We assessed the efficacy of, and preference for, accumulated access to reinforcers, which allows uninterrupted engagement with the reinforcers but imposes an inherent delay required to first complete the task. Experiment 1 compared rates of task completion in 4 individuals who had been diagnosed with intellectual disabilities when reinforcement was distributed (i.e., 30-s access to the reinforcer delivered immediately after each response) and accumulated (i.e., 5-min access to the reinforcer after completion of multiple consecutive responses). Accumulated reinforcement produced response rates that equaled or exceeded rates during distributed reinforcement for 3 participants. Experiment 2 used a concurrent-chains schedule to examine preferences for each arrangement. All participants preferred delayed, accumulated access when the reinforcer was an activity. Three participants also preferred accumulated access to edible reinforcers. The collective results suggest that, despite the inherent delay, accumulated reinforcement is just as effective and is often preferred by learners over distributed reinforcement.

Competing stimulus assessments (CSAs) are designed to identify stimuli that, when made freely available, reduce problem behavior. Although CSAs have demonstrated utility, identifying competing stimuli can be difficult for some individuals. The current study describes outcomes from an augmented CSA (A-CSA) for 6 consecutively encountered cases with treatment-resistant subtypes of automatically maintained problem behavior. When test stimuli were made freely available, only between 0 and 1 effective competing stimuli were identified for each case. Prompting and response blocking were temporarily employed in succession to promote engagement with stimuli and disrupt problem behavior. When those procedures were withdrawn and stimuli made freely available, the number of effective competing stimuli increased in all 6 cases. Findings suggest that procedures designed to promote engagement and disrupt problem behavior may allow the A-CSA to be a platform not only for identifying competing stimuli, but also for actively establishing competing stimuli.

Three experiments explored the impact of different reinforcer rates for alternative behavior (DRA) on the suppression and post-DRA relapse of target behavior, and the persistence of alternative behavior. All experiments arranged baseline, intervention with extinction of target behavior concurrently with DRA, and post-treatment tests of resurgence or reinstatement, in two- or three-component multiple schedules. Experiment 1, with pigeons, arranged high or low baseline reinforcer rates; both rich and lean DRA schedules reduced target behavior to low levels. When DRA was discontinued, the magnitude of relapse depended on both baseline reinforcer rate and the rate of DRA. Experiment 2, with children exhibiting problem behaviors, arranged an intermediate baseline reinforcer rate and rich or lean signaled DRA. During treatment, both rich and lean DRA rapidly reduced problem behavior to low levels, but post-treatment relapse was generally greater in the DRA-rich than the DRA-lean component. Experiment 3, with pigeons, repeated the low-baseline condition of Experiment 1 with signaled DRA as in Experiment 2. Target behavior decreased to intermediate levels in both DRA-rich and DRA-lean components. Relapse, when it occurred, was directly related to DRA reinforcer rate as in Experiment 2. The post-treatment persistence of alternative behavior was greater in the DRA-rich component in Experiment 1, whereas it was the same or greater in the signaled-DRA-lean component in Experiments 2 and 3. Thus, infrequent signaled DRA may be optimal for effective clinical treatment.

The cause of the high degree of variability in cognition and behavior among individuals with Down syndrome (DS) is unknown. We hypothesized that birth defects requiring surgery in the first years of life (congenital heart defects and gastrointestinal defects) might affect an individual's level of function. We used data from the first 234 individuals, age 6-25 years, enrolled in the Down Syndrome Cognition Project (DSCP) to test this hypothesis. Data were drawn from medical records, parent interviews, and a cognitive and behavior assessment battery. Results did not support our hypothesis. That is, we found no evidence that either birth defect was associated with poorer outcomes, adjusting for gender, race/ethnicity, and socioeconomic status. Implications for study design and measurement are discussed.

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Self-injurious behaviour (SIB) is generally considered to be the product of interactions between dysfunction stemming from the primary developmental disability and experiences that occasion and reinforce SIB. As a result of these complex interactions, SIB presents as a heterogeneous problem. Recent research delineating subtypes of SIB that are nonsocially mediated, including one that is amenable to change and one that is highly invariant, enables classification of SIB across a broader continuum of relative environmental-biological influence. Directly examining how the functional classes of SIB differ has the potential to structure research, will improve our understanding this problem, and lead to more targeted behavioural and pharmacological interventions. Recognising that SIB is not a single entity but is composed of distinct functional classes would better align research with conceptual models that view SIB as the product of interactions between environmental and biological variables.

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Severe problem behavior (e.g., self-injury and aggression) remains among the most serious challenges for the habilitation of persons with intellectual disabilities and is a significant obstacle to community integration. The current standard of behavior analytic treatment for problem behavior in this population consists of a functional assessment and treatment model. Within that model, the first step is to assess the behavior–environment relations that give rise to and maintain problem behavior, a functional behavioral assessment. Conventional methods of assessing behavioral function include indirect, descriptive, and experimental assessments of problem behavior. Clinical investigators have produced a rich literature demonstrating the relative effectiveness for each method, but in clinical practice, each can produce ambiguous or difficult-to-interpret outcomes that may impede treatment development. This paper outlines potential sources of variability in assessment outcomes and then reviews the evidence on strategies for avoiding ambiguous outcomes and/or clarifying initially ambiguous results. The end result for each assessment method is a set of best practice guidelines, given the available evidence, for conducting the initial assessment.