Humans are detected more efficiently than machines in the context of natural scenes

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. However, our results are also consistent with the possibility that discarding machine distractors is more efficient than discarding human distractors. In the present study, we replicated our previous visual search experiment but this time embedded targets amongst the same type of distractors; namely scenes displaying natural motion (e.g., billowing clouds, trees moving in the wind). Detecting humans among natural motion was more efficient than detecting machines among the same distractors as reflected in shallower search slopes, smaller intercepts, shorter first fixation durations on targets, and higher percentages of first fixations on targets. These findings are in line with efficient detection of human targets but not with efficient discarding of machine distractors