Psychosomatic Medicine 17:185-199 (1955)
© 1955 American Psychosomatic Society

Effect of Variations in Laboratory Procedure and Experimenter upon the Ballistocardiogram, Blood Pressure, and Heart Rate in Healthy Young Men

¹ Neuropsychiatry Division, Army Medical Service Graduate School, Walter Reed Army Medical Center, Washington, D.C.

Psychological and physiological (BCG, ECG, heart rate, and arterial blood pressure) responses to the stress associated with experimentation itself have been studied in 48 healthy young soldiers. Two clusters of variables (uncertainty as to the exact nature of the procedure, plus military rank, professional status, experience, and personality of the experimenter) have been separately and independently manipulated. Two "identical" experiments on comparable groups have been carried out; half the subjects were tested by a psychiatrist (Capt. M. C.--Experiment I), the other half by a physiologist (Pvt.--Experiment II). In each experiment, half the subjects (control subgroup) were reassured as to the benign nature of the procedure immediately upon entry to the laboratory, and half (experimental subgroup) were not given this information until a 10-minute interview which followed a rest period on the BCG table. Control subjects were also interviewed for a corresponding 10-minute period. All interviews were recorded on magnetic sound tape, and later were independently rated by three psychiatrists who did not know the physiological results at the time of the rating.

In each experiment, experimental and control subgroups could be distinguished on the basis of a statistically significant difference in the mean physiological response to the interview. However, in each experiment the discrimination was related to only one of the functions measured, and this single function differed with the experimenter--amplitude of the BCG in the experiment carried out by the medical officer; mean arterial blood pressure in the experiment carried out by the enlisted man. Appraisal of the sound records revealed a corresponding difference in the total psychological context of the two sets of interviews. These data suggested that the main emotional change during the experimental interviews in Experiment I was relief of uneasiness and tension, whereas the main emotional shift distinguishing the experimental subjects in Experiment II appeared to be the discharge or relief of angry resentful feelings.

The findings suggest that differences in the experimenter-subject relationship may alter the total meaning of the experimental situation so that different psychological and physiological mechanisms of response are evoked by an otherwise identical test procedure. The data are consistent with the concept that there may be specific qualitative as well as quantitative relationships between the psychological and physiological (circulatory) responses to stress.

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