TACHISTOSCOPIC THRESHOLDS AND INTENSITY-TIME FUNCTIONS USING PATTERN STIMULI IN MONKEYS AND HUMANS.
Item
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Title
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TACHISTOSCOPIC THRESHOLDS AND INTENSITY-TIME FUNCTIONS USING PATTERN STIMULI IN MONKEYS AND HUMANS.
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Identifier
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AAI8302510
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identifier
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8302510
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Creator
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GLOVER, ANDREW ARTHUR.
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Contributor
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Pedro Pasik
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Date
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1982
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Physiological
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Abstract
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In this investigation, tachistoscopic thresholds for pattern stimuli as well as intensity-time functions are obtained for monkeys and human observers at several luminance levels. The stmuli are simultaneously presented triangle-circle pairs. Subjects initiate their own trials and are required to respond during each trial.;In Experiment I, thresholds are obtained for monkeys using the descending staircase procedure as well as the method of constant stimuli. Two levels of luminance are used. For each level, adapting and simulus fields are flux-equated. Psychometric functions are constructed from the constant stimuli data. Threshold values, as well as energy required at threshold, are comparable across methods. Attenuating the luminance by 1.2 log units results in an increase of threshold duration, but of only 0.4 log units magnitude. In addition, less energy is required at threshold for the lower values of luminance. Qualitative observations in a human subject are consistent with these findings. The results indicate that duration plays a more significant role than intensity for obtaining the criterion response, which suggests a supersummation effect.;In Experiment II, thresholds are obtained for three monkeys and one other human subject using only the descending staircase procedure. Eight stimulus luminances are used at a constant light adaptation level. Stimulus and adapting fields are flux-equated only in the condition utilizing the highest luminance. The other several levels are attenuated in 0.3 log steps. Intensity-time functions are constructed from these data. Slopes of these functions are steeper than -1.0, again indicating supersummation, i.e., duration is more effective than intensity in eliciting the criterion response. Function analyses show a region of reciprocity at briefer durations followed by supersummation. Response latency values remain relatively constant for stimuli of high luminance and brief duration, and become progressively longer at lower luminances and longer durations. Similarly, the stimulus energy at threshold results in comparable latencies at higher levels, and an increment in latency at lower levels.;The results of both Experiments I and II indicate that duration is more effective than luminance for a threshold pattern discrimination task, i.e., supersummation is demonstrated in both studies. The magnitude of the phenomenon is not the same across experiments, indicating that the level of light adaptation may have an effect.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Psychology
