Optimal search by initially looking away from the target in the presence of remote cues
33.429, Sunday, May 12, 8:30 am - 12:30 pm, Orchid Ballroom
Stephen C. Mack1, Emre Akbas1, Miguel P. Eckstein1; 1University of California, Santa Barbara
During visual search, humans often direct their eyes towards image regions which resemble the target (Rao et al., 2002; Zelinsky, 2008) or toward objects which often spatially co-occur with search targets (Eckstein et al., 2006; Torralba et al., 2006). This behavior is consistent with a saccadic targeting (maximum a posteriori) model, which often approximates the ideal searcher. Here, we report a scenario in which an ideal searcher and humans initially look away from the target in the presence of remote spatial cues to optimize performance. Method: Observers performed a free eye movement search task in which they were to indicate the presence of a Gabor (12 cycles/º) embedded in white luminance noise. The target appeared at one of ten locations arranged in two semi-circles. The orientation of three remote spatial cues (large CÂ’s), situated between the two groups of target locations (eccentricity 5º), indicated where the target would appear if it were present. Observers performed task variants in which the cues differed in whether they provided target location information (CÂ’s vs. OÂ’s), how visible the information in the cues was (large vs. small gap), or whether the cues could be foveated. Results: Performance when remote cues were predictive (95.1±.3%) vastly exceeded that of when the cues did not predict location (60.9±.2%). Moreover, observers systematically directed early saccades towards the cues when they provided target location information. When cues were non-predictive, they were largely ignored and a sequence of eye movements which surveyed as many target locations as possible prevailed. Critically, when cues were predictive but observers were prevented from foveating them, performance suffered (62.5±.5%) compared to when saccades were unrestricted. Conclusions: Humans display initial eye movement patterns which depart from a well-established saccadic targeting strategy when these atypical saccades can enhance performance, as is the case with remote spatial cues.