Contrasting gist-based and template-based guidance during real-world visual search

Abstract

Visual search through real-world scenes is guided both by a representation of target features and by knowledge of the sematic properties of the scene (derived from scene gist recognition). In 3 experiments, we compared the relative roles of these 2 sources of guidance. Participants searched for a target object in the presence of a critical distractor object. The color of the critical distractor either matched or mismatched (a) the color of an item maintained in visual working memory for a secondary task (Experiment 1), or (b) the color of the target, cued by a picture before search commenced (Experiments 2 and 3). Capture of gaze by a matching distractor served as an index of template guidance. There were 4 main findings: (a) The distractor match effect was observed from the first saccade on the scene, (b) it was independent of the availability of scene-level gist-based guidance, (c) it was independent of whether the distractor appeared in a plausible location for the target, and (d) it was preserved even when gist-based guidance was available before scene onset. Moreover, gist-based, semantic guidance of gaze to target-plausible regions of the scene was delayed relative to template-based guidance. These results suggest that feature-based template guidance is not limited to plausible scene regions after an initial, scene-level analysis. (PsycINFO Database Record

Figure 1

Trial event sequence for Experiment 1. Each trial began with a cue presentation (700 ms). After a 1000-ms delay, a memory color was presented for 500 ms for a post-search memory test. After another 700-ms delay, a search scene was presented, which always contained the target (marked by green square, not present in experimental image). The memory color could either match or mismatch a critical distractor object in the scene (marked by red square, not present in experimental image). After responding to the orientation of an “F” (Arial font) on their target object, there was a 500-ms delay before subjects completed a two-alternative forced choice color memory test.

Figure 2

Data figures for Experiment 1. From left to right, data are plotted for the no-cue, category-label-cue, and picture-cue conditions. A) Time (ms) to first fixate the target as a function of distractor color match. B) Overall probability of fixating the critical distractor as a function of color match. C) Proportions of fixations landing on the critical distractor object as a function of ordinal fixation index and color match. D) The distance, in visual degrees, of the current fixation to the target and critical distractor object as a function of ordinal fixation index/number. Error bars indicate within-subjects 95% confidence intervals (Morey, 2008).

Figure 3

Data figures for the analysis of semantic guidance for Experiment 1. A) Elapsed time to first fixation on a target-plausible region as a function of cue type. B) Elapsed number of fixations until first fixation on a target-plausible region as a function of cue type. C) Proportion of fixations on target-plausible regions as a function of cue type and ordinal fixation index. Error bars are standard errors of the mean.

Figure 4

Example stimuli from Experiment 2. The top row depicts a match, plausible scene. The target (blender, outlined in green), matches the color of the critical distractor (outlined in red). Additionally, the critical distractor is in a plausible location for the blender. The bottom row depicts a mismatch, implausible scene. The target (cutting-board, outlined in green), mismatches the color of the critical distractor object (outlined in red). The critical distractor is in an implausible location for the cutting-board.

Figure 5

Data figures for Experiment 2. From left to right, data are plotted for the plausible and implausible conditions. A) Time (ms) to first fixate the target as a function of distractor color match. B) Overall probability of fixating the critical distractor as a function of color match. C) Proportions of fixations landing on the critical distractor object as a function of ordinal fixation index and color match. D) The distance, in visual degrees, of the current fixation to the target and critical distractor object as a function of ordinal fixation index/number. Error bars indicate within-subjects 95% confidence intervals (Morey, 2008).

Figure 6

Trial event sequence for Experiment 3. Each trial began with a 250-ms low-pass filtered preview of the upcoming search scene, allowing participants to extract the scene gist. The preview was followed by a 50-ms mask. After a 700-ms ISI, the picture cue of the search target was displayed for 1000 ms followed by a 500-ms ISI. Finally, the search scene appeared. On a match trial, there was a color match between the target object (backpack, outlined in green) and the critical distractor object (chair, outlined in red).

Figure 7

Data figures for Experiment 3. From left to right, data are plotted for the preview and no-preview conditions. A) Time (ms) to first fixate the target as a function of distractor color match. B) Overall probability of fixating the critical distractor as a function of color match. C) Proportions of fixations landing on the critical distractor object as a function of ordinal fixation index and color match. D) The distance, in visual degrees, of the current fixation to the target and critical distractor object. Error bars indicate within-subjects 95% confidence intervals (Morey, 2008).