EFFECTS OF CONDITIONED REINFORCEMENT FREQUENCY IN AN INTERMITTENT FREE‐FEEDING SITUATION^1,2

Abstract

Key-pecking intermittently produced a set of brief exteroceptive stimulus changes under two-component multiple schedules of conditioned reinforcement. Throughout the study, free access to grain was concurrently provided on an intermittent basis via a variable-interval tape. Free food presentations scheduled by the tape were delivered if no peck had been emitted for 6 sec, and the brief stimulus changes produced by responding under the multiple schedules were those which accompanied food presentation. The second component of each multiple schedule was always associated with a 1-min, variable-interval schedule of conditioned reinforcement. The schedule associated with the first component was systematically varied and conditioned reinforcement was either absent (extinction) or programmed on a 1-, 3-, 6-, or 12-min variable-interval schedule. Under these conditions, rate of responding in the manipulated component decreased monotonically with a decrease in the frequency of conditioned reinforcement. In addition, contrast effects were often obtained in the constant, second component. These results are similar to those obtained with similar multiple schedules of primary reinforcement.In their review of positive conditioned reinforcement, Kelleher and Gollub (1962) suggested and gave many illustrations of an experimental approach involving the study of conditioned reinforcement under conditions in which primary reinforcement is not removed from the experimental situation. This approach involves the application of chained schedules of reinforcement and related procedures. In a chained schedule, responding in the presence of a given exteroceptive stimulus is reinforced on a given schedule with a subsequent exteroceptive stimulus. A chained schedule can involve any number of exteroceptive stimuli, each one of which is correlated with a given member or component. Since primary reinforcement terminates the schedule, and since each of the other exteroceptive stimuli in the chain can potentially serve as a conditioned reinforcer for behavior in the respective preceding member, chained schedules can be employed to assess the con-

Conditioned Reinforcement: Experimental and Theoretical Issues

“…Although some of the classic demonstrations ofconditioned reinforcement (e.g., Skinner, 1938;Zimmerman et al, 1967) lack the necessary control conditions to be interpreted unambiguously, subsequent work generally supports the generality of their findings. On the other hand, some of the major procedures still used to study conditioned reinforcement (e.g., second-order schedules) suffer from significant ambiguities of interpretation, and procedures that for the most part provide strong evidence for the concept (e.g., observing responses) have complexities that are not yet understood (which may eventually cause a rethinking of the role of conditioned reinforcement in these procedures).…”

“…This general approach was pioneered in a series of experiments by Zimmerman and his collaborators over the period of 1959 to 1967, and will be exemplified here by a description of one of their later studies (Zimmerman, Hanford, & Brown, 1967 Rashotte et al (1981) was the rate of pecking during S2 and how that behavior was affected by the schedule ofS2-S 1 pairings. They noted that the acquisition of pecking to S2 was a function of the number of pairings between S2 and S l, regardless of the percentage of S2 presentations followed by S 1.…”

Stimulus devaluation and extinction of chain schedule performance

“…In most instrumental learning situations, substantial stimulus change precedes the presentation ofthe primary reinforcer (e.g., the illumination and sound of food-hopper activation), and it is possible that the behavior is substantially under the control of these stimuli (cf. Zimmerman, Hanford, & Brown, 1967). Given such control by stimuli intervening between the operant response and primary reinforcer, it seems plausible that operant behavior trained even with simple reinforcement contingencies might be impervious to modifications of the current value of the primary reward, as with the chainschedules studied here.…”

Second‐order Schedules and the Problem of Conditioned Reinforcement

“…To speak of all paired and nonp?fred stimuli as conditioned reinforcers, however, presents some problems. Some experiments, not involving second-order schedules, have shown differences between paired and nonpaired procedures (Clark and Sherman, 1970;Sclhuster, 1969;Thomas, 1969;Zimmerman, D. W., 1969;Zimmerman, J., 1969;Zimmerman and Hanford, 1966;Zimmerman, Hanford, and Brown, 1967 (1968) of schedules of shock presentation (see also Morse and Kelleher, 1966). Under certain conditions, schedule performance when responses produce shocks is similar to that normally observed when responses produce food (Byrd, 1969;Kelleher and Morse, 1968;McKearney, 1968;1970a).…”