Basic and Superordinate Image Categorization. Influences of the Extent of Congruence and the Time Parameters of Presentation of the Preceding Stimulus

Studies using a direct masking model addressed the influences of the time characteristics of masker presentation on the performance of basic and superordinate categorization (BC and SC) of images of objects in healthy young subjects. Maskers could be congruent, incongruent, or semantically neutral with respect to the target image. The first series analyzed the effect of asynchrony in the onset of stimulus presentation (stimulus onset asynchrony, SOA, i.e., the time interval between the onset of masker and stimulus presentations), which varied from 100 to 350 msec in 50-msec steps with a constant masker duration of 100 msec. The second series analyzed the effect of masker duration, which increased from 100 to 250 msec in steps of 50 msec with a constant SOA of 250 msec. SC was found to occur faster than BC. This is presumptively due to the participation of the low-frequency component of the stimulus description in SC, this component being transmitted rapidly via the magnocellular visual pathway. BC was more sensitive than SC to the temporal characteristics of the masker and its categorical affiliation. Furthermore, changes in SOA had a greater effect than masker duration on reaction time. If we accept the suggestion that changes in SOA influence the early perceptual stage of stimulus processing, then its sensitivity to unimportant information is apparent as a stronger dependence of BC than SC on SOA.