External Validity of Conduct and Oppositional Defiant Disorders Determined by the NIMH Diagnostic Interview Schedule for Children

We administered the Diagnostic Interview Schedule for Children (DISC) two times to a group of youth (222 boys, 147 girls) entering residential care, once at their time of entry and once 1 year later. We then compared their DISC outcomes on Conduct Disorder (CD) and Oppositional Defiant Disorder (ODD) against changes in independent direct observations of diagnostically relevant behavior obtained over the course of that year. Results from hierarchical linear modeling analyses showed significant discriminative relationships between results from the DISC and the independent observations. Specifically, observations of symptomatic behaviors (CD or ODD) decreased for youth who met diagnostic criteria at the first administration of the DISC but not at the second, increased for youth who did not meet criteria at the first administration but did at the second, and did not change for youth who met criteria at both administrations. These results extend the data on the validity of the DISC and support continued research efforts to determine its clinical utility.     

Countering conspiracy theory beliefs: Understanding the conjunction fallacy and considering disconfirming evidence

Research suggests that a number of cognitive processes—including pattern perception, intentionality bias, proportionality bias, and confirmation bias—may underlie belief in a conspiracy theory. However, there are reasons to believe that conspiracy theory beliefs also depend in part on a failure to understand the probability of actual events allegedly supporting those conspiracy theories as well as a failure to entertain disconfirming evidence that may contradict those beliefs. Study 1 examines the relationships between general beliefs in conspiracy theories, belief in a novel conspiracy theory, conjunctive error propensity, and the propensity to consider disconfirming evidence. Study 2 investigates the roles of confronting both the propensity to make conjunctive errors and the failure to consider disconfirming evidence in changing conspiracy theory beliefs as well as attitudes associated with those beliefs. The results of both studies suggest that corrections to one's propensity to make conjunctive errors and mindful consideration of disconfirming evidence may serve as viable methods of self-persuasion pertaining to conspiracy theory beliefs.     

Effects consistent with behavioral contrast during a multiple schedule for discrimination training on mands for attention

This study used a multiple schedule to assess the effects of an S+ or S- in the absence of rules on excessive mand rates with three school-aged children with disabilities and assessed possible contrast effects occurring in conjunction with the intervention. Each of the three participants was exposed to the presence or absence of an S- (black baseball cap). When it was worn, mand approach rates decreased for all three participants; conversely, mand rates increased to twice the baseline rates when the experimenter was not wearing the black baseball cap. Generalization probes conducted for one of the three caregivers showed similar changes when the caregiver wore the cap. Results suggest that effects consistent with positive behavioral contrast occurred with all participants.     

Signaled reinforcement effects on fixed-interval performance of rats with lever depressing or releasing as a target response

The effect of a diffuse auditory signal filling a brief delay between a response and reinforcement depends upon the nature of the trained target response. Rats in a signaled condition responded slower than rats in an unsignaled condition if the target response was lever release. If the target response was lever depression, however, rats in the signaled condition responded faster than rats in the unsignaled condition at the end of training     

Tests of transitivity in choices between fixed and variable reinforcer delays.

This experiment tested for transitivity in pigeons' choices between variable-time (VT) and fixed-time (FT) schedules. In a discrete-trials procedure, a subject chose between two alternatives by making a single key peck. Each choice was between a "standard alternative," which was the same schedule throughout a condition, and an "adjusting alternative," in which the delay to reinforcement was systematically increased or decreased many times a session. These adjustments enabled an approximate indifference point to be identified--the value of the adjusting delay at which the subject chose each alternative about equally often. Each test of transitivity involved four conditions. In one, the standard alternative was a variable-time schedule with a 2-s reinforcer, and the adjusting alternative also delivered a 2-s reinforcer. A second condition was similar except that the adjusting alternative delivered a 5-s reinforcer. The indifference point from each of these conditions was then converted to a fixed-time schedule for subsequent comparisons in the third and fourth conditions, respectively. Each of these last two conditions compared one of the fixed-time schedules (based upon the previous conditions and including their different reinforcer durations) with an adjusting schedule that delivered the alternative reinforcer duration, to determine whether the obtained indifference points would be those predicted from the prior alternative-duration comparisons with the VT schedule. There was little evidence for intransitivity of choice: Averaged across subjects and replications, the obtained indifference points deviated from perfect transitivity by less than 8%, and these deviations were not statistically significant. These results contrast with those of Navarick and Fantino (1972), who found frequent violations of transitivity between periodic and aperiodic schedules using a concurrent-chains procedure with variable-interval schedules in the initial links.     

Cocaine tolerance: acute versus chronic effects as dependent upon fixed-ratio size.

The effects of cocaine on operant behavior were studied by examining fixed-ratio value as a factor in the development of tolerance. Pigeons pecked a response key under a three-component multiple schedule, with each bird being exposed to fixed-ratio values that were categorized as small, medium, or large. Administered acutely, cocaine (1.0 to 10.0 mg/kg) produced dose-related decreases in overall rate of responding. Responding maintained by the largest ratio was decreased by lower doses than those required to reduce rates of responding maintained by the other two ratio schedules. Following repeated daily administration of 5.6 mg/kg of cocaine, dose-effect functions (obtained from sessions during the chronic regimen by making substitutions for the daily dose) indicated tolerance under the smaller ratios, but no tolerance or less tolerance under the largest ratio. Thus, whether tolerance developed, and the degree to which it developed, depended on the ratio value. The results are partially consistent with the notion that tolerance to drug effects on schedule-controlled behavior will develop if drug administration initially reduces reinforcement frequency, but they indicate that reinforcement loss alone is not a sufficient condition for the generation of tolerance under such conditions. The findings suggest that amount of responding required for reinforcement, or "effort," may contribute to the development of tolerance to effects of cocaine.     

Remote effects of aversive contingencies: Disruption of appetitive behavior by adjacent avoidance sessions

Disruption of ongoing appetitive behavior before and after daily avoidance sessions was examined. After baselines of appetitive responding were established under a fixed-interval 180-s schedule of food presentation, 4 rats were exposed to 40-min sessions of the appetitive schedule just prior to 100-min sessions of electric shock postponement, while another 4 rats received the 40-min appetitive sessions just following daily sessions of shock postponement. In all 8 subjects, fixed-interval response rates decreased relative to baseline levels, the effect being somewhat more pronounced when the avoidance sessions immediately followed. The disruption of fixed-interval responding was only partially reversed when avoidance sessions were discontinued. During the initial exposure to the avoidance sessions, patterns of responding under the fixed-interval schedule were differentially sensitive to disruption, with high baseline response rates generally more disturbed than low rates. These disruptions were not systematically related to changes in reinforcement frequency, which remained fairly high and invariant across all conditions of the experiment; they were also not systematically related to the response rates or to the shock rates of the adjacent avoidance sessions. The results, while qualitatively resembling patterns of conditioned suppression as typically studied, occurred on a greatly expanded time scale. As disruption of behavior extending over time, the present data suggest that some forms of conditioned suppression are perhaps best viewed within a larger temporal context.     

Concurrent variable-ratio schedules: Implications for the generalized matching law

Rats' responses were reinforced on concurrent variable-ratio variable-ratio schedules in which responses on one lever incremented the ratio counter and responses on a second lever changed the schedule and correlated stimulus. The relative frequency of reinforcement was varied from .10 to .99. In one set of conditions, responding on the main lever incremented both ratio counters, but reinforcement required a response in the presence of the stimulus correlated with the ratio that had been completed. In a second set of conditions, responses on the main lever incremented only the ratio correlated with the stimulus that was currently present. When main-lever responses incremented both ratio counters, subjects distributed responding and time in a manner consistent with the generalized matching law. When responses on the main lever incremented only the schedule currently in effect, the rats responded almost exclusively on the schedule producing the higher frequency of reinforcement. These results extend the applicability of the generalized matching law to dependent ratio schedules.     

Easy bayes estimation for rasch-type models

A Bayes estimation procedure is introduced that allows the nature and strength of prior beliefs to be easily specified and modal posterior estimates to be obtained as easily as maximum likelihood estimates. The procedure is based on constructing posterior distributions that are formally identical to likelihoods, but are based on sampled data as well as artificial data reflecting prior information. Improvements in performance of modal Bayes procedures relative to maximum likelihood estimation are illustrated for Rasch-type models. Improvements range from modest to dramatic, depending on the model and the number of items being considered.This research was supported by ORN Contact #00014-86-K0087. We wish to thank Sheng-Hui Chu and Dzung-Ji Lii for providing intelligent and energetic programming support for this article. We also thank one of the reviewers for pointing out several interesting and useful perspectives.     

Molecular analyses of the effects of d-amphetamine on fixed-interval schedule performances of rats.

A series of doses (0.5 to 2.0 mg/kg) of d-amphetamine was administered to rats whose lever pressing was maintained by fixed-interval 30-s, 60-s, or 120-s schedules of reinforcement by sucrose delivery. Under both saline and d-amphetamine conditions, molecular features of responding were reliably described in terms of the distribution of postreinforcement pauses and local response rate following the onset of responding. Postreinforcement pause always varied from interval to interval but, on average, shortened under the drug. Local response rate (response rate exclusive of pause time) tended to decrease under the drug, and where acceleration occurred within runs of responses, it was reduced by the drug. All of these effects were dose-related. These findings suggest that fixed-interval behavior can be analyzed effectively at a molecular level, and that the effects of d-amphetamine are best described as disruption of temporal discrimination.