Spatial Frequency and Interference Between Global and Local Levels of Structure

In three experiments, subjects identified local or global forms of hierarchical stimuli that had been “contrast-balanced”. Contrast balancing eliminates low spatial frequencies, so that both local and global forms must be identified based on high-spatial-frequency information. In all three experiments, response times (RTs) to global forms were slowed for contrast-balanced stimuli, suggesting that low spatial frequencies facilitate the analysis of global forms. In contrast, interference between local and global forms was little affected by contrast balancing, suggesting that interference does not depend on differences in spatial frequency between local and global forms. Consistent with earlier data, some evidence of a difference in interference for stimuli presented in the right versus left visual field was found. However, this difference was not affected by contrast balancing—a finding that is at odds with the hypothesis that the hemifield asymmetry in interference reflects a hemispheric difference in inhibitory interactions between high and low spatial frequency channels.