Effects of spatial frequency bands on perceptual decision: It is not the stimuli but the comparison

Are there optimal spatial frequencies for different perceptual decisions? We had observers perform 3 between- and 2 within-category perceptual decisions with hybrid stimuli comprising low and high SF images. Responses were to one SF band and the information carried by the other SF could be congruent (same category), incongruent (opposing category) or neutral to the response (either noise or a task-irrelevant stimulus category).Processing efficiency for the different SF bands varied across tasks, with house-flower, face-house and expression-valence decisions more efficient when based on high SF components, while flower-face and gender categorizations were more efficient when based on low SF components. In addition, there was asymmetrical interference from the more efficient SF components onto decisions based on the less efficient components. Strikingly, we also demonstrated that SF efficiency responses for identical hybrid stimuli were affected by the task context rather than the stimuli components. These results demonstrate that perceptual decisions are affected by an interaction between task and SF range; and that differences between task relevant categories determine the efficiency of one SF range for a given task. An exploration of the stimuli statistics aimed to reveal potential diagnostic attributes suggested that performance in the between-category tasks were associated with differences in orientations and overall energy levels at each SF band, while performance in within-category discriminations were associated with the number of visual features in each SF band. We conclude that the diagnostic values of each SF range can be associated to low level differences in visual features, and the larger these differences are the more efficient the perceptual decision.