No abstract

The responses of five pigeons were reinforced on concurrent variable-interval variableinterval reinforcement schedules in which changeover key responses changed the stimulus and reinforcement schedules associated with the food key. While the reinforcement availability in one component remained unchanged throughout the experiment, the reinforcement availability in the other component was, during several conditions, signalled by the onset of an additional discriminative stimulus. During unsignalled conditions, both the relative frequency of responding and the relative time spent in each component approximated the obtained relative reinforcement frequency in each component. The effect of signalling reinforcer availability in one component was to (1) reduce responding in the signalled component to near-zero levels, and (2) increase the relative time in the unsignalled component, without a corresponding increase in the obtained relative reinforcement frequency. The magnitude of the increase in relative time in the unsignalled component decreased as the overall frequency of reinforcement increased. This deviation in the matching relation between relative time and the obtained relative reinforcement frequency was eliminated if the overall reinforcement frequency was increased before the signal was introduced and then, without removing the signal, gradually reduced.

No abstract

Thresholds for rat and human Ss were estimated from discrimination gradients using conditioning procedures which were similar for both species. Measures of sensitivity to changes in the rate of audible click presentations were obtained for repetition rates from 10-80 clicks per second. Marked agreement between the species was found for all test points except 80 pps. The possibility of a species difference in the perceptual basis of discrimination at 80 pps is discussed.

No abstract