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The effect of food deprivation on visual responding in humans
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|Title:||The effect of food deprivation on visual responding in humans|
|Authors:||Cole, Robert Eugene|
|Abstract:||Previous research indicates that a 14 hour food deprivation can significantly increase visual sensitivity as measured by absolute threshold and the effect of an inducing annulus on the brightness of a test field. The present study was designed to extend food deprivation time to 72 hours and include a number of physiological measures, along with visual sensitivity, as a function of deprivation time. A complete replication of the deprivation schedule was included to determine adaptation of both visual and physiological responses to food deprivation. Two groups of five subjects each were formed by random assignment from a group of ten male college students who had been judged medically fit to withstand the stress of the food deprivation schedule. One subject was eliminated from the Experimental group midway through the experiment because of illness. The Control group received a highly controlled maintenance diet of 2200 calories/day throughout the 22 day course of the experiment. The Experimental group, on the other hand, was fed on the following schedule: five days of maintenance diet, 72 hours of complete food deprivation, six days of maintenance diet, 72 hours of complete food deprivation, and five days of maintenance diet. With the exception of days 12 and 13, experimental sessions were held twice a day. In all sessions, three visual measures were taken using the method of adjustment: (a) absolute threshold (b) the brightness of a test field surrounded by a dimmer inducing annulus (enhancement), and (c) the brightness of a test field surrounded by a brighter inducing annulus (inhibition). Following each visual session, measures were taken of oral temperature, blood pressure, pulse rate and subjective ratings of hunger and fatigue. Additional measures on the same subjects included body weight, blood serum glucose and sodium levels, sodium and potassium excretion from the urine, and blood pressure and heart rate measured before, after and following recovery from five minutes of strenuous exercise. On each of the above measures subjects were equated statistically on the basis of predeprivation response levels. Group means calculated from the above values provided a measure of the mean amount of change across the feeding and deprivation schedule. The results of the visual measures showed significant group differences on threshold and inhibition change but not on enhancement change. The point at which the difference occurred, however, and the direction of the difference were completely unexpected. Both groups showed threshold decreases during the initial predeprivation period Which continued through the first deprivation period. The point of separation of the groups occurred with the resumption of feeding of the Experimental group where their threshold level increased to the initial predeprivation level and remained relatively stable through the second deprivation and recovery periods. The Control group, after its initial decrease in threshold, remained at a low threshold level throughout the remainder of the experiment. The inhibition results are similar to the threshold results. The physiological results showed changes consistent with the feeding and deprivation schedule. Oral temperature, systolic blood pressure, serum glucose and sodium levels, and urine sodium and potassium excretion decreased with hours of deprivation while diastolic blood pressure and activity state pulse rate increased. The Experimental group showed significant increases in ratings of hunger and fatigue in both deprivation periods o It was concluded that (a) the conditions of the present study resulted in significant differences in visual responding between food deprived and nondeprived groups; (b) the nature of the changes in visual responding, which are only partly accounted for by hours of food deprivation, suggest the presence of other variables of a more psychological nature; and (c) the visual changes are not directly related to changes in autonomic responding or to subjective ratings of hunger and fatigue. Possible reasons for the unpredicted changes in visual responding were discussed.|
Thesis (Ph. D.)--University of Hawaii, 1966.
Bibliography: leaves 81-83.
ix, 83 l illus., tables
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Ph.D. - Psychology|
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