The schedule dependency of the signaled reinforcement effect

In Experiment 1, rats leverpressed for food reinforcement on either a variable ratio (VR) 30 schedule or a variable interval (VI) 15-s schedule. One group in each condition received a signal filling a 500-ms delay of reinforcement. This treatment enhanced rates on the VR schedule, and attenuated rates on the VI schedule, relative to the rate seen in an unsignaled control condition. In Experiment 2 there was no delay of reinforcement and the signal and food were presented simultaneously. Attenuated rates of responding were observed on VI schedules with a range of mean interval values (15 to 300 s). Experiment 3 used a range of VR schedules (10 to 150) with simultaneous presentations of signal and food. A signal-induced enhancement of response rate was found at all VR values. In Experiment 4, a signal elevated response rates on a tandem VI VR schedule, but depressed rates on a tandem VR VI schedule, compared to control conditions receiving unsignaled delayed reinforcement. These results are taken to show that the effect of a signal accompanying reinforcement depends upon the nature of the behavior that is reinforced during exposure to a given schedule.     

Visual Reinforcement Signals Interfere with the Effects of Reinforcer Magnitude Manipulations

Three experiments examined the effect of reinforcement magnitude on free-operant response rates. In Experiment 1, rats that received four food pellets responded faster than rats that received one pellet on a variable ratio 30 schedule. However, when the food hopper was illuminated during reinforcer delivery, there was no difference between the rates of response produced by the two magnitudes of reward. In Experiment 2, there was no difference in response rates emitted by rats receiving either one or four pellets of food as reward on a random interval (RI) 60-s schedule. In Experiment 3, rats responding on an RI 30-s schedule did so at a lower rate with four pellets as reinforcement than with one pellet. This effect was abolished by the illumination of the food hopper during reinforcement delivery. These results indicate that the influence of magnitude is obscured by manipulations which signal the delivery of reinforcement.     

The importance of conduct problems and depressive symptoms in predicting adolescent substance use

The current study assessed the relative importance of conduct problems and depressive symptoms, measured at two ages (11 and 15), for predicting substance use at age 15 in an unselected birth cohort of New Zealand adolescents. Among males, when the relative predictive utility of both conduct problems and depressive symptoms was assessed, only pre-adolescent depressive symptoms were found to predict multiple drug use 4 years later. No predictive relation was found between early symptomatology and later substance use among females. The strongest association between predictors and substance use emerged between age 15 multiple drug use and concurrent conduct problems for both males and females. Finally, both conduct problems and depressive symptoms at age 15 were also found to be associated with concurrent self-medication among females.This work was supported by USPHS grants MH-43746 and MH-45070 from the Antisocial and Violent Behavior Branch of the National Institute of Mental Health to Terrie Moffitt. Bill Henry was funded by a Fulbright Travel Award. The Dunedin Multidisciplinary Health and Development Research Unit is supported by the Medical Research Council and Health Research Council of New Zealand. Appreciation is expressed to the interviewers who collected the data, and to the young New Zealanders who were members of the sample.     

Revaluation manipulations produce emergence of underselected stimuli following simultaneous discrimination in humans

Stimulus overselectivity occurs when only one of potentially many aspects of the environment controls behaviour. In four experiments, human participants were trained and tested on a trial-and-error simultaneous discrimination task involving two two-element compound stimuli. Overselectivity emerged in all experiments (i.e., one element from the reinforced compound controlled behaviour at the expense of the other). Following revaluation (extinction) of the previously overselected stimulus, behavioural control by the underselected stimulus element emerged without any direct training of that stimulus element. However, while a series of extinction manipulations targeting the revaluation of the overselected stimulus produced differential extinction of that stimulus, they did not result in differential emergence of the previously underselected stimuli. The results are discussed with respect to the theoretical implications for attention-based accounts of overselectivity.     

Community Matters: Intimate Partner Violence Among Rural Young Adults

Drawing on social disorganization theory, the current study examined the extent to which community-level poverty rates and collective efficacy influenced individual reports of intimate partner violence (IPV) perpetration, victimization, and bystander intervention among a sample of 178 young adults (18–24; 67.4 % women) from 16 rural counties across the eastern US who completed an online survey that assessed demographic information, IPV perpetration, victimization, bystander intervention, and collective efficacy. We computed each county’s poverty rate from the 2007–2011 American Community Survey. Generalized estimating equations demonstrated that after controlling for individual-level income status, community-level poverty positively predicted IPV victimization and perpetration for both men and women. Collective efficacy was inversely related to IPV victimization and perpetration for men; however, collective efficacy was unrelated to IPV victimization and perpetration for women. Whereas IPV bystander intervention was positively related to collective efficacy and inversely related to individual-level income status for both men and women, community-level poverty was unrelated to IPV bystander intervention for both men and women. Overall, these findings provide some support for social disorganization theory in explaining IPV among rural young adults, and underscore the importance of multi-level IPV prevention and intervention efforts focused around community-capacity building and enhancement of collective efficacy.