Do People “Pop Out”?

Abstract

The human body is a highly familiar and socially very important object. Does this mean that the human body has a special status with respect to visual attention? In the current paper we tested whether people in natural scenes attract attention and “pop out” or, alternatively, are at least searched for more efficiently than targets of another category (machines). Observers in our study searched a visual array for dynamic or static scenes containing humans amidst scenes containing machines and vice versa. The arrays consisted of 2, 4, 6 or 8 scenes arranged in a circular array, with targets being present or absent. Search times increased with set size for dynamic and static human and machine targets, arguing against pop out. However, search for human targets was more efficient than for machine targets as indicated by shallower search slopes for human targets. Eye tracking further revealed that observers made more first fixations to human than to machine targets and that their on-target fixation durations were shorter for human compared to machine targets. In summary, our results suggest that searching for people in natural scenes is more efficient than searching for other categories even though people do not pop out.

Humans are Detected More Efficiently than Machines in the Context of Natural Scenes

“…The present results support the conclusion of our previous study (Mayer et al, ) in that observers searched for human targets more quickly and more efficiently than they did for machine targets. As we used the same distractors for both target categories in the current work, these results help to rule out the possibility that machine distractors could be recognized and discarded more quickly than human distractors during visual search.…”

“…The search pattern found for human targets in this study and in our previous study (Mayer et al, ) indicates a detection advantage within the human perceptual system for biological but not for mechanical objects. Elsewhere (Cavanagh, Labianca, & Thornton, ; Chandrasekaran, Turner, Bülthoff, & Thornton, ; Thornton, ; Thornton, Rensink, & Shiffrar, ) we have suggested that such an advantage could arise due to the availability of both bottom‐up (Bosbach, Prinz, & Kerzel, ; Mather, Radford, & West, ; Thornton & Vuong, ; Troje & Westhoff, ) and top‐down mechanisms (Bertenthal & Pinto, ; Bulthoff, Bulthoff, & Sinha, ; Thornton et al, ) specifically tuned for processing human form and motion.…”

“…Several lines of previous evidence have suggested that human form and motion could attract attention in this way (New, Cosmides, & Tooby, ; Pratt, Radulescu, Guo, & Abrams, ; Shi, Weng, He, & Jiang, ; Thornton & Vuong, ; Troje & Westhoff, ). However, we found no evidence for pop‐out, either in search times or eye‐movement parameters (Mayer et al, ).…”

“…All aspects of the design and procedure were identical to our previous study (Mayer et al, ) except for the distractor scenes. In separate blocks, participants searched for a scene from the target category (i.e., human or machine) amidst distractor scenes (i.e., always natural motions).…”

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In the context of natural scenes, we recently showed that detecting humans among machine distractors is more efficient than detecting machines among human distractors (Mayer, Vuong, & Thornton, 2015). We concluded that the attentional system is tuned to efficiently process human form and motion.

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