The role of feedback in voluntary control of blood pressure in instructed subjects.

Forty normal male volunteers were randomly assigned to one of four experimental conditions and instructed to raise and lower their systolic blood pressure. Subjects received either beat-to-beat feedback contingent on pressure changes, noncontingent beat-to-beat feedback, noncontingent feedback presented randomly with respect to the occurrence of each heart beat, or instructions alone. The order of increase and decrease trial blocks was counterbalanced across groups. Subjects receiving contingent feedback were monetarily rewarded for appropriate pressure changes. Subjects receiving noncontingent feedback received rewards and feedback equal to the mean received by the contingent group. Subjects in the instructions-only condition were also paid this bonus but were informed of their earnings only at the conclusion of the experiment. Results indicated that in the presence of instructions, feedback, whether contingent or noncontingent, added little to subjects' ability to control pressure during a single session. Theoretical and clinical implications are discussed.