Microcomputer-based programmed instruction in identity matching to sample for persons with severe disabilities

Three individuals with mental retardation, who had failed to learn identity matching to sample with standard fading and prompting procedures, were given microcomputer-based programmed instruction. The methods were based on an analysis of two features of typical identity matching procedures: (a) within each trial, the current sample stimulus must control comparison selection, and (b) across trials, specific comparison stimuli must function both as S+ and as S–, depending upon the sample presented (conditional discrimination). During the first phase of training, one-trial acquisition of discriminative stimulus control was established in a nonconditional discrimination context where the S+ or S– functions of specific stimuli did not change from trial to trial. After one-trial learning was established, conditional discrimination was programmed by gradually introducing reversals of S+/S– stimulus functions. All three participants learned to perform conditional identity matching. Avenues for further analysis of the prerequisites for conditional discrimination and continued development of programmed methods are discussed.     

Irrelevance of sample stimuli and directed forgetting in pigeons

A successive matching procedure was used to investigate which aspect of the test-omission procedure is responsible for establishing a postsample stimulus as a cue to forget in pigeons. It was found that a postsample stimulus that reliably followed a sample that was irrelevant to performance functioned as a cue to forget. This result was obtained regardless of whether termination of that postsample stimulus was followed by reinforcement or by the presentation of sample-independent discriminative stimuli. It was also found that a postsample stimulus that functioned as a cue to forget at the beginning of training lost that function when it was repeatedly presented on trials in which the sample was relevant to performance. These findings reveal that (a) neither a reduction in reinforcement rate nor the omission of the opportunity for discriminated responding is necessary to establish an effective cue to forget and (b) irrelevance of the sample to performance is a sufficient condition to establish a cue to forget. These results suggest that a postsample stimulus that is presented on trials in which remembering the sample is not reinforced differentially will come to set the occasion for not remembering the sample.     

THE LOCAL ORGANIZATION OF BEHAVIOR: DISCRIMINATION OF AND MEMORY FOR SIMPLE BEHAVIORAL PATTERNS

A procedure was developed to enable nonverbal organisms to report what they remember of the temporal organization of their recent behavior. A baseline behavior with known temporal structure was established by a concurrent variable-interval variable-interval schedule for two temporal patterns of behavior (two different classes of reinforced interresponse times). The five pigeon subjects emitted these two temporal patterns on a center key and were occasionally given a short-term memory probe for their most-recently-emitted pattern. The probes consisted of symbolic delayed matching-to-sample tests, in which a response on a green side key was reinforced if the most recent pattern belonged to the shorter reinforced class, and a response to a red side key was reinforced if the most recent pattern belonged to the longer reinforced class. All subjects could report with over ninety percent accuracy what their most recently emitted behavioral pattern was when a retention interval separating the pattern from the memory probe was only .1 seconds. The retention interval was then manipulated, and it was found that recall for a pattern was frequently above chance after a delay of as much as eight seconds. Thus, pigeons can remember their most recent interresponse time not only right after it is emitted, but for several seconds thereafter. In other conditions, the patterns themselves were manipulated. It was found that as the patterns became more similar, discrimination became poorer. These results agree with the view that reinforcement tends to organize and integrate the local structure of behavior to the extent to which that structure is remembered.     

Negative reinforcement with shock-frequency increase

Two avoidance-conditioning experiments in which responding delayed shocks are reported. Rats receiving an average of two shocks per minute (imposed condition) could produce, by pressing a bar, a 3-min alternate condition. Six (Experiment I) or more (Experiment II) shocks occurred in the alternate condition. All shocks in the alternate condition were delayed and delivered at 1-sec intervals. With long delays, all subjects produced the alternate condition and spent a large percentage of each session in the alternate condition. The first experiment demonstrated that the longer the delay from onset of the alternate condition to onset of the shocks, the more session time spent in the alternate condition. The second experiment indicated that despite increased shock frequency, behavior is acquired and maintained when responding leads to sufficient delay. Individual subjects produced the alternate condition by bar pressing in essentially one of two patterns. One pattern, termed postshock, involved bar pressing immediately after shock; the other, termed posttransition, involved responding immediately after the transition from the alternate to the imposed condition. These results indicate that shock-frequency reduction is not necessary for avoidance conditioning; delay to shock onset is sufficient.     

Integrated delays to shock as negative reinforcement

Rats were shocked at the rate of two per minute until they pressed a lever. In Experiment I, shocks were delivered at variable-time intervals averaging 30 sec; in Experiment II, shocks were delivered at fixed-time intervals of 30 sec. A response produced an alternate condition for a fixed-time period. The shock frequency following a response, calculated over the whole alternate condition, was two per minute. The pattern of shocks in the alternate condition was controlled so that the first shock occurred at the same time as it would have occurred had the response not been emitted; the remaining shocks were delayed until near the end of the alternate condition. Bar pressing was acquired in both experiments. This finding is not explained by two-factor theories of avoidance and is inconsistent with the notion that overall shock-frequency reduction is necessary for negative reinforcement. The data imply that responding is determined by the integrated delays to each shock following a response versus the integrated delays to shock in the absence of a response.     

Determination of discount functions in rats with an adjusting-amount procedure.

An adjusting-amount procedure was used to measure discounting of reinforcer value by delay. Eight rats chose between a varying amount of immediate water and a fixed amount of water given after a delay. The amount of immediate water was systematically adjusted as a function of the rats' previous choices. This procedure was used to determine the indifference point at which each rat chose the immediate amount and the delayed amount with equal frequency. The amount of immediate water at this indifference point was used to estimate the value of the delayed amount of water. In Experiment 1, the effects of daily changes in the delay to the fixed reinforcer (100 microliters of water delivered after 0, 2, 4, 8, or 16 s) were tested. Under these conditions, the rats reached indifference points within the first 30 trials of each 60-trial session. In Experiment 2, the effects of water deprivation level on discounting of value by delay were assessed. Altering water deprivation level affected the speed of responding but did not affect delay discounting. In Experiment 3, the effects of varying the magnitude of the delayed water (100, 150, and 200 microliters) were tested. There was some tendency for the discounting function to be steeper for larger than for smaller reinforcers, although this difference did not reach statistical significance. In all three experiments, the obtained discount functions were well described by a hyperbolic function. These experiments demonstrate that the adjusting-amount procedure provides a useful tool for measuring the discounting of reinforcer value by delay.     

A COMPARISON OF SIMULTANEOUS AND DELAYED REINFORCEMENT AS TREATMENTS FOR FOOD SELECTIVITY

This study compared the relative efficacy of providing simultaneous or delayed reinforcement on food acceptance during meals. The participant was a 7-year-old boy with pervasive developmental disorder and a history of food selectivity. Results indicated that both procedures were effective in increasing acceptance; however, the simultaneous reinforcement procedure produced more rapid behavior change and a higher overall percentage of food acceptance.     

Contingencies promote delay tolerance

The effectiveness of functional communication training as treatment for problem behavior depends on the extent to which treatment can be extended to typical environments that include unavoidable and unpredictable reinforcement delays. Time‐based progressive delay (TBPD) often results in the loss of acquired communication responses and the resurgence of problem behavior, whereas contingency‐based progressive delay (CBPD) appears to be effective for increasing tolerance for delayed reinforcement. No direct comparison of TBPD and CBPD has, however, been conducted. We used single‐subject designs to compare the relative efficacy of TBPD and CBPD. Four individuals who engaged in problem behavior (e.g., aggression, vocal and motor disruptions, self‐injury) participated. Results were consistent across all participants, and showed lower rates of problem behavior and collateral responses during CBPD than during TBPD. The generality of CBPD treatment effects, including optimal rates of communication and compliance with demands, was demonstrated across a small but heterogeneous group of participants, reinforcement contingencies, and contexts.     

Seasonal variation in pigeon body weight and delayed matching-to-sample performance

The weights of 5 pigeons with free access to food, monitored over 3 calendar years in the laboratory, were found to fluctuate with season. All pigeons were at their heaviest in the winter and were lightest in the summer. Five different pigeons performed a standard delayed matching-to-sample task for 44 weeks from January to November. Their weights were held at 85% of their summer free-feeding weights, making their predicted deprivation level higher in the winter relative to predicted winter free-feeding weights. Slopes of forgetting functions fit to weekly response totals for each pigeon were shallower in winter, showing an improvement in accuracy with longer delays. Thus, delayed matching-to-sample performance may have been affected by the practice of maintaining the pigeons at a constant body weight throughout the calendar year.     

The effects of differential training procedures on linked perceptual class formation

When the stimuli in one perceptual class (A') become related to the stimuli in another perceptual class (B'), the two are functioning as a single linked perceptual class. A common linked perceptual class would be the sounds of a person's voice (class A') and the pictures of that person (class B'). Such classes are ubiquitous in real world settings. We describe the effects of a variety of training procedures on the formation of these classes. The results could account for the development of naturally occurring linked perceptual classes. Two perceptual classes (A' and B') were formed in Experiment 1. The endpoints of the A' class were called anchor (Aa) and boundary (Ab) stimuli. Likewise, the anchor and boundary stimuli in the B' class were represented as Ba and Bb. In Experiment 2, the A' and B' classes were linked by the establishment of one of four cross-class conditional discriminations: Aa-->Ba, Aa-->Bb, Ab-->Ba, or Ab-->Bb. Results were greatest after Aa-->Bb training, intermediate after Aa-->Ba and Ab-->Ba training, and lowest after Ab-->Bb training. Class formation was influenced by the interaction of the anchor/boundary values and the sample/comparison functions of the stimuli used in training. Experiment 3 determined whether class formation was influenced by different sets of two cross-class conditional discriminations: Aa-->Ba and Ab-->Bb, or Aa-->Bb and Ab-->Ba. Both conditions produced equivalent results. Similarities were attributable to the use of anchor stimuli as samples and boundary stimuli as comparisons in each training condition. Finally, the results afterjoint Aa-->Ba and Ab-->Bb training were much greater than those produced by summing the results of Aa-->Ba training alone and Ab-->Bb training alone. This same synergy was not observed after joint Aa-->Bb and Ab-->Ba training or either alone.