Interaction of procedural factors in human performance on yoked schedules.

The differential effects of reinforcement contingencies and contextual variables on human performance were investigated in two experiments. In Experiment 1, adult human subjects operated a joystick in a video game in which the destruction of targets was arranged according to a yoked variable-ratio variable-interval schedule of reinforcement. Three variables were examined across 12 conditions: verbal instructions, shaping, and the use of a consummatory response following reinforcement (i.e., depositing a coin into a bank). Behavior was most responsive to the reinforcement contingencies when the consummatory response was available, responding was established by shaping, and subjects received minimal verbal instructions about their task. The responsiveness of variable-interval subjects' behavior varied more than that of variable-ratio subjects when these contextual factors were altered. Experiment 2 examined resistance to instructional control under the same yoked-schedules design. Conditions varied in terms of the validity of instructions. Performance on variable-ratio schedules was more resistant to instructional control than that on variable-interval schedules.

Ventricular ectopy frequency and complexity not altered by exercise training in coronary disease patients.

To assess the effect of exercise training on ventricular ectopy in coronary artery disease patients, 21 patients with coronary disease had 24-hour ambulatory electrocardiograph recordings done at entry into a cardiac rehabilitation program and after 6 months' exercise training. Mean frequency of premature ventricular contractions was not significantly changed, being 9.7 +/- 33.0/h before and 13.2 +/- 94.3/h after training. 9 demonstrated an increased, 9 a decreased, and 3 an unchanged frequency. Lown grade of ventricular ectopy was similarly not consistently changed with training.