Stochastic PERT networks as models of cognition: Derivation of the mean,variance, and distribution of reaction time using Order-of-Processing (OP) diagrams

It is frequently assumed that the mental activity which leads to a given response is made up of separable components or processes. One or more of the processes are assumed to contribute to the time required to respond. Computation of the mean, variance, and distribution of the reaction time is relatively straightforward when all processes are arranged in series or parallel. However, such is not the case when the processes have complex arrangements. A solution to a useful special case of the above problem is proposed. Specifically, it is shown that simple computations yield closed form expressions for the mean, variance, and distribution of reaction time when the processes can be arranged in a stochastic PERT network and when the durations of individual processes are sums of mutually independent, exponentially distributed random variables. The method of solution relies on the construction of an Order-of-Processing (OP) diagram from the original PERT network representation of behavior.     

The organization of spontaneous leg movements in newborn infants

Spontaneous, supine kicking in newborn (2- and 4-week-old) infants is described in terms of its temporal structure, interjoint coordination, and muscle activation characteristics as measured by surface electromyography. Phasic kick movements shoed a constrained temporal organization in the movement, but not the pause phases. Hip, knee, and ankle joints moved in temporal and spatial synchrony, and all three joints showed a rhythmical or periodic organization over time. EMGs revealed antagonist coactivation at the initiation of the flexor movement, but little or not extensor activity. The dorsal muscles, the gastrocnemius and hamstrings, showed less activity than the ventral pair, tibialis anterior and quadriceps. Burst and onset-to-peak durations were also constrained. As a result of neural mechanisms and biomechanical forces, newborn leg movements are structured muscle synergies. This organization has implications both for newborn functioning and for later development.     

ANALYSIS OF FREE-TIME CONTINGENCIES AS POSITIVE VERSUS NEGATIVE REINFORCEMENT

Providing a short break contingent on completed work may increase responding through positive reinforcement (e.g., access to preferred activities) or negative reinforcement (e.g., escape from work). In this investigation, three analyses conducted with a boy with profound mental retardation showed that (a) a 20-s break increased responding more than a positive reinforcer (cola) did, and (b) the reinforcing effects of a 20-s break were affected by the availability of positive reinforcers during the break.     

FURTHER ANALYSIS OF THE RELATIONSHIP BETWEEN SELF-INJURY AND SELF-RESTRAINT

It has been suggested that self-restraint, a phenomenon often correlated with self-injurious behavior (SIB), may be maintained by negative reinforcement in the form of escape from the aversive properties of SIB (e.g., pain). We examined the effects of blocking SIB (and presumably removing any aversive effects) on the self-restraint of a 19-year-old male with severe mental retardation. Consistent with the negative reinforcement hypothesis, blocking SIB resulted in near-zero levels of SIB and moderate reductions in self-restraint.     

Self-reported levels of psychopathology of drug abusers not currently in treatment

This study assessed levels of psychopathology, as measured by the Symptom Checklist-90-Revised, of drug users not in treatment. These levels were then compared with levels of psychopathology reported previously in the literature of drug users in treatment, the general population, psychiatric inpatients, and psychiatric outpatients. Results suggest that drug users not in treatment endorse significantly lower levels of psychopathology than drug users in treatment, psychiatric inpatients, and psychiatric outpatients. However, they endorse significantly higher levels of pathology than adult nonpatients and they appear most similar to adolescent nonpatients. Implications for clinical work (prevention and intervention) as well as for future research are discussed. The study also established preliminary cultural validity of SCL-90-R with Alaska Natives.     

Religiousness,Religious Orientation,and Attitudes Towards Gays and Lesbians1

Two studies are reported that examine the relationships among religiousness, religious orientation, and prejudice toward gays and lesbians. Study 1 reports the results of a survey done for the purposes of scientific jury selection. These results suggest that Baptists, fundamentalists, and “Christians” display more antigay prejudice than do Catholics, Jews, and many Protestant denominations, but even many supporters of gay-tolerant religions show more antigay prejudice than those claiming no religious preference. Among those with a religious preference, frequency of worship is significantly related to antigay prejudice among those belonging to antigay denominations, but not among those belonging to more gay tolerant religious faiths. Study 2 reports the results of a study of college students regarding religiousness, religious orientation, and prejudice toward gays and lesbians. Results showed that self reported religiousness, frequency of worship, and Batson's internal and external scales were all positively correlated with measures of prejudice toward gays and lesbians, whereas scores on the Quest (Interactional) scale were negatively correlated. Results of both studies strongly challenge the view that those with an intrinsic religious orientation are unprejudiced. It is argued that a social influence process can account for the role played by religious practice and beliefs in creating and maintaining negative attitudes toward gays and lesbians.     

A PRELIMINARY EVALUATION OF EMPIRICALLY DERIVED CONSEQUENCES FOR THE TREATMENT OF PICA

Individualized treatment packages were developed for 3 children with high-rate severe pica using a discrimination training paradigm and a behavioral assessment-based procedure known as empirically derived consequences. Children received empirically derived reinforcers for eating under appropriate stimulus conditions (i.e., eating food only from a plate and placemat that served as a discriminative stimulus) and empirically derived punishers for attempts to engage in pica. This treatment package resulted in marked reductions in pica and an increase in appropriate eating for all 3 children in a “baited” analogue condition. In addition, low rates of pica were maintained for 9 months for all 3 children. These results suggest that treatment effectiveness may be enhanced when behavioral assessment data are used to identify potent consequences.     

Using empowerment theory in collaborative partnerships for community health and development

Models of community empowerment help us understand the process of gaining influence over conditions that matter to people who share neighborhoods, workplaces, experiences, or concerns. Such frameworks can help improve collaborative partnerships for community health and development. First, we outline an interactive model of community empowerment that describes reciprocal influences between personal or group factors and environmental factors in an empowerment process. Second, we describe an iterative framework for the process of empowerment in community partnerships that includes collaborative planning, community action, community change, capacity building, and outcomes, and adaptation, renewal, and institutionalization. Third, we outline activities that are used by community leadership and support organizations to facilitate the process of community empowerment. Fourth, we present case stories of collaborative partnerships for prevention of substance abuse among adolescents to illustrate selected enabling activities. We conclude with a discussion of the challenges and opportunities of facilitating empowerment with collaborative partnerships for community health and development. This work was supported by Kansas Health Foundation Grants 9206032B and 9206032A to support and evaluate community partnerships to prevent adolescent substance abuse. Thanks to Tom Wolff for sharing his wisdom about community coalitions so generously, and to Bill Berkowitz and anonymous reviewers for thoughtful comments on an earlier version of this manuscrpt. We also thank our colleagues from the Kansas Health Foundation, Mary K. Campuzano, Steve Coen, and Marni Vliet, and those from collaborating communities, who continue to teach us about ways to enhance community capacities to address local concerns.     

INCREASING GENERALIZED SOCIAL INTERACTIONS IN PSYCHOTIC AND MENTALLY RETARDED RESIDENTS THROUGH PEER-MEDIATED THERAPY

This study investigated whether withdrawn adults living in a residential center for psychotic and mentally handicapped persons could serve as peer therapists to increase the social interaction of other withdrawn residents. Two pairs of residents served as participants. Treatments were introduced and evaluated within a multiple baseline with reversal design. After baseline, the peer therapist was instructed to increase the social interactions of a target peer through engagement in social interactions. The results demonstrated that the peer therapist increased the social interactions of target peers. However, these increases did not generalize to other residents until the introduction of a multiple peer therapist condition. The percentage of time the peer therapists interacted with other nontarget residents also increased throughout the study. These results were maintained during a 4-month follow-up condition.     

A COMPARISON OF TWO APPROACHES FOR IDENTIFYING REINFORCERS FOR PERSONS WITH SEVERE AND PROFOUND DISABILITIES

The development of effective training programs for persons with profound mental retardation remains one of the greatest challenges for behavior analysts working in the field of developmental disabilities. One significant advancement for this population has been the reinforcer assessment procedure developed by Pace, Ivancic, Edwards, Iwata, and Page (1985), which involves repeatedly presenting a variety of stimuli to the client and then measuring approach behaviors to differentiate preferred from nonpreferred stimuli. One potential limitation of this procedure is that some clients consistently approach most or all of the stimuli on each presentation, making it difficult to differentiate among these stimuli. In this study, we used a concurrent operants paradigm to compare the Pace et al. (1985) procedure with a modified procedure wherein clients were presented with two stimuli simultaneously and were given access only to the first stimulus approached. The results revealed that this forced-choice stimulus preference assessment resulted in greater differentiation among stimuli and better predicted which stimuli would result in higher levels of responding when presented contingently in a concurrent operants paradigm.