The Representation of the Stimulus in Character Classification
MICHIGAN UNIV ANN ARBOR HUMAN PERFORMANCE CENTER
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In the character classification task, the S is required to press one of two response keys to indicate whether or not the stimulus character is a member of a previously memorized set of characters. Reaction time RT in this task has been found to be a linear increasing function of the number of characters in the memorized set. It has been inferred from this result that part of the RT is occupied by a serial comparison stage in which an internal representation of the stimulus is compared with similar representations of the memorized characters. The study was designed to determine the nature of the representations that are compared. Upper and lower case letters were used as stimuli. In the Physical Identity Condition, S was required to respond on the basis of physical identity of the stimulus with a member of the memorized set i.e., S gave the negative response unless the stimulus matched in both name and case with a member of the memorized set. In the Name Identity Condition, Ss response was based on name identity only case was irrelevant. In the Control Condition all of the letters were the same case. Performance in the Name Identity Condition was essentially the same as in the Control Condition. In the Physical Identity Condition, the rate of the serial search was substantially slower. These results indicate that Ss typically use a recoded representation of the stimulus a name, verbal label, or other abstraction rather than a purely sensory image for the comparison stage.