Is stimulus structure in the Mind's eye? An examination of dimensional structure in iconic memory

Three experiments examined integral and separable dimensions as attentional selective cues from iconic memory. Sperling's partial-report task was employed with physically separable and physically integral stimuli. Stimulus displays were varied in terms of the redundancy of the irrelevant non-cued dimensions—i.e. control, correlated, and orthogonal conditions within Garner's (1974a) framework—and selective readout performance was measured. The results demonstrate that, in initial processing, physically separable dimensions (e.g., circle size vs. angle of radial line) can be selectively attended to as independent dimensions, but physically integral dimensions (e.g., size vs. brightness and height vs. width) can only be represented as wholistic integral objects. Implications of these findings for current models of feature integration and perceptual development are discussed.