In the first of two studies, subjects (Ss) were required to either raise or lower heart rate (HR) relative to pre‐trial baseline by altering a tone which changed frequency with HR. Reliable increases but no decreases in HR were found. In a second study extended training of a single S with visual feedback resulted in consistent sustained HR increases of 15 to 35 beats per minute (bpm), but only slight decreases. Sustained elevated rate was accompanied by anxiety. No reliable changes in breathing occurred in either study.

Three groups of human 5"s were given differential conditioning trials with respiration uncontrolled, controlled at normal rates, or controlled at rapid rates. Significant differential heart rate responding occurred in all groups and, except in the rapid breathing group, improved across trials. Respiration did not affect the form of the conditioned response.There were three significant components: deceleration immediately following CS onset, subsequent brief acceleration, and marked deceleration just prior to UCS onset. Analysis indicated that the triphasic response was neither a homeostatic adjustment nor an unconditioned orienting response (OR). Discrepant findings in earlier studies may be largely explained by experimental conditions that differentially affect the three components.

Thirteen human subjects (Ss) were given immediate auditory feedback concerning their salivary rates and were asked both to increase and to decrease their rates during a series of 30‐sec trials. Significant decreases, but not increases, in salivary rate were obtained relative to baseline. During the second half of the experiment, when feedback was omitted until the end of each trial, Ss maintained significant differential response rates between increase and decrease trials, but the reliability of decreases from expected baseline was reduced. Thirteen control Ss, who received feedback only at the end of each trial during both halves of the experiment, were unable to alter their rates during either half. Salivation on increase and decrease trials was not systematically correlated with changes in either heart rate or breathing rate in the immediate feedback group.