Varying reinforcement magnitude on interval schedules

In Experiment 1, rats were trained on either a random-interval or a variable-interval 60-sec schedule of reinforcement, and reinforcement magnitude was varied across conditions between one and four pellets. Although the two schedules maintained different patterns of behaviour, patterns and rates of responding were not systematically affected by the variation in reinforcement magnitude. In Experiment 2, a regulated probability interval schedule that generated similar rates of reinforcement to those of the schedules of Experiment 1 was used, with the pattern of behaviour generated resembling that typical of a random-interval schedule. Changing reinforcement magnitude again produced few systematic changes in behaviour. In Experiment 3, a variable-ratio schedule was used within a procedure that otherwise resembled that of Experiments 1 and 2. Increasing the reinforcement magnitude now decreased the rates of responding, and examination of the patterns of responding showed that this came about because rates of responding were higher early in the interreinforcer interval in the one-pellet condition. These experiments demonstrate the insensitivity of behaviour under interval schedules to changes in reinforcement magnitude and suggest the operation of mechanisms different from those engaged by ratio schedules and discretetrial learning procedures.     

Lifestyle interventions in the treatment of childhood overweight: a meta-analytic review of randomized controlled trials.

CONTEXT: Evaluating the efficacy of pediatric weight loss treatments is critical. OBJECTIVE: This is the first meta-analysis of the efficacy of RCTs comparing pediatric lifestyle interventions to no-treatment or information/education-only controls. DATA SOURCES: Medline, PsycINFO, and Cochrane Controlled Trials Register. STUDY SELECTION: Fourteen RCTs targetting change in weight status were eligible, yielding 19 effect sizes. DATA EXTRACTION: Standardized coding was used to extract information on design, participant characteristics, interventions, and results. DATA SYNTHESIS: For trials with no-treatment controls, the mean effect size was 0.75 (k = 9, 95% confidence interval [CI] = 0.52-0.98) at end of treatment and 0.60 (k = 4, CI = 0.27-0.94) at follow-up. For trials with information/education-only controls, the mean ES was 0.48 (k = 4, CI = 0.13-0.82) at end of treatment and 0.91 (k = 2, CI = 0.32-1.50) at follow-up. No moderator effects were identified. CONCLUSIONS: Lifestyle interventions for pediatric overweight are efficacious in the short term with some evidence for extended persistence. Future research is required to identify moderators and mediators and to determine the optimal length and intensity of treatment required to produce enduring changes in weight status.     

Perceptions of Sexual Harassment as a Function of Target's Response Type and Observer's Sex

Although research has investigated definitionsand prevalence of sexual harassment, little is knownabout responses to sexual harassment. Therefore, thepresent study was designed to explore how individuals interpret the communication of various targetresponses. One hundred and twenty employees fromhealthcare settings were randomly assigned to one offour conditions. The majority of the individuals in the sample was White-European American (75%) whilethe remaining 25% was comprised of minority members. Theconditions contained a video-taped interaction betweentwo co-workers, one male and one female. The male's behavior in each interaction continuedto escalate to the point of sexual harassment while thefemale's responses varied. There were two passiveresponses and two assertive responses. After viewing the short video participants responded toquestions assessing their perceptions of theinteraction. Results indicated there were no differencesin perceptions between men and women when viewing thevarious conditions. There were, however, differencesfound between the assertive conditions and the passiveconditions. Specifically, assertive responses areperceived as more effective than passive responses in communicating unwelcomeness and in deterringthe initiator's persistence. However, consistent withthe research on responses to sexual harassment,perceptions of sexual harassment appear to be based more on the initiator's behavior than on thetarget's responses.