A comparison of presession and within-session reinforcement choice.

Single- and concurrent-operants procedures were used to evaluate the effects of two reinforcement conditions on the free-operant responding of 3 individuals with developmental disabilities and 1 with attention deficit disorder. In the presession choice condition, prior to each session the participant chose one item from an array of three different highly preferred stimuli. This item was delivered by the experimenter on each reinforcer delivery during that session. In the within-session choice condition, each reinforcer delivery consisted of placing an array of three different highly preferred stimuli in front of the participant, who was allowed to select one. Only one of the two reinforcement conditions was in effect for any particular session in single-operant phases. Buttons associated with each reinforcement condition were present, and the participant could allocate responses to one or the other in concurrent-operants phases. Data showed substantially more responding to the button associated with within-session choice than presession choice during concurrent-operants phases. This effect was not as apparent during single-operant phases, suggesting that a concurrent-operants procedure provided the more sensitive evaluation of within-session and presession reinforcer choice effects.     

Effects of varying stimulus disparity and the reinforcer ratio in concurrent-schedule and signal-detection procedures.

The present study measured the effects of stimulus and reinforcer variations on pigeons' behavior in two different choice procedures. Two intensities of white light were presented as the stimuli on the main key in a switching-key concurrent schedule and as the sample stimuli in a signal-detection procedure. Under both procedures, the scheduled rate of reinforcement was varied across conditions to produce various ratios of obtained reinforcement. These ratios were obtained for seven pairs of light intensities. In the concurrent schedules, the effects of reinforcer-ratio variations were positively correlated with the physical disparity between the two light intensities. In the signal-detection procedure, changes in the reinforcer ratio produced greater effects on performance when stimulus disparity was very low or very high compared to those found at intermediate levels of stimulus disparity. This discrepancy creates a dilemma for existing behavioral models of signal-detection performance.     

EFFECTS OF REINFORCEMENT CHOICE ON TASK RESPONDING IN INDIVIDUALS WITH DEVELOPMENTAL DISABILITIES

The effects of reinforcement choice on task performance were examined with 6 individuals who had been diagnosed with severe to profound mental retardation. Five highly preferred items were identified for each participant via stimulus preference assessments. Participants then were exposed to choice and no-choice conditions that were alternated within reversal and multielement designs. During choice sessions, participants were permitted to select between two preferred stimuli contingent on responding. During no-choice sessions, the therapist delivered a single item contingent on responding. Preference for the stimuli was held constant across conditions by yoking the items delivered during no-choice sessions to those selected during the immediately preceding choice sessions. All participants exhibited similar rates of responding across choice and no-choice conditions. These findings indicate that for individuals with severe disabilities, access to choice may not improve task performance when highly preferred items are already incorporated into instructional programs.     

Discrete-trial choice in pigeons: Effects of reinforcer magnitude

The preference of pigeons for large reinforcers which occasionally followed a response versus small reinforcers which invariably followed a response was studied in a discrete-trial situation. Two differently colored keys were associated with the two reinforcement alternatives, and preference was measured as the proportion of choice trials on which the key associated with uncertain reinforcement was pecked. A combination of choice and guidance trials insured that received distributions of reinforcement equalled the scheduled distributions. For five of six subjects, preference for the uncertain reinforcer appeared to be a linear function of the magnitude of the certain reinforcer. In addition, there was greater preference for the response alternative associated with uncertain reinforcement than would be expected on the basis of net reinforcer value.     

Effects of reinforcer delays on choice as a function of income level

Three rats earned their daily food ration by responding during individual trials either on a lever that delivered one food pellet immediately or on a second lever that delivered three pellets after a delay that was continuously adjusted to ensure substantial responding to both alternatives. Choice of the delayed reinforcer increased when the number of trials per session was reduced. This result suggests that models seeking closure on choice effects must include a parameter reflecting how preference changes with sessionwide income. Moreover, models positing that reinforcer probability and immediacy (1/delay) function equivalently in choice are called into question by the finding that probability and immediacy produce opposing effects when income level is changed.     

Effects on choice of reinforcement delay and conditioned reinforcement

Pigeons chose between fixed-interval schedules of different durations presented in the terminal links of concurrent-chains schedules. The pair of schedules was always in the ratio of 2:1, but the absolute duration of the fixed intervals varied. In one set of conditions, the different terminal-link schedules were associated with different keylight stimuli (cued conditions). In a second set of conditions, the different terminal-link schedules were associated with the same stimulus (uncued conditions). Results from the cued conditions replicated previous findings that preference for the shorter fixed-interval schedule increased with fixed-interval duration. Preferences in the uncued conditions were lower than in the corresponding cued conditions but also increased with fixed-interval length. In addition, the degree of control under the uncued conditions was correlated with the extent to which the schedule during the terminal link was discriminated immediately upon entry into the terminal link. The pattern of results in both conditions was inconsistent with the notion that choice behavior matches relative immediacy of reinforcement. Reanalysis of previous evidence for matching (Chung and Herrnstein, 1967) showed that matching in fact did not occur, as the preferences of their subjects for the shorter of two delays also increased with the absolute size of the delays.     

Humans' sensitivity to variation in reinforcer amount: Effects of the method of reinforcer delivery

Two experiments examined human subjects' sensitivity to variation in reinforcer amount under different methods of reinforcer delivery. Subjects chose between schedules varying in terms of amount and/or delay of reinforcement, the reinforcer being points exchangeable for money. In Experiment 1, reinforcer amount was manipulated by varying the monetary value of the points across conditions while the number of seconds of access to a consummatory response remained constant. Choice was strongly sensitive to reinforcer amount and indicative of self-control, as in previous experiments. In Experiment 2, reinforcer amount was manipulated by automatically delivering different numbers of points during the amount period, and the consummatory response was eliminated. Sensitivity to variation in reinforcer amount was significantly lower than in Experiment 1. Furthermore, the subjects in Experiment 2 exhibited significantly less self-control than did the subjects in Experiment 1. Humans' sensitivity to variation in reinforcer amount appears to be affected by factors that enhance the discrimi-nability of the consequences of responding.     

Effects of reinforcement context on choice

Two experiments investigated the effects of successive reinforcement contexts on choice. In the first, concurrent variable-interval schedules of primary reinforcement operated during the initial links of concurrent chains. The rate of this reinforcement arranged by the concurrent schedules was decreased across conditions: When it was higher than the terminal-link rate, preference for the higher frequency initial-link schedule increased relative to baseline. (During baseline, a standard concurrent-schedule procedure was in effect). When the initial-link reinforcement rate was lower than the terminal-link rate, preference converged toward indifference. In the second experiment, a chain schedule was available on a third key while a concurrent schedule was in effect on the side keys. When the terminal link of the chain schedule was produced, the side keys became inoperative. Availability of the chain schedule did not affect choice between the concurrent schedules. These results show that only when successive reinforcement contexts are produced by choice responding do those successive contexts affect choice in concurrent schedules.     

Discriminative functions of schedule stimuli and memory: a combination of schedule and choice procedures

Pigeons responded under a combination brief-stimulus schedule and choice procedure. Normally, a fixed-interval schedule was in effect, where completion randomly produced either a brief stimulus or food. Intermittently, this schedule was interrupted by a choice arrangement. Two choice keys were lit, either a short or a long time since a prior event (food or stimulus). One choice response produced food if the time had been short, and the alternate response produced food if the time had been long. Across conditions, the duration of the fixed-interval schedule was varied, the stimuli that comprised the brief-stimulus operation were changed, and the stimuli were presented as paired and nonpaired with food. The focus of the study was the control of both schedule performance and choice responding across conditions. The results showed that choice accuracy was correlated with the degree of fixed-interval curvature, the response pattern of a pause followed by a gradually accelerated rate. As fixed-interval schedule duration was increased, both the degree of fixed-interval curvature and choice accuracy decreased. The particular brief stimulus used affected schedule and choice performance, with a more salient stimulus producing a greater degree of curvature and higher accuracy. Pairing and nonpairing operations produced striking differences in performance with the less salient brief stimulus, but not with the more salient stimulus. The results suggest that brief-stimulus schedule performance may be conceptualized in the context of memory research.     

Evaluation of a vocal mand assessment and vocal mand training procedures

A common deficiency in the verbal repertoires of individuals with autism and related disorders is the absence of socially appropriate vocal mands. The vocal mand repertoires of these individuals may be lacking in several respects: (a) The individual might engage in no mands whatsoever, (b) the mand might be topographically dissimilar to an appropriate response, (c) the mand might be only partially topographically similar to an appropriate response, and (d) the mand might occur only after prompting. Depending on specific deficiencies in an individual's repertoire, different procedures for establishing appropriate mands may be needed. The purpose of Study 1 was to evaluate an assessment prior to teaching vocal mands for 3 individuals with developmental disabilities. The assessment showed that 1 individual displayed partial utterances of mands, 1 displayed vocal mands after mands had been reinforced, and 1 displayed vocal mands when prompted. Thus, in Study 2, a different teaching strategy was tested for each individual. Results showed that the assessment information could be linked directly to mand training for all 3 participants.     

Effects of response type on pigeons' sensitivity to variation in reinforcer amount and reinforcer delay

Twelve pigeons, divided into two groups, responded on concurrent nonindependent variable-interval schedules to obtain access to grain by either pecking keys or pressing treadles. Either the amount of grain or the delay to the receipt of grain was varied in separate conditions to determine the sensitivity of relative responding to variation in reinforcer amount (s_A), the sensitivity to variation in reinforcer delay (s_D), and s_A/s_D, a measure related to self-control. There were no significant differences between the two groups in the values of s_A, s_D, and s_A/s_D. These results suggest that the values of s_A, s_D, and s_A/s_D for pigeons may be similar across these two types of responses.     

Delay and number of food reinforcers: Effects on choice and latencies

Pigeons were given a choice between two identical-duration situations (terminal links of chain schedules). One terminal link of the choice pair provided two food deliveries, and the other provided five. The exact times of these food deliveries differed between the terminal links and were varied over conditions. A single response during the initial link gave immediate access to the corresponding terminal link. Forced trials, during which only one of the initial-link keys was lighted, were interspersed with choice trials during which both initial-link keys were lighted. Choice tended to favor whichever terminal link was correlated with the higher sum of the immediacies (i.e., the sum of the reciprocals of the delays to each of the reinforcers following the choice, with all delays measured from the choice). Latencies on forced trials and on choice trials also were related (negatively) to the sum of the immediacies. This correlation among response measures (choice and latencies) suggests that both measures are manifestations of the effect of conditioned reinforcement on response tendencies.     

EVALUATION OF CLIENT PREFERENCE FOR FUNCTION-BASED TREATMENT PACKAGES

Functional communication training (FCT) and noncontingent reinforcement (NCR) are commonly prescribed treatments that are based on the results of a functional analysis. Both treatments involve delivery of the reinforcer that is responsible for the maintenance of destructive behavior. One major difference between the two treatment procedures is that client responding determines reinforcement delivery with FCT (e.g., reinforcement of communication is delivered on a fixed-ratio 1 schedule) but not with NCR (e.g., reinforcement is delivered on a fixed-time 30-s schedule). In the current investigation, FCT and NCR were equally effective in reducing 2 participants' destructive behavior that was sensitive to attention as reinforcement. After the treatment analysis, the participants' relative preference for each treatment was evaluated using a modified concurrent-chains procedure. Both participants demonstrated a preference for the FCT procedure. The results are discussed in terms of treatment efficacy and preference for control over when reinforcement is delivered. In addition, a method is demonstrated in which clients with developmental disabilities can participate in selecting treatments that are designed to reduce their destructive behavior.     

ON THE RELATIVE REINFORCING EFFECTS OF CHOICE AND DIFFERENTIAL CONSEQUENCES

Research on the reinforcing effects of providing choice-making opportunities to individuals with developmental disabilities (i.e., allowing them to choose reinforcers or tasks) has produced inconsistent results, perhaps because the mechanisms underlying such effects remain unclear. Choice may produce a reinforcement effect because it is correlated with differential consequences (i.e., choice may increase one's access to higher preference stimuli), or it may have reinforcement value independent of (or in addition to) the chosen stimulus. In Experiment 1, we used a concurrent-operants arrangement to assess preference for a choice condition (in which participants selected one of two available reinforcers) relative to a no-choice condition (in which the therapist selected the same reinforcers on a yoked schedule). All 3 participants preferred the choice option. In Experiment 2, we altered the schedules so that the participant selected one of two lower preference reinforcers in the choice condition, whereas the therapist selected a higher preference stimulus for the participant either half or all of the time in the no-choice condition. Participants typically allowed the therapist to select reinforcers for them (i.e., they allocated responding to the no-choice condition) when it resulted in greater access to higher preference stimuli.     

An evaluation of simultaneous and sequential presentation of preferred and nonpreferred food to treat food selectivity

In the current investigation, we compared two methods of food presentation (simultaneous vs. sequential) to increase consumption of nonpreferred food for 3 children with food selectivity. In the simultaneous condition, preferred foods were presented at the same time as nonpreferred food (e.g., a piece of broccoli was presented on a chip). In the sequential condition, acceptance of the nonpreferred food resulted in presentation of the preferred food. Increases in consumption occurred immediately during the simultaneous condition for 2 of the 3 participants. For 1 participant, increases in consumption occurred in the simultaneous condition relative to the sequential condition, but only after physical guidance and re-presentation were added to treatment. Finally, consumption increased for 1 participant in the sequential condition, but only after several sessions. These results are discussed in terms of possible mechanisms that may alter preferences for food (i.e., establishing operations, flavor-flavor conditioning).     

The effects of noncontingent delivery of high- and low-preference stimuli on attention-maintained destructive behavior

An adolescent with severe mental retardation and cerebral palsy who displayed attention-maintained destructive behavior was exposed to noncontingent reinforcer delivery (NCR) with either a high-preference or a low-preference stimulus while reinforcement for destructive behavior with attention remained in effect (i.e., NCR without extinction). NCR without extinction was effective only when the high-preference stimulus was available, suggesting that systematic assessment of stimulus quality may enhance the effectiveness of NCR with alternative stimuli.     

Percentage reinforcement and choice

Pigeons responded on identical concurrent variable-interval schedules (choice phase), producing outcomes of either periodic reinforcement schedules always terminating in reinforcement (reliable schedule) or otherwise identical schedules providing reinforcement on only a percentage of instances (percentage reinforcement schedule). Comparisons of this type constituted two assessments of the generality of preference for percentage reinforcement reported by Kendall (1974). In a third set of conditions, a reliable schedule was pitted against a percentage reinforcement schedule in which the more negative outcome was a leaner schedule of reinforcement (rather than nonreinforcement, as in the other two conditions). In all three types of conditions, the schedule providing the higher rate of reinforcement was preferred. Results from a subsequent manipulation suggest that Kendall's contrasting results may have depended on the fact that the stimuli in his choice phase (unlit keys) were physically identical to the stimulus correlated with the nonchosen outcome in his outcome phase.