Date of Award


Document Type


Degree Name

Master of Arts (MA)




Although both theoretical and clinical issues are being investigated in the area of biofeedback, the need for the delineation of the potent variables is evident. Research must be designed to separate out the nonspecific placebo factors which are involved in biofeedback procedures. The present study incorporates a 2 x 2 x 2 factorial design to investigate the effects of two placebo variables--"expectancy of gain" and an apparatus placebo--on an electromyogram (EMG) feedback task.

Each of the forty-eight male undergraduate subjects had baseline EMG frontalis levels recorded. Two baseline periods were utilized to assess the before and after effe cts of the introduction of the inde- pendent variables. Each subject then received two twelve minute EMG feedback training sessions. The apparatus condition involved the pres- ence or absence of additional, n onessential equipment. The expectancy condition involved the presence or absence of positive information con- cerning the efficacy of feedback and benefits to be gained. The depen- dent measures included the EMG r ecording of the frontalis muscle poten- tial during baseline and trainin g sessions along with a post-session questionnaire used to assess sub ject expectancy and perception of the experimenter.

The results demonstrated a significant but paradoxical apparatus effect in that those subjects Who did not receive the placebo apparatus had significantly lower EMG levels. The importance of interpersonal relations was also indicated as subjects who perceived the experimenter as friendly and concerned tended to have lower EMG levels. The nonsignificant expectancy effect was dfLscussed in terms of the effect of prior knowledge of feedback. The importance of baseline measurements was also discussed in terms of length of baseline periods and the use of baselines for covariate adjustment.