Constancy of attentional resources in processing cognitive tasks.

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This research were undertaken in order to determine whether the amount of attentional resources in processing a visual information remain constant for each subject, even when allocation of attention was changed by varying the visual targets in number, or the probabilities of their presentation. Reaction time to a target letter was used as the measure of resourses allocated to it.In the first experiment, one of the target letters were presented in a position of horizontal or vertical directions in the visual field, and subjects were told vocally to react to the targets. Performances were found to decrease as the directional separation, in which targets were presented, increased in number from one to four. When the probabilities of presentation for the letters were varied with the directions, performance for higher-probability direction increased, and performance for other direction decreased, in comparison with conditions in which the probabilities of each direction were equal.The objective of the second experiment was to examine more closely the assumption of the constancy of resources, under the conditions that one of the target letters presented in the center of the visual field. In the equal-probability condition, performance for each letter increased as the number of letters used increased from one to four. Increased probability for one letter improved performance on it, but reduced the resources available for other letters, in comparison with equal-probability condition.These experiments have revealed that there is a limit in ability of processing visual information, and the amount of attentional resources allocated to processing each target remains constant for each subject.