Cross-Modal Cues Improve the Detection of Synchronized Targets during Human Foraging

In two experiments, we explored whether cross-modal cues can be used to improve foraging for multiple targets in a novel human foraging paradigm. Foraging arrays consisted of a 6 × 6 grid containing outline circles with a small dot on the circumference. Each dot rotated from a random starting location in steps of 30°, either clockwise or counterclockwise, around the circumference. Targets were defined by a synchronized rate of rotation, which varied from trial-to-trial, and there were two distractor sets, one that rotated faster and one that rotated slower than the target rate. In Experiment 1, we compared baseline performance to a condition in which a nonspatial auditory cue was used to indicate the rate of target rotation. While overall foraging speed remained slow in both conditions, suggesting serial scanning of the display, the auditory cue reduced target detection times by a factor of two. In Experiment 2, we replicated the auditory cue advantage, and also showed that a vibrotactile pulse, delivered to the wrist, could be almost as effective. Interestingly, a visual-cue to rotation rate, in which the frame of the display changed polarity in step with target rotation, did not lead to the same foraging advantage. Our results clearly demonstrate that cross-modal cues to synchrony can be used to improve multitarget foraging, provided that synchrony itself is a defining feature of target identity.