AFTEREFFECTS OF REINFORCEMENT ON VARIABLE‐RATIO SCHEDULES¹

Abstract

On each of variable-ratio 10, 40, and 80 schedules of reinforcement, when rats' leverpressing rates were stable, the concentration of a liquid reinforcer was varied within sessions. The duration of the postreinforcement pause was an increasing function of the reinforcer concentration, this effect being more marked the higher the schedule parameter. The running rate, calculated by excluding the postreinforcement pause, was unaffected by concentrationi. The duration of the postreinforcement pause increased with the schedule parameter, but the proportion of the interreinforcement interval taken up by the pause decreased. Consequently, the overall response rate was an increasing function of the schedule parameter; i.e., it was inversely related to reinforcement frequency, contrary to the law of effect. The runining rate, however, decreased with the reinforcement frequency, in accord with the law of effect. When 50% of reinforcements were randomly omitted, the postomission pause was shorter than the postreinforcement pause, but the running rate of responses was not affected.Key words: reinforcement magnitude, postreinforcement pause, running rate, reinforcement omission, law of effect, variable ratio, rats It is an almost universal phenomenon that the presentation of a reinforcing stimulus is followed by a pause in responding. Given that the reinforcer is a food substance this is not surprising, since for a period after reinforcement the subject is occupied in consummatory activity. In many schedules, however, the postreinforcement pause is longer than the time taken to consume the reinforcer. Moreover, on several sclhedules of reinforcement, the duration of the postreinforcement pause is affected by variables other than time taken to eat. For example, on a fixed-interval (FI) schedule, it is an increasing function of the duration of the fixed interval (Schneider, 1969;Sherman, 1959), and of the concentration of a liquid reinforcer when the amount is held constant (Lowe, Davey, and Harzem, 1974).One explanation of this phenomenon is that the reinforcer functions as a discriminative stimulus, signalling the start of a period in whiclh reinforcement is not available (Ferster 'These data form part of a doctoral dissertation submitted to the

The Measurement and Functional Properties of Reinforcer Value in Single-Alternative Responding: A Test of Linear System Theory

“…These findings are consistent with some previous studies (Bradshaw et aI., 1978;McDowell & Wood, 1984, but inconsistent with several other studies (Cheeta, Brooks, & Willner, 1995;Phillips, Willner, & Muscat, 1991a, 1991Priddle-Higson, Lowe, & Harzem, 1976;Reed, 1991). Indeed, the function describing the relation between reinforcer magnitude and response rate has been variously described as increasing, decreasing, monotonic, bitonic, or flat (Bonem & Crossman, 1988;DeGrandpre, Bickel, Hughes, & Badger, 1993).…”

The Application of the Matching Law to Simple Ratio Schedules

“…Increases in the size of variable-and random-ratio schedules appear to produce changes similar to those that occur in the fixed-ratio case, though the relation is not always as marked (eg., Brandauer, 1958;Kelly, 1974;Priddle-Higson, Lowe, and Harzem, 1976 2Equation (1) is interpretable only if R,, P, and k 0, and n > 0. A plausible interpretation of n = 0 is that no schedule is in effect and the reinforcer is continuously and freely available to the subject.…”

“…In the case of Equation 1, it is not clear that there exists a generally appropriate combination of rationale and data. The strongest justification for the use of running rate is that, of all rate measures, it comes closest to showing a direct relation between responding and frequency of reward (Priddle-Higson et al, 1976). Neither this rationale nor the fit to data reviewed above appears to preclude the active consideration of rate measures other than the running rate.…”

A Comparison of Response Patterns on Fixed‐, Variable‐, and Random‐ratio Schedules

“…Priddle-Higson, Lowe, and Harzem (1976) examined changes in reinforcer magnitude and changes in VR size. They found a decrease in PRP and an increase in overall response rate (including the PRP) as VR size was increased from VR 10 to VR 40 to VR 80.…”