Specification of the stimulus-reinforcer relation in multiple schedules: Delay and probability of reinforcement

Abstract

Control of pigeons' keypecking by a stimulus-reinforcer contingency was investigated in the context of a four-component multiple schedule. In each of three experiments, pigeons were exposed to a schedule consisting of two two-component sequences. Discriminative stimuli identifying each sequence were present only in Component 1, which was 4, 6, or 8 sec in duration, whilereinforcerscould be earned only in Component 2 (30 sec in duration). Control by a stimulusreinforcer contingency was sought during Component 1 by arranging a differential relation between Component 1 cues and schedule of reinforcement in Component 2. In Experiment 1, rate of keypecking during Component 1 varied with the presence and absence of a stimulus-reinforcer contingency. When a contingency was introduced, rate of keypecking increased during the Component 1 cue associated with the availability of reinforcement in Component 2. In Experiment 2, the stimulus-reinforcer contingency was manipulated parametrically by varying the correlation between Component 1 cues and Component 2 schedules of reinforcement. Responding in Component 1 varied as a function of strength of the stimulus-reinforcer contingency. The relatively high rates of Component 1 responding observed in Experiments 1 and 2 pose difficulties for conceptions of stimulus-reinforcer control based on probability of reinforcement. In these two experiments, the stimulus-associated probabilities of reinforcement in Component 1 were invariant at zero. An alternate dimension of stimulus-reinforcer control was explored in Experiment 3, in which Component 1 cues were differentially associated with delay to reinforcement in Component 2, while probability of reinforcement was held constant across components. When the stimulus-reinforcer contingency was in force, rate of responding in Component 1 varied inversely with delay to reinforcement in Component 2. In a quantitative analysis of data from Experiments 2 and 3, relative rate of responding during Component 1 was strongly correlated with two measures of relative delay to reinforcement.The acquisition and maintenance of keypecking in pigeons under autoshaping procedures (Brown & Jenkins, 1968; Williams & Williams, 1969) suggest that responses sensitive to operant contingencies can also be controlled by a stimulus-reinforcer (S-SR) contingency. Subsequent to this early work, many studies have been reported in which keypecking was shown to vary when some dimension of S-SR relation was changed (e.g., Gamzu & Schwartz, 1973; Garnzu & Williams, 1971, 1973Gibbon, Locurto, & Terrace, 1975;Hemmes, 1973). An issue which is becoming increasingly evident in this literature is a lack of consensus on the manner in which the S-SR relation is specified. Gamzu and Schwartz (1973), for example, reported that rate of keypecking under a responseindependent multiple schedule varied with relative rate of stimulus-associated food presentation.Thisresearch wassupportedby PSC/BHE Grant 13015 and by NIH Grant RR07064 to the first two authors. We wish to thank ElkanGa...

Pavlovian contingencies and anticipatory contrast

“…But this cannot be the critical difference because an autoshaping effect has in fact been demonstrated by Brown, Hemmes, Coleman, Hassin, and Goldhammer (1982), using a procedure quite similar to that for anticipatory contrast. In their study, different colored keylights were presented for 8-sec durations, and were then followed by 30 sec of a white keylight.…”

“…The issue raised is why a signal leading to a higher reinforcement rate produces excitation in the autoshaping procedure but response suppression in the contrast procedure. In the present study, this issue was addressed by systematically examining the role of two of the procedural differences between the previous contrast procedures (e.g., Williams, 1979) and the autoshaping procedures used by Brown et al (1982). In the latter procedure, the duration of the target stimuli was much shorter than the period of the following schedule, which should be expected to amplify the "predictiveness" of the target stimuli for the following reinforcement conditions.…”

“…But such a predictive relation has been used in other procedures to generate autoshaping (Brown & Jenkins, 1968). That is, the keylight that predicts the following higher rate of reinforcement should elicit higher response rates, which should result in the opposite of the contrast effects actually obtained.A major difference between the Pavlovian contingencies embedded in the anticipatory-contrast procedure and the usual autoshaping procedure is that the target stimuli in the former procedure do not lead directly to food, but lead Hassin, and Goldhammer (1982), using a procedure quite similar to that for anticipatory contrast. In their study, different colored keylights were presented for 8-sec durations, and were then followed by 30 sec of a white keylight.…”

“…A major difference between the Pavlovian contingencies embedded in the anticipatory-contrast procedure and the usual autoshaping procedure is that the target stimuli in the former procedure do not lead directly to food, but lead Hassin, and Goldhammer (1982), using a procedure quite similar to that for anticipatory contrast. In their study, different colored keylights were presented for 8-sec durations, and were then followed by 30 sec of a white keylight.…”

Escape From Serial Stimuli Leading to Food

“…In Pavlovian conditioning, to be sure, it is well known that the effectiveness of the conditional stimulus (CS) is a function of the length of time by which it has characteristically preceded the unconditional stimulus (US), but Balsam, 1984;Brown, Hemmes, Coleman, Hassin, & Goldhammer, 1982;Gibbon & Balsam, 1981;Jenkins, 1984;Jenkins, Barnes, & Barrera, 1981;Jenkins & Shattuck, 1981. ) As mentioned earlier, under standard Pavlovian procedures stimuli that are negatively correlated or that precede the US by longer than average times are found to be inhibitory (LoLordo & Fairless, 1985;Rescorla, 1969b).…”