Moving foraging into three dimensions: Feature- versus conjunction-based foraging in virtual reality

Visual attention evolved in a three-dimensional (3D) world, yet studies on human attention in three dimensions are sparse. Here we present findings from a human foraging study in immersive 3D virtual reality. We used a foraging task introduced in Kristjánsson et al. to examine how well their findings generalise to more naturalistic settings. The second goal was to examine what effect the motion of targets and distractors has on inter-target times (ITTs), run patterns, and foraging organisation. Observers foraged for 50 targets among 50 distractors in four different conditions. Targets were distinguished from distractors by either a single feature (feature foraging) or a conjunction of features (conjunction foraging). Furthermore, those conditions were performed both with static and moving targets and distractors. Our results replicate previous foraging studies in many aspects, with constant ITTs during a "cruise-phase" within foraging trials and response time peaks at the end of foraging trials. Some key differences emerged, however, such as more frequent switches between target types during conjunction foraging than previously seen and a lack of clear mid-peaks during conjunction foraging, possibly reflecting that differences between feature and conjunction processing are smaller within 3D environments. Observers initiated their foraging in the bottom part of the visual field and motion did not have much of an effect on selection times between different targets (ITTs) or run behaviour patterns except for the end-peaks. Our results cast new light upon visual attention in 3D environments and highlight how 3D virtual reality studies can provide important extensions to two-dimensional studies of visual attention.