Contingency Enhances Sensitivity to Loss in a Gambling Task with Diminishing Returns.

This study examined whether gambling behavior under conditions of diminishing returns differed between participants with histories of contingent (CD group) and noncontingent (NCD group) token delivery. In Phase 1, CD participants accrued tokens by correctly completing a discrimination task; for NCD participants, token accrual was yoked to token delivery of CD participants. In Phase 2, participants could choose to gamble their tokens or end the experiment and exchange their tokens for money. During the gambling task, participants could bet one token per trial. The probability of losses began at 10% and increased incrementally across blocks of 10 trials up to 100%. Overall, participants in the CD group gambled on fewer trials than participants in the NCD group. Costs of token accrual during Phase 1, in terms of number of trials and duration, showed a positive correlation with net tokens for the CD group but not the NCD group. Results are consistent with previous research demonstrating the value-enhancing effects of both prior contingent delivery and effort, and offer evidence that these histories influence sensitivity to loss.

Individualized sampling parameters for behavioral observations: enhancing the predictive validity of competing stimulus assessments.

Recent studies have used pretreatment analyses, termed competing stimulus assessments, to identify items that most effectively displace the aberrant behavior of individuals with developmental disabilities. In most studies, there appeared to have been no systematic basis for selecting the sampling period (ranging from 30 s to 10 min) in which items were assessed. Unfortunately, estimates based on brief samples of behavior do not always predict the extent to which items will displace aberrant behavior over longer periods. This study first examined a method for determining an accurate individualized sample length for competing stimulus assessments, based on statistical measures of correspondence with extended effects, using a small number of items. The effects of a larger number of items were then assessed using the determined sample length. Finally, the method was validated by comparing its predictions, in terms of the reduction of problem behavior over more extended periods, to predictions based on sample durations typically used in previous investigations. For two participants, predictions based on individualized determination of sample lengths were more accurate than predictions based on typical sample lengths. These results are discussed in terms of the exchange between expediency and accuracy during competing stimulus assessments.

A comparison of dense-to-lean and fixed lean schedules of alternative reinforcement and extinction.

Behavior-reduction interventions typically employ dense schedules of alternative reinforcement in conjunction with operant extinction for problem behavior. After problem behavior is reduced in the initial treatment stages, schedule thinning is routinely conducted to make the intervention more practical in natural environments. In the current investigation, two methods for thinning alternative reinforcement schedules were compared for 3 clients who exhibited severe problem behavior. In the dense-to-lean (DTL) condition, reinforcement was delivered on relatively dense schedules (using noncontingent reinforcement for 1 participant and functional communication training for 2 participants), followed by systematic schedule thinning to progressively leaner schedules. During the fixed lean (FL) condition, reinforcement was delivered on lean schedules (equivalent to the terminal schedule of the DTL condition). The FL condition produced a quicker attainment of individual treatment goals for 2 of the 3 participants. The results are discussed in terms of the potential utility of using relatively lean schedules at treatment outset.

Re-evaluation of constant versus varied punishers using empirically derived consequences.

Charlop, Burgio, Iwata, and Ivancic [J. Appl. Behav. Anal. 21 (1988) 89] demonstrated that varied punishment procedures produced greater or more consistent reductions of problem behavior than a constant punishment procedure. More recently, Fisher and colleagues [Res. Dev. Disabil. 15 (1994) 133; J. Appl. Behav. Anal. 27 (1994) 447] developed a systematic methodology for predicting the efficacy of various punishment procedures. Their procedure identified reinforcers and punishers (termed "empirically derived consequences" or EDC) that, when used in combination, reduced the destructive behavior of individuals with developmental disabilities who displayed automatically maintained destructive behavior. The current investigation combines these two lines of research by comparing the effects of constant versus varied punishers on the self-injury of two individuals with developmental disabilities. The punishing stimuli were selected via the procedures described by Fisher et al. and were predicted to be at varying levels of effectiveness. The varied presentation of punishers resulted in enhanced suppressive effects over the constant presentation of a punisher for one of two individuals, but only in comparison to a single stimulus predicted to be minimally effective. Even then, the differences were small. These results suggest that the additive effects of varied punishment are negligible if clinicians use stimuli predicted to be effective and are discussed in terms of the conditions under which stimulus variation could potentially enhance the effects of punishers.

Assessing psychopathology in individuals with developmental disabilities.

Individuals with developmental disabilities are at high risk for developing mental health problems. The prevalence of psychopathology is approximately 4 times higher than that found in the general population. Yet there is a tendency to underdiagnose psychiatric disorders in the developmentally delayed population because of diagnostic overshadowing, the lack of appropriate diagnostic criteria, and the paucity of appropriate assessment measures. Over the past decade, there has been an emergence of scales developed specifically to screen for psychopathology in individuals with developmental disabilities. In addition, advancements have been made in observation techniques, thus facilitating the ability to objectively observe behaviors often described as internal events. A description of a multimethod approach to assessing psychopathology in individuals with developmental disabilities is provided incorporating the recent advancements in the field, as well as suggestions for future research.