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Abstract
The present study was designed to determine what types of stimulus input are required to make rapid category decisions. In 3 experiments, this question was addressed using ultra-rapid visual categorization (URVC) in conjunction with backward masking. The first experiment showed typical URVC accuracy with unmasked photographs of natural scenes and established masked categorization performance with these stimuli. Experiment 2 tested the hypothesis that line drawing information is sufficient to perform rapid categorizations. It was found that URVC accuracy was comparable, if not higher, with line drawings than photographs. The third experiment tested the hypothesis that a particular range of spatial frequency information is used in URVC. Results indicated participants were more accurate with low band passed than high passed scenes. Taken together, these results indicate high contrast, global form information may be necessary for URVC.