Discrimination without awareness in a psychophysical task
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Discrimination without awareness of the stimuli being responded to has been observed in a number of different experimental situations. In the classic case, the subject is instructed to relax or to engage in what is essentially a task of imagination, while incidental stimulation is presented at a level of intensity or duration such that he remains unaware of its presence. Responses of some comparatively unrestricted type are collected and analyzed for effects attributable to the stimulation. Present interest is in the case where the subject is effortfully attending to an objective task of discrimination. His range of possible responses to the task is quite narrow, and he is required to respond almost at once. The incidentally supplied stimulation is of a novel class, different from the stimulus material of the attended task; it is such as to present directly one of the possible task responses. The method used was an adaptation of a psychophysical judgment procedure, with individual subjects viewing the materials in a tachistoscope. A rectangular patch of standard size was presented first, followed in a few seconds by a test patch of variable size; the subject was required to report whether the latter was greater or smaller than the standard. A brief, unnoticed flash preceding the test patch carried the word greater or smaller or a nonsense control stimulus. A first experiment, using only three subjects, failed to yield any evidence of influence upon the judgments due to the unnoticed incidental words. In the second experiment, 32 subjects participated. The duration of the incidental flash waa gradually increased until the subject reported noticing its presence. Statistical analysis was restricted to the last 40 responses obtained at duration levels lower than the level at which recognition occurred. For the test patch of the same size as the standard (which had been presented on 24 of the 40 trials), it was clear that some subjects had indeed been influenced in the direction of agreeing with the unnoticed greater or smaller. The effect was statistically significant over all 32 subjects. About ten achieved a high degree of agreement with the incidental word, while the agreement scores of the others were distributed in approximately a chance fashion. Agreement was not influenced by sex of the subject. Four other test patches were of sizes greater or smaller than the standard. For two of these patches, subjects responded more accurately following the appropriate flash of greater or smaller than following the nonsense flash. No consistent relationships were found between latency of responding and agreement with the flashed stimulus. It is concluded from the main result that attended judgments of objective matters are (among some individuals) subject to influence from unreportable stimulation which directly presents the response to be used. This implies some necessary modification or extension of remarks made by Klein and others relative to this point. While attention usually acts to exclude activations which would be consciously rejected as inappropriate, such activations do (among some individuals) in a significant number of cases influence attended behavior without becoming conscious. A tentative conceptualization of the process is presented, based on psychoanalytic considerations by Kris and Fisher.
Thesis (Ph.D.)--Boston University.
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