Abstract
Previous research has shown that hand position can influence visual processing in a variety of ways, including enhancing change detection, reducing the effect of distraction, and boosting sensitivity to low-spatial frequency information. These studies have largely used abstract laboratory paradigms; in the current study we explored whether enhanced visual analysis in the space near the hands confers an advantage when applied to a real-world visual search task. We asked participants to search for knives in X-ray images of luggage (a TSA luggage screening task). Stimuli were presented on a tablet computer and participants performed the task by pressing response boxes at the edge of the screen, which forced them to grip the display within their hands, or with a button press on a mouse held in their lap. In the first experiment, there was no effect of hand placement on response times (F(1,67) = 1.50, p = .31) or accuracy (F(1,67) =.003, p = .96). In another experiment, participants were asked to use their finger to trace along the image of the bag to ensure that all potential target locations were inspected. In addition to any effect of hand proximity, it was anticipated that this strategy would encourage a more systematic search. Preliminary evidence suggests that this strategy resulted in substantially longer inspection times (F(1,19) = 10.59, p < .01; a slowing of about 1.6 seconds). Interestingly, this additional time spent viewing the image did not improve accuracy (F(1,19) = 3.18, p = .09; a trend for more false alarms in the finger tracing condition). While basic research suggests that hand proximity can influence visual processing, these experiments suggest that benefits may not scale to more complex situations.
Meeting abstract presented at VSS 2016