Failure to exploit learned spatial value information during visual search

ABSTRACT

In recent years there has been rapid proliferation of studies demonstrating how reward learning guides visual search. However, most of these studies have focused on feature-based reward, and there has been scant evidence supporting the learning of space-based reward. We raise the possibility that the visual search apparatus is impenetrable to spatial value contingencies, even when such contingencies are learned and represented online in a separate knowledge domain. In three experiments, we interleaved a visual choice task with a visual search task in which one display quadrant produced greater monetary rewards than the remaining quadrants. We found that participants consistently exploited this spatial value contingency during the choice task but not during the search task – even when these tasks were interleaved within the same trials and when rewards were contingent on response speed. These results suggest that the expression of spatial value information is task specific and that the visual search apparatus could be impenetrable to spatial reward information. Such findings are consistent with an evolutionary framework in which the search apparatus has little to gain from spatial value information in most real world situations.     

Redundancy effects in the perception and memory of visual objects

Is visual representation of an object affected by whether surrounding objects are identical to it, different from it, or absent? To address this question, we tested perceptual priming, visual short-term, and long-term memory for objects presented in isolation or with other objects. Experiment 1 used a priming procedure, where the prime display contained a single face, four identical faces, or four different faces. Subjects identified the gender of a subsequent probe face that either matched or mismatched with one of the prime faces. Priming was stronger when the prime was four identical faces than when it was a single face or four different faces. Experiments 2 and 3 asked subjects to encode four different objects presented on four displays. Holding memory load constant, visual memory was better when each of the four displays contained four duplicates of a single object, than when each display contained a single object. These results suggest that an object's perceptual and memory representations are enhanced when presented with identical objects, revealing redundancy effects in visual processing.     

Flexible target templates improve visual search accuracy for faces depicting emotion

Theories of visual attention hypothesize that target selection depends upon matching visual inputs to a memory representation of the target – i.e., the target or attentional template. Most theories assume that the template contains a veridical copy of target features, but recent studies suggest that target representations may shift "off veridical" from actual target features to increase target-to-distractor distinctiveness. However, these studies have been limited to simple visual features (e.g., orientation, color), which leaves open the question of whether similar principles apply to complex stimuli, such as a face depicting an emotion, the perception of which is known to be shaped by conceptual knowledge. In three studies, we find confirmatory evidence for the hypothesis that attention modulates the representation of an emotional face to increase target-to-distractor distinctiveness. This occurs over-and-above strong pre-existing conceptual and perceptual biases in the representation of individual faces. The results are consistent with the view that visual search accuracy is determined by the representational distance between the target template in memory and distractor information in the environment, not the veridical target and distractor features.