The Effects of Fixed Ratio and Contingent Time on Human Lever-Pressing Behavior

Fixed ratio (FR), the schedule requirement on the instrumental response, and contingent time (CT), the amount of time the reinforcing response was available, were investigated in a human lever-pressing situation. Two levers, one programmed on a CRF schedule, and one on an FR schedule, produced the same reinforcer, points on a counter. Responding was more probable on the CRF lever when compared with the FR lever during baseline trials. In the contingency conditions, Ss were required to complete a requirement on the less probable instrumental response (FR lever) to gain access to the more probable reinforcing lever (CR lever). In Experiment I, increasing the amount of available CT (2, 5, 10, and 20 sec.) resulted in increased responding on the CRF lever and decreased responding on the FR lever. In Experiment II, increasing the FR requirements (FR 5, 10, 20, 40, and 80) resulted in less responding on the CRF lever and more responding on the FR lever. When CRF and FR lever presses were combined within each experiment, it was found that total responding was relatively constant across increases in the FR requirements and across increases in the amount of CT. This suggested that the effect of the two parameters under investigation is primarily upon the distribution of responses on the two levers and that the rate of responding is high and constant regardless of changes in the values of the parameters.