Motor Performance under Stress as a Function of the Amount of Practice

The effects of stress on performance are far from clear (Beam, 1955; Castanda & Lipsett, 1950; Farber & Spence, 1953). Stress has been shown to either improve or impair performance depending upon varying experimental conditions. Two factors that appear important in determining the effects of stress are the relative difficulry of the skill to be performed and the degree of proficiency in the skill when stress is inuoduced. Using a motor skill (balancing on a pivoted platform) that permitted the relative level of difficulty to be varied, Ryan (1961b) found that after 12 practice uials threat of electric shock had no deleterious effects on performance of an easier skill but impaired performance on a more difficult skill. Earlier Deese and Lazarus ( 1952 ), investigating the effects of failure-stress on rotary pursuit performance, found that stress introduced early produced a small decrement in performance, while failure-stress introduced late in learning produced a small facilitation. If the assumption can be made that skills become easier as learning progresses, these studies support each other. In Ryan's study stress had no effect on the easy skill but impaired the more difficult one. In the smdy by Deese and Lazarus stress had no effect on performance late in learning when the task would be assumed to be easiest, but early in learning when the task would be assumed ro be more difficult stress impaired performance. From chis it appears that the relative ease of performance may be a crucial factor in determining the effects of stress on performance, with stress having its most disruptive effect early in learning when performance appears most difficult, then becoming less disruptive as learning progresses. From this hypothesis the prediction would be that performance on the difficult motor skill used in the Ryan study (1961b) would not be expected to show the same deleterious effect under stress late in learning as it did earlier. METHOD Silbject~.-Ss were 40 male university students, all volunteers, from various areas of specialization. None had previous experience in performing similar tasks.