An attempt was made to modify heart rate by presenting the Ss: E1-visual feedback and model signals, E2-feedback signals, E3-model signals, or C-no signals as a control group (6 Ss in each group). Model signal was a weak light which flickered at the rate of 20% above or below the pre-stimulus base IBI. All groups were required to either raise or lower HR alternately and E1 group was instructed to synchronize the feedback signal with the model signal. Significant bidirectional HR changes were found in 3 experimental groups and most effective changes were obtained in E1 group. In the second study, extended training to one S with E1 condition resulted in HR increases of 16 bpm and decreases of 9 bpm.