Locus of control and expectancy in electromyographic biofeedback.

From a subject pool of 226 psychology students, 16 external and 16 internal subjects, as determined by the Nowicki-Strickland Locus of Control Scale, were randomly assigned to either a positive or a negative expectancy group (n = 8). In Session I all subjects were asked to relax their frontalis muscle using auditory proportional biofeedback over 8 subsequent 3-min trials. The procedure was repeated during Session II except for the inclusion of a verbal expectation which suggested subjects' likelihood or non-likelihood of achieving further muscle relaxation. Results indicated that externals with positive expectancy had significantly higher levels of tension than internals with positive expectancy. No difference between externals and internals in the negative expectancy condition were observed. Results are interpreted to indicate that cognitive set affected the perception of performance ability with externals being disrupted by comments suggesting positive expectancies.