Stimulus Equivalence: Effects Of A Default-response Option On Emergence Of Untrained Stimulus Relations

Human subjects were exposed to a concurrent-chains schedule in which reinforcer amounts, delays, or both were varied in the terminal links, and consummatory responses were required to receive points that were later exchangeable for money. Two independent variable-interval 30-s schedules were in effect during the initial links, and delay periods were defined by fixed-time schedules. In Experiment 1, subjects were exposed to three different pairs of reinforcer amounts and delays, and sensitivity to reinforcer amount and delay was determined based on the generalized matching law. The relative responding (choice) of most subjects was more sensitive to reinforcer amount than to reinforcer delay. In Experiment 2, subjects chose between immediate smaller reinforcers and delayed larger reinforcers in five conditions with and without timeout periods that followed a shorter delay, in which reinforcer amounts and delays were combined to make different predictions based on local reinforcement density (i.e., points per delay) or overall reinforcement density (i.e., points per total time). In most conditions, subjects' choices were qualitatively in accord with the predictions from the overall reinforcement density calculated by the ratio of reinforcer amount and total time. Therefore, the overall reinforcement density appears to influence the preference of humans in the present self-control choice situation.     

Choice with delayed and probabilistic reinforcers: effects of prereinforcer and postreinforcer stimuli.

In Experiment 1, pigeons' pecks on a green key led to a 5-s delay with green houselights, and then food was delivered on 20% (or, in other conditions, 50%) of the trials. Pecks on a red key led to an adjusting delay with red houselights, and then food was delivered on every trial. The adjusting delay was used to estimate indifference points: delays at which the two alternatives were chosen about equally often. Varying the presence or absence of green houselights during the delays that preceded possible food deliveries had large effects on choice. In contrast, varying the presence of the green or red houselights in the intertrial intervals had no effects on choice. In Experiment 2, pecks on the green key led to delays of either 5 s or 30 s with green houselights, and then food was delivered on 20% of the trials. Varying the duration of the green houselights on nonreinforced trials had no effect on choice. The results suggest that the green houselights served as a conditioned reinforcer at some times but not at others, depending on whether or not there was a possibility that a primary reinforcer might be delivered. Given this interpretation of what constitutes a conditioned reinforcer, most of the results were consistent with the view that the strength of a conditioned reinforcer is inversely related to its duration.     

DOES USE OF TANGIBLE REWARDS WITH INDIVIDUAL CHILDREN AFFECT PEER OBSERVERS?1

The common assumption that employing tangible rewards with individual children will have adverse effects upon peer observers was studied in the preschool setting. Multiple-subject, multiple-baseline procedures were applied to two classes of children, aged 3.5 to 6 yr. In each group, three consecutive children with low base rates of in-seat behavior received a verbal contingency and food rewards for sitting, while peers (with either low or high rates of in-seat behavior) received neither food nor teacher attention for sitting. Peer reactions measured were in-seat behavior, aggression, nonaggressive disruptive behavior, and complaints. The procedures neither decreased the in-seat behavior of peer observers, nor increased their aggressive or disruptive behavior. On the contrary, peers with low base rates of sitting initially displayed an abrupt, but temporary, increase in sitting. Moreover, although no compensatory attention was delivered, all children exhibited improved sitting by the end of the study. Complaints, which consisted mainly of requests for rewards, decreased in frequency with successive program phases, and within each phase. It is suggested that the class improvement in sitting behavior and the absence of negative effects on observers may be partially due to the high frequency of attention the teacher maintained for other desired behavior and the lack of attention to children's complaints.     

Concurrent second-order schedules of reinforcement

Responses on one key (the main key) of a two-key chamber produced food according to a second-order variable-interval schedule with fixed-interval schedule components. A response on a second key (the changeover key) alternated colors on the main key and provided a second independent second-order variable-interval schedule with fixed-interval components. The fixed-interval component on one variable-interval schedule was held constant at 8 sec, while the fixed interval on the other variable-interval schedule was varied from 0 to 32 sec. Under some conditions, a brief stimulus terminated each fixed interval and generated fixed-interval patterns; in other conditions, the brief stimulus was omitted. Relative response rate and relative time deviated substantially from scheduled relative reinforcement rate and, to a lesser extent, from obtained relative reinforcement rate under both brief-stimulus and no-stimulus conditions. Matching was observed with equal components on both schedules; with unequal components, increasingly greater proportions of time and responses than the matching relation would predict were spent on the variable-interval schedule containing the shorter component. Preference for the shorter fixed interval was typically more extreme under brief-stimulus than under no-stimulus schedules. The results limit the extension of the matching relation typically observed under simple concurrent variable-interval schedules to concurrent second-order variable-interval schedules.     

Control by reinforcers across time and space: A review of recent choice research

Reinforcers affect behavior. A fundamental assumption has been that reinforcers strengthen the behavior they follow, and that this strengthening may be context‐specific (stimulus control). Less frequently discussed, but just as evident, is the observation that reinforcers have discriminative properties that also guide behavior. We review findings from recent research that approaches choice using nontraditional procedures, with a particular focus on how choice is affected by reinforcers, by time since reinforcers, and by recent sequences of reinforcers. We also discuss how conclusions about these results are impacted by the choice of measurement level and display. Clearly, reinforcers as traditionally considered are conditionally phylogenetically important to animals. However, their effects on behavior may be solely discriminative, and contingent reinforcers may not strengthen behavior. Rather, phylogenetically important stimuli constitute a part of a correlated compound stimulus context consisting of stimuli arising from the organism, from behavior, and from physiologically detected environmental stimuli. Thus, the three‐term contingency may be seen, along with organismic state, as a correlation of stimuli. We suggest that organisms may be seen as natural stimulus‐correlation detectors so that behavioral change affects the overall correlation and directs the organism toward currently appetitive goals and away from potential aversive goals. As a general conclusion, both historical and recent choice research supports the idea that stimulus control, not reinforcer control, may be fundamental.     

The absence of numbers to express the amount may affect delay discounting with humans

Human delay discounting is usually studied with experimental protocols that use symbols to express delay and amount. In order to further understand discounting, we evaluated whether the absence of numbers to represent reward amounts affects discount rate in general, and whether the magnitude effect is generalized to nonsymbolic situations in particular. In Experiment 1, human participants were exposed to a delay‐discounting task in which rewards were presented using dots to represent monetary rewards (nonsymbolic); under this condition the magnitude effect did not occur. Nevertheless, the magnitude effect was observed when equivalent reward amounts were presented using numbers (symbolic). Moreover, in estimation tasks, magnitude increments produced underestimation of large amounts. In Experiment 2, participants were exposed only to the nonsymbolic discounting task and were required to estimate reward amounts in each trial. Consistent with Experiment 1, the absence of numbers representing reward amounts produced similar discount rates of small and large rewards. These results suggest that value of nonsymbolic rewards is a nonlinear function of amount and that value attribution depends on perceived difference between the immediate and the delayed nonsymbolic rewards.     

Effects of negative incentive shifts in food reward on rats' consumption of concurrent ethanol solutions

Frustration stress, typically operationalized as the unexpected loss of reinforcement, has been shown to engender substance use. Abrupt reductions in reinforcer magnitude likely also function as frustration stressors. These negative incentive shifts were previously shown to produce tap‐ and sweetened‐water drinking in rats. The purpose of this study was to investigate whether these shifts in food reward would occasion oral ethanol self‐administration. Nine male Long‐Evans rats operated on a two‐component multiple fixed‐ratio schedule with signaled components producing either a large (4 pellets) or small (1pellet) reinforcer. Components were pseudorandomly arranged to present 4 transitions between past and upcoming reinforcer magnitudes: small‐to‐large, small‐to‐small, large‐to‐large, and large‐to‐small (negative incentive shift). Experiment 1 investigated the effects of negative incentive shifts on consumption of concurrent, freely available 10% sucrose, 10% sucrose plus 10% ethanol, and following sucrose fading, 10% ethanol. Experiment 2 entailed continuation of schedule contingencies with a dose manipulation of 4 ethanol concentrations (0, 5, 10, and 20%) to assess dose‐dependent differences in transition‐type control and consumption. A lever‐press extinction condition was then conducted with 10% ethanol availability. In this novel model of frustration stress, negative incentive shifts prompted ethanol self‐administration at each dose investigated, whereas the other transitions did not.     

Assessing preferences of individuals with developmental disabilities using alternative stimulus modalities: A systematic review

The purpose of this systematic review was to identify investigations comparing the efficacy of alternative modality (e.g., pictorial, verbal, video) stimulus preference assessments for individuals with developmental disabilities. We identified articles by searching peer‐reviewed journals using the PsycINFO and ERIC databases, conducting table of contents searches of common behavioral outlets, and conducting ancestral searches of recent reviews and practitioner summaries of preference assessment methodology. A total of 32 articles met our inclusion criteria. These studies were then coded across a variety of features to gain a better understanding of the efficacy of alternative format preference assessments for individuals with developmental disabilities. In addition, we reviewed this literature for the use of prerequisite‐skill assessments and contingent‐reinforcer access to further investigate the relation between these variables and the accuracy of pictorial, verbal, and video preference assessments. A variety of methodological concerns are discussed as well as suggestions for future research.     

Assessing the generality and durability of interview‐informed functional analyses and treatment

Due to the limited research demonstrating socially valid outcomes of function‐based treatments in ecologically relevant environments (Santiago, Hanley, Moore, & Jin, 2016), we replicated and extended the effects of the interview‐informed functional analysis and skill‐based treatment procedure described by Hanley, Jin, Vanselow, and Hanratty (2014) with two children diagnosed with autism in a home setting. The assessment and treatment was implemented by a home‐based service provider and treatment was extended to the participants’ parents. Following the interview‐informed functional analyses, we taught the participants functional communication responses and to engage in less‐preferred activities when functional communication outcomes were delayed. We observed large reductions in problem behavior following the introduction of the function‐based treatment. The effects extended to novel settings, stimuli, and caregivers and the results maintained at 6‐week follow‐ups.     

Using stimulus preference assessments to identify preferred break environments

A pictorial preference assessment was conducted for 2 individuals with autism who had programmed breaks in their behavior plans. Assessed break environments were individualized, based on indirect assessments and direct observations. The most highly (HP) and least preferred (LP) environments and a control with no associated break were included in a subsequent reinforcer assessment using a concurrent‐chains arrangement within a reversal design. Participants selected a multitask sequence (initial link) associated with one of the break environments. Phase A evaluated the reinforcing properties of all three breaks; the HP was removed in Phase B. Both participants allocated more responding to HP than LP, and to LP than control, suggesting that breaks functioned as reinforcers. The results indicated that preference assessment technology can be used to identify highly preferred breaks that function as reinforcers. Social validity measures indicated that the individuals' clinicians found the results useful for future clinical programming.