THE ROLE OF SPATIAL-FREQUENCY IN THE PROCESSING OF HIERARCHICALLY ORGANIZED STIMULI

Can spatial frequency differences between local and global forms accou nt for differences in the way different levels of structure are analyz ed? We examined this question by having subjects identify local or glo bal forms of hierarchical stimuli that had been contrast balanced. Con trast balancing eliminates low spatial frequencies, so that both local and global forms must be identified on the basis of high spatial freq uency information. Response times (RTs) to global (but not local) form s were slowed for contrast-balanced stimuli, suggesting that low spati al frequencies mediate the global RT advantage typically found. In con trast, interference between local and global forms was little affected by contrast balancing or by shifts of attention between local and glo bal forms, suggesting that it does not result from inhibitory interact ions between spatial frequency channels or from temporal precedence of low versus high spatial frequency information. Finally, shifts of att ention between local and global forms were also little affected by con trast balancing, suggesting that they were not based on spatial freque ncy.