Four types of schedule interactions have been defined: positive contrast, negative contrast, positive induction, and negative induction. Most work has centered on the necessary conditions for positive contrast. One position states that a reduction in reinforcement frequency is necessary; the other view states that a reduction in response rate is necessary. Neither view can account for the occurrence of induction. The present experiment tests the hypothesis that stimulus control effects the occurrence of either contrast or induction. Three pigeons were trained to respond for primary reinforcement (strong stimulus control condition), and three pigeons were trained to respond for conditioned reinforcement (weak stimulus control condition). A response rate decrease was caused by changing the schedule of reinforcement from MULT EXT, VI 1-min, EXT, VI 1-min to MULT VI 1-min, VI 1-min, VI 1-min, VI 1-min for primary reinforcement birds, and to MULT (Chain VI 1-min, VI 1-min), (CHAIN VI 1-min, VI 1-min for conditioned reinforcement birds. Negative contract was observed for all birds receiving primary reinforcement, but positive induction occurred for two of three birds receiving conditioned reinforcement. In the next phase a response rate decrease was caused by changing the schedule to MULT VI 1-min, VI 1-min, DRO 20-sec, VI 1-min for primary reinforcement birds , and to MULT (CHAIN VI 1-min), VI 1-min, CHAIN DRO 20-sec , VI 1-min) for conditioned reinforcement birds. Two of the primary reinforcement birds showed positive contrast, while the third showed negative induction. Two of the conditioned reinforcement birds showed negative induction, while the third showed no effect. Gradients of stimulus control showed no difference between the groups due to the prolonged training before testing for stimulus control. It was concluded that differential amounts of stimulus control can account for the differences in the schedule interactions in this experiment and those observed in previous research.

This study measures two reinforcement strategies designed to increase repeat donations in first-time volunteer blood donors.

Preference for single versus varied reinforcers was assessed in the context of a token system. This study also assessed the preferences of 4 participants for one stimulus versus a number of qualitatively different stimuli, presented contingent on academic task completion. A paired-choice preference assessment was conducted followed by a reinforcer assessment using a combined reversal and multi-element design. The purpose of these procedures was to determine whether higher rates of responding would occur during conditions in which token reinforcement produced access to back-up reinforcers compared to a no reinforcement condition. Next, the opportunity to choose single versus varied token reinforcers was presented in a concurrent -chains arrangement. The dependent variables were the number of letters traced per min and the number of tokens earned per min during 3-min sessions, and the percentage of selections for single versus varied conditions. Results showed that response rates during the reinforcer assessment were higher during the reinforcement condition relative to the no reinforcement condition. A preference was not detected for 2 of 4 participants when the opportunity to choose from the same or qualitatively different reinforcers was presented. One of 4 participants preferred selecting the varied-choice condition (i.e., qualitatively different back-up reinforcers), and a second participant showed a similar pattern, but results were inconclusive due to limited data.

The prediction of Capaldi's sequential learning theory (i966, 1967, 1970) that resistance to extinction (Rn) increases as a function of the number of successive nonrewarded trials (N-length) conditioned to the instrumental response has recently been supported in a discrete-trials leverpress situation but not in a free-operant leverpress situation (Wolach & Ferraro, 1971). To investigate this discrepancy, 32 male albino rats were trained to leverpress in the presence of a visual sD under one of two N-length conditions (8 or 16) and one of four intertrial interval (ITI) conditions (5, 10, 15, or 30 sec.), the lowest of which corresponded to a freeoperant interresponse time. A subsequent extinction phase revealed that the 16 N-length group displayed greater Rn than the 8 N-length group at each ITI investigated on the dependent measures of extinction speed (p is less than .01) and trials to extinction criterion (p is less than .05). The results were interpreted as supporting the applicability of sequential theory to both discrete-trials and free-operant methodologies.

We evaluated behavior exhibited by individuals with developmental disabilities using progressive ratio schedules. High- and low-preferred stimuli were determined based on the results of a paired-stimulus preference assessment and were evaluated in subsequent reinforcer and progressive ratio assessments using concurrent- and single-operant schedules of presentation in a modified reversal design. Results showed that for two participants, stimuli determined to be low-preferred via a preference assessment functioned as reinforcers when evaluated independently of high-preferred stimuli and under gradually increasing response requirements. The results suggest that for cases in which a high-preferred stimulus is unavailable or unfeasible, the contingent delivery of relatively less-preferred stimuli may maintain appropriate behavior, even as response effort is increased. In addition, results of the progressive ratio evaluation are suggestive of stimulus value.

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A differential reinforcement procedure was investigated as a means for transferring stimulus control from physical guidance to verbal instructions in the training of instruction-following behavior.· An eight year old, severely retarded female was trained to respond to nonsense verbal prompts which, through training, had become discriminative stimuli for (a) "clap your hands", (b) "raise your hand", and (c) "tap the table". The use of differential reinforcement of singular and paired verbal/ physical prompt components increased the response rates to levels above the 80% criterion level. Training of these responses was accomplished across behaviors in a multiple baseline format.

The purpose of this experiment was to evaluate the effects of a conflicting instruction on FR-5 performances by an ABABC design. After all four college students were consistently pressing 1-5-3 followed by sound-clips, the schedule value changed to FR-5 (A). Then they were presented with the written instruction "Press 426" (B) in addition to the previous condition. In the last condition (C), 1-5-3 responses were then scheduled for extinction in three participants and the reinforcer was changed from sound-clips to points for one participant. The results showed that unlike previous experiments, instructions did not override the scheduled contingencies. Instruction-following occurred only when there were no other contingencies (i.e., extinction of 1-5-3) or the scheduled reinforcer for FR-5 performances was weak.