Abstract
There is evidence that the presence of predictive cues typically improves performance in visual search tasks (e.g. Eckstein et al., 2000; Palmer et al., 2000). Here, we present a novel finding in which search performance was hindered by predictive cues at high signal contrasts. Method: Participants performed a visual search task in which they were to identify one of five letters (A–E) at one of five signal contrasts embedded in white noise. In cued trials, four colored circles were overlaid on the image with their colors indicative of how likely they were to contain the target (Red:40%, Green:20%, Blue:10%, Yellow:10%). The arrangement of the cued regions was arbitrary and identical across trials and participants. In the remaining 20% of trials, the target appeared outside of the cue circles. For uncued trials, stimuli were constructed identically (including the probabilistic structure of the target location) except for the absence of the circles. Results: Performance at low signal contrasts was higher for cued trials than uncued trials, mirroring traditional cueing effects. However, at high signal contrasts, observers achieved higher performance on uncued trials than cued trials. We suggest that these results arose from the overweighting of information at cued locations which impeded performance when targets were easily detectable. Behavioral results support this hypothesis, as performance for the 20% trials in which targets appeared outside the four probabilistically-defined cue areas was significantly lower for cued trials (circles present) than uncued trials (circles absent). Additionally, the frequency of eye movements towards high contrast targets appearing outside of the four probabilistically-defined cue areas sharply diminished when the cue circles were present. Conclusions: While observers often exploit predictive cues to enhance visual search performance, suboptimal overutilization of that statistical information in the guidance of saccadic eye movements can hinder performance when targets are easily detectable.