Temporal Effects of Complex Discriminations

Abstract

Since the formulation of the personal equation, reports of reaction time experiments have appeared consistently in the literature. A large number of extraneous variables have been manipulated to determine their effects on reaction time. Among these are the sense modality stimulated, the intensity and duration of the stimulus, the number of receptors stimulated, age, sex, preparatory set, drugs, physical state, and various environmental conditions. A number of these investigations attempted to evaluate aspects of the central nervous system by comparing differences in RT for the different sensory organs. The results are inconsistent due to the difficulty in equating the intensity of the stimuli. These investigations point to the possibility that differences in RT might be related to the complexity of the discriminations required, although the stimulus and response were not varied. With the latter variables held constant, differences in RT due to more complex discriminations might reflect the temporal aspects of making discriminations. This investigation was designed to study the temporal effects of S's making increasingly more complex discriminations. PROCEDURE The apparatus was designed to permit responses in modalities, manual and verbal. A gray panel on which three lights were mounted triangularly with the apex pointing down provided the stimuli. Responses were made on telegraph keys, mounted 2 in. apart, or via a microphone. S was instructed that the top lights indicated the response to make while the light at the apex indicated the modality in which to make the response. When the apex light was on, a verbal response was required; and when the apex light was off, a manual response was required. The manual response was pressing either the left or right telegraph key and the verbal response was one or two for the left and right stimulus lights, respectively. A .001-min. timer started simultaneously when the stimulus light was rurned on and stopped when the correct response was made. Three levels of response complexity were tested. Firsr, simple RT for each modality was determined by informing S of the response that was required as soon as the stimulus light came on. The next level was defined as discrimination RT within each modality. S was informed of the modality in which the response was to be made but not which of the rwo alternative responses to make, either left or right key pressing, or one or two,