention away from the collinear distractor; (b) attentional control setting-the distractor and target task interfered with each other because they shared the same continuity set in attentional task; and/or (c) lack of time to establish the optional strategy. We tested these hypotheses by (a) increasing to 60% the trials in which targets overlapped with the same collinear distractor columns, (b) replacing the target task to be connectivity-irrelevant (i.e., luminance discrimination), and (c) having our observers practice the same search task for 10 days. Our results speak against all these hypotheses and lead us to conclude that a collinear distractor impairs search at a level that is unaffected by probabilistic information, attentional setting, and learning.

Fig 1. Examples of the search display in Jingling and Tseng (2013).

The target is either overlapping (A or C) or non-overlapping (B or D) with the distractor. The distractor can be of long (21 bars) (A, C or D) or short collinear (3 bars) (B) in the distractor column. The configuration can be collinear vertical (A, B) or non-collinear (C), or collinear horizontal (D). The target is highlighted in (A) but not shown in experiment.

Fig 2. Illustration of main findings in Jingling and Tseng (2013).

(A) The effect of distractor configuration. (B) The effect of distractor size.

Fig 3. Results of chance occurrence in Experiment 1 (A), and high occurrence in Experiment 2 (B).

Red columns are data for non-overlapping targets, while blue columns are data for overlapping targets. The asterisk indicates significant differences (p < .05) between conditions.

Fig 4. Part of the search display used in this experiment.

The target is a brighter bar and overlaps with the salient collinear column in this example.

Fig 5. Results of Experiment 3.

The error bars are the standard error of the mean.

Fig 6. Overall responses across 10 sections.

The upper panel is data of response times, while the lower panel is accuracy. The error bars are the standard error of the mean.

Fig 7. RTs of each condition for the four participants.

The error bars are the standard error of the mean.

Fig 8. Search impairment index on RT in each session.

The error bar is the standard error of the mean.