The Role of Spatial Frequency Selection in Local versus Global Perception
The aim of this research is to investigate the extent to which selective attention to spatial frequency (SF) mediates local versus global perception in general and in the context of face perception. Previous research has suggested a relationship between processing high versus low SFs and local versus global perception, respectively, but the nature of this relationship is debated. The experiments reported here demonstrate that attention to local and global aspects of a hierarchical display biases the flexible selection of relatively higher and relatively lower SFs during image processing. Moreover, the attentional selection of relative SF mediates the perceptual integration of the identity of elements in a hierarchical display with the level (local/global) at which they occur. Finally, the attentional selection of SF is shown to modulate early stages of face perception reflected in the N170-effect, a neurobiological index of face categorization that is particularly sensitive to face features. The N170-effect is found to be equally robust in response to the selection of both HSFs and LSFs in face-related stimuli, but the reliance on one SF scale or another is contingent upon the nature of the attended face-related stimulus, and whether its configuration is intact. Taken together, this investigation provides clear evidence that the flexible, top-down selection of low-level SF channels mediates the perception of local and global elements of visual displays, both for tightly controlled experimental stimuli as well as faces, a natural and frequently viewed hierarchical object category.