Research has shown that reinforcer variety can increase response rates. To determine whether the reinforcers comprising this variety must differ in reinforcing strength in order to produce this effect, rats were trained to lever press under three reinforcement conditions: pellets-only, sucrose-only, and pellets or sucrose (varied reinforcement). Although the sucrose concentration was made to be roughly equivalent to the pellets in reinforcing strength, the varied-reinforcement still produced the highest response rate.Several studies have shown that varied reinforcement can produce higher response rates than comparable conditions in which this variety is lacking (e.g., Wunderlich, 1961;Steinman, 1966Steinman, , 1968. Although it has been demonstrated that this "variedreinforcement effect" can be obtained whether the comparisons are made between groups or between conditions within Ss, the basis for the effect is still unclear. In all of these experiments, the reinforcers used have not only differed in kind (providing variety in the stimulational characteristics of the reinforcers); they have also differed in reinforcing strength, i.e., the response rates that each of the reinforcers will produce when delivered separately differ from each otller.Thus, questions remain concerning the relative contribution of stimulational variety and variety in reinforcement strength in the production of the increased rates found ina varied-reinforcement procedure. The present experiment investigates the effect of varied reinforcement upon response rate when the reinforcers are similar in reinforcing strength. SubjectsTwelve experimentally naive male hooded rats of the Long-Evans strain served as Ss. When about 100 days of age they were placed on a food deprivation cycle permitting access to Purina Lab Chow for 1 h per day. Water was available ad lib. ApparatusTwo sound-restricted chambers contained a 13.5 x 7.5 in. Skinner box with a 2 in. wide metal lever on one wall and a 3.5 x 3 in. panel on the opposite wall. Behind the panel was an area for the delivery of 45 mg food pellets and a fountain device for the delivery of sucrose solution. All programming and recording equipment was automatic and inaudible to S. ProcedureSs were trained to press the lever, which on a variable interval (VI) schedule having a mean interval of 45 sec (VI 45) resulted in the onset of a 0.5 sec indicator light. Pushing the panel after the onset of the light produced a 45 mg food pellet.Psychon. Sci., 1968, Vol. 10 (I) WARREN M. STE~AN2 UNIVERSITY OF ILLINOISPhase 1. When the above behavioral chain had been established, a tone (T1) of either 400, 1900, or 4000 cps was presented for six 5 min periods within each session. Completed chains during T1 were reinforced with food pellets. At the end of a 5 min period the tone ceased and no further responding was reinforced. This time out from reinforcement (TO) continued until S refrained from lever pressing or panel pushing for a minimum of 15 sec, at which time T1 was reinstated. When for three consecutive ses...

Instructions, discrimination procedures, and sources of reinforcement were manipulated in order to determine the bases for the maintained "non-reinforced" imitations observed in generalized imitation research. Six girls received imitation training from two experimenters. One experimenter modelled only reinforced responses; the other modelled only non-reinforced responses. The children imitated all responses when no reinforced alternative was available, even though results of choice procedures and special instructions clearly demonstrated that they discriminated reinforced from non-reinforced responses. Instructions not to perform non-reinforced imitations immediately eliminated these behaviors. It is suggested that social setting events may be largely responsible for generalized imitation.

No abstract

No abstract

Twelve rats were trained to lever press on a multiple schedule with the delivery of pellets, sucrose, or pellets or sucrose correlated with the three legs of the schedule. The "pellet-orsucrose" condition, i.e., varied reinforcement, produced the highest response rates. These results replicate, in a within-Ss design, the previous findings of a between-group experiment.