Visual recognition as a joint function of induced effort and manifest anxiety
Shore, Milton Frank
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Efficiency of perceptual performance has been shown to be a function not only of stimulus variables such as size and shape, and physiological variables such as adaptation and visual acuity, but also of psychological variables such as effort and anxiety. Although there have been a large number of studies on the effect of these psychological variables on performance, the results have varied. Many theories have been proposed to explain the variety of results. Freeman has recently attempted to unify the contradictory results by a theory of energy mobilization and homeostasis. He has suggested that as the amount of energy mobilized in a task is increased, response efficiency is first facilitated until an optimum is reached. Beyond this optimum, an increase in energy mobilization produces a reduction in efficiency until inhibition of performance oecurs. Freeman's theory is based on two major hypotheses: 1. Efficiency is a function of the amount of energy mobilized at any given time. As energy is mobilized, efficiency first rises to an optimum, then falls until inhibition of performance results. (Freeman calls this the homeostatic response sequence curve) 2. The amount of energy mobilized at a given time is the sum of all activities mobilizing energy in the organism. (Summation hypothesis) These hypotheses were tested by presenting stimuli varying in difficulty and under various degrees of induced muscular effort to subjects differing in anxiety level. Three predictions were derived: 1. Starting from a point of zero induced effort, efficiency of visual recognition will rise to a maximum, then decline as the amount of induced effort increases. 2. The more difficult the recognition task, the less the amount of induced muscular effort needed to reach the point of maximum efficiency. 3. The point of maximum efficiency will occur under less induced effort in anxious than in non-anxious subjects. THE EXPERIMENT Selection of Subjects. The Spence-Taylor Manifest Anxiety Scale was used to classify the subjects into three anxiety groups. The Scale (Short Form) was administered to more than 300 university students. Eighteen subjects were selected for the experiment. There were six subjects in each of the three anxiety groups. Subjects with scores of 1-5 constituted the "low anxiety" group, those with scores of 13-15 the "medium anxiety" group, and those with scores of 24-28 the "high anxiety" group. All the subjects were male, right-handed, and had 20/20 visual acuity (corrected or uncorrected). Procedure. Ten common photographic resolution targets, five circular targets and five square targets, were presented randomly for recognition in an electronically-timed tachistoscope at the speeds of .002, .004, .006, .008, .010, .012, .014, and .016 seconds. The visual angle subtended was 17.9'. Fractions of the maximum pressures at the end of fifteen seconds of gripping on the Smedley hand dynamometer were used as the effort conditions. The conditions used were 0, 1/8, 1/4, 3/8, 1/2, and 3/4. The order of the effort conditions was counterbalanced in each group. When the subject pressed the dynamometer with his left hand to the value set for the day, the target was exposed. The subject was asked to describe what he saw. RESULTS Prediction 1. The overall relationship between effort and visual recognition was in the direction predicted. The pooled results for the three groups showed a rise in the number of targets correctly identified until the maximum was reached at 1/4. Beyond 1/4, an increase in muscular effort resulted in a gradual drop in efficiency with performance at the 3/4 level not significantly different from the performance under no induced effort. An analysis of variance of this curve showed a deviation from a straight line which was significant beyond the .01 level. Prediction 2. The definition of target difficulty used in this study was in terms of the performance at the Observation level. Those targets with low recognition scores under no induced effort were considered more difficult. Square Targets, therefore, were consistently more difficult than circular targets. An analysis of variance revealed no significant difference in the effect of induced effort on targets varying in difficulty. However, when the performance of the three anxiety groups on square and circular targets was compared, the performance of the "low anxiety" group was in the predicted direction. The effect of difficulty appears to be a function of its interaction with anxiety and induced effort. Further research will be neceasary to determine the nature of this interaction. Prediction 3. The results were opposite to prediction three. Although there was no significant difference between the performance of the three anxiety groups under no induced effort, the "high anxiety" group improved in efficiency as effort increased, and remained at a highly efficient point even at the 3/4 level. The "medium" anxiety" group, following the pooled curve, rose as effort increased, then fell with performance at the 3/4 level not significantly different from the performance under no induced effort. The "low anxiety" group rose only slightly, and fell below the performance at the Observation level. A trend analysis of the curves for the three anxiety groups was significant beyond the .01 level. DISCUSSION In the present experiment, while Freeman's theory predicted the overall relationship between energy mobilization and the efficiency of performance, as well as the performance of the "medium anxiety" group, the results of the "low anxiety" and the "high anxiety" groups were inconsistent with his theory. It was suggested that Freeman's theory of energy mobilization could not adequately handle the concept of anxiety. An explanation of these results has been suggested by some recent studies. They suggest that three factors should be considered in predicting performance in a given situation. First, the anxiety level of the subject should be evaluated. The second factor is an evaluation of the nature of the task. The third factor is the manner in which the person handles threatening stimuli and situations of stress. It was suggested that as induced effort increased and the task became more stressful, the subjects employed the characteristic adjustive mechanisms they use in threatening situations. Thus those subjects who denied anxiety in the self-report anxiety scale blocked out more of the environment as stress increased, while those subjects who were hypersensitive to anxiety symptoms were more sensitive ("vigilant") to the environment with an increase in stress.
Thesis (Ph.D.)--Boston University
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