The independent effects of two signals implemented during treatment with noncontingent reinforcement (NCR) were examined. First, functional analyses showed that problem behavior exhibited by two individuals with developmental disabilities was sensitive to social positive reinforcement. A reversal design was then used to compare the effectiveness of a timer (NCR-visual) to a vocal statement (NCR-vocal) indicating when the stimulus would be returned in the context of a NCR procedure. Results showed that NCR reduced problem behavior for both participants. In addition, for one participant, the NCR-visual condition reduced problem behavior to a greater degree than the NCR-vocal condition. Copyright © 2009 John Wiley & Sons, Ltd.

Environmental operations may be classified according to whether they have evocative or function-altering effects. Evocative events, such as the presentation of unconditioned and conditioned stimuli, establishing operations, and discriminative stimuli, serve to increase, decrease, or maintain the momentary frequency of behavior. Function-altering operations, such as operant and respondent conditioning, the correlation of stimuli, and the presentation of certain verbal stimuli, serve to increase, decrease, or maintain the evocative and function-altering (e.g., reinforcing or punishing) functions of other events. This paper expands upon the functional taxonomy of environmental events described by Michael (1993a). The resulting classification scheme should permit behavior analysts to more easily respond to similarities and differences between functional environmental events. This paper discusses implications of the suggested taxonomy for how behavior analysts talk about motivational variables, discriminative stimuli, the operant unit of analysis, and the distinction between operant and respondent conditioning.

The present experiment examined the effects of different delays of food delivery with and without a response-produced auditory stimulus on the acquisition of a spatially defined operant in rats. The operant was breaking a photoelectric beam located near the ceiling at the rear of the experimental chamber. In five groups of experimentally naive rats, the effects on photobeam-break responses of two different reinforcement delays (4 s and 10 s) with and without a response-produced auditory stimulus were compared during eight 1-hr sessions. In one control group (0-s delay), an immediate (i.e., 0.25-s) reinforcement contingency was in effect and in another control group (no food), responses were measured in the absence of any reinforcement contingencies. Results showed that rates of acquisition and responding were higher with shorter reinforcement delays and when there was a response-produced auditory stimulus. These results extend previous findings showing that neither direct shaping nor immediate reinforcement is necessary for operant conditioning. However, the present results demonstrate that the speed and extent of conditioning depends on the temporal relation between the response and the reinforcer. The findings are discussed in terms of a conditioned reinforcement analysis of the stimuli produced by operant responses.

The effects of acute administrations of d-amphetamine (0.56, 1.0, 1.78, 3.2, and 5.6 mg/kg), methaqualone (5.6, 10, 18, 32, and 56 mg/kg), and phencyclidine (0.3, 0.56, 1.0, and 1.78 mg/kg) on the reaction time of pigeons were examined. In the reaction time assay, birds were trained to depress and hold a foot treadle until a stimulus change occurred. Releases within 2 s of the stimulus change were reinforced with food; premature releases or releases occurring after the 2-s limited hold were not reinforced. At relatively high doses, each of the drugs decreased the percentage of responses that were reinforced. Methaqualone and phencyclidine usually increased median reaction times at these doses, whereas the effects of d-amphetamine on reaction time were less clear.

The differential outcomes effect refers specifically to the increase in speed of acquisition or terminal accuracy that occurs in discrimination training when each of two or more discriminative stimuli is correlated with a particular outcome (e.g., type of reinforcer). The present review summarizes studies concerned with the differential outcomes effect, provides a behavioral analysis of the phenomenon in terms of operant-respondent interactions, and offers suggestions for future research.

Pigeons were exposed to delayed-matching-to-sample (DMTS) procedures in which food or a flash of the feeder light followed correct responses. When these consequences were correlated with a particular stimulus (e.g., food followed matching responses to red and a flash of the feeder light followed matching responses to green), accuracy was higher (i.e., stimulus control was greater) than when discriminative stimuli and consequences were not correlated. Although stimulus control in the absence of drug appeared to be weaker under the uncorrelated procedure, neither d-amphetamine (0.5-3.0 mg/kg) in Experiment 1 nor ethosuximide (40-160 mg/kg) in Experiment 2 disrupted accuracy to a greater extent under that procedure. These results, like those of a prior investigation, suggest that drug effects are similar under DMTS procedures regardless of whether correlated or uncorrelated outcomes are arranged.

The present study examined the acquisition of lever pressing in rats under three procedures in which food delivery was delayed by 4, 8, and 16 seconds relative to the response. Under the nonresetting delay procedure, food followed the response selected for reinforcement after a specified interval elapsed; responses during this interval had no programmed effect. Under the resetting procedure, the response selected for reinforcement initiated an interval to food delivery that was reset by each subsequent response. Under the stacked delay procedure, every response programmed delivery of food t seconds after its occurrence. Two control groups were studied, one that received food immediately after each lever press and another that never received food. With the exception of the group that did not receive food, responding was established with every procedure at every delay value without autoshaping or shaping. Although responding was established under the resetting delay procedure, response rates were generally not as high as under the other two procedures. These findings support the results of other recent investigations in demonstrating that a response not previously reinforced can be brought to strength by delayed reinforcement in the absence of explicit training.

Four pigeons were given a choice between two sequences of fixed-ratio schedules. The second fixed ratio was a fixed-ratio 5 followed by 2-s access to grain in one sequence and a fixed-ratio 45 followed by 8-s access to grain in the alternative. In Phase 1, the initial fixed-ratio schedules of each sequence, which were always equal, varied from fixed-ratio 1 to fixed-ratio 50. At each initial fixed-ratio value, 3-s access to grain and a 0.25-s hopper flash were programmed. When the initial fixed ratio was small, the sequence with the 2-s reinforcer was preferred. Preference switched to the sequence with the 8-s reinforcer when the initial fixed ratio increased. In Phase 2, the effects of a 3-s hopper flash were compared with those of a 0.25-s hopper flash. The results showed that preference for the sequence with the 8-s reinforcer increased with hopper-flash duration. Together, Phase 1 and Phase 2 results show that reinforcer magnitude and ratio size of the second fixed ratio can affect choice, but their relative effects depend on initial fixed-ratio size and reinforcer duration.

Many definitions of reinforcer and discriminative stimulus found in behavioral texts include a requirement of temporal proximity between stimulus and response. However, this requirement is not consistently adopted. We present additional evidence from a questionnaire that was sent to members of the editorial boards of several behavioral journals showing that there is not universal agreement concerning the temporal parameters accepted in the definitions of reinforcer and discriminative stimulus. We suggest that the disagreement over the definitions of these essential terms ought to be at least addressed if not resolved. Because the discrepancy usually occurs when the behavior of verbal humans is at issue, we urge behavior analysts to be conservative when extending the terms reinforcer and discriminative stimulus from the behavior of nonhumans in the laboratory to human behavior where the effects of many stimuli may depend in part on sophisticated verbal repertoires.

Pigeons pecked a key under two-component multiple variable-ratio schedules that offered 8-s or 2-s access to grain. Postreinforcement pausing and the rates of responding following the pause (run rates) in each component were measured as a function of variable-ratio size and the size of the lowest ratio in the configuration of ratios comprising each schedule. In one group of subjects, variable-ratio size was varied while the size of the lowest ratio was held constant. In a second group, the size of the lowest ratio was varied while variable-ratio size was held constant. For all subjects, the mean duration of postreinforcement pausing increased in the 2-s component but not in the 8-s component. Postreinforcement pauses increased with increases in variable-ratio size (Group 1) and with increases in the lowest ratio (Group 2). In both groups, run rates were slightly higher in the 8-s component than in the 2-s component. Run rates decreased slightly as variable-ratio size increased, but were unaffected by increases in the size of the lowest ratio. These results suggest that variable-ratio size, the size of the lowest ratio, and reinforcer magnitude interact to determine the duration of postreinforcement pauses.