Resistance to change of forgetting functions and response rates

This experiment examined the effects of reinforcement probability on resistance to change of remembering and response rate. Pigeons responded on a two-component multiple schedule in which completion of a variable-interval 20-s schedule produced delayed matching-to-sample trials in both components. Each session included four delays (0.1 s, 2 s, 4 s, and 8 s) between sample termination and presentation of comparison stimuli in both components. The two components differed in the probability of reinforcement arranged for correct matches (i.e., rich, p = .9; lean, p = .1). Response rates during the variable-interval portion of the procedure were higher in the rich component during baseline and more resistant to the disruptive effects of intercomponent food and extinction. Forgetting functions were constructed by examining matching accuracy as a function of delay duration. Baseline accuracy was higher in the rich component than in the lean component as measured by differences in the gamma-intercept of the forgetting functions (i.e., initial discrimination), rather than from differences in the slope of the forgetting function (i.e., rate of forgetting). Intercomponent food increased the rate of forgetting relatively more in the lean component than in the rich component, but initial discrimination was not systematically affected. Extinction reduced initial discrimination relatively more in the lean component than in the rich component, but did not systematically affect rate of forgetting. These results are consistent with our previous data suggesting that, as for response rate, accuracy and resistance to change of discriminating are positively related to rate of reinforcement. These data also suggest that the disruptability of remembering depends on the conditions of reinforcement, but the way in which remembering is disrupted depends on the nature of the disruptor.     

Effects of response disparity on stimulus and reinforcer control in human detection tasks

In two detection experiments, university students reported whether the second of two sequentially presented tones was longer or shorter than the first by responding to stimuli presented on a touch screen. Stimulus disparity and response disparity were manipulated to compare their effects on measures of discrimination and response bias when the reinforcement ratio for correct responses was asymmetric. Choice stimuli consisted of squares filled with different pixel densities. Response disparity was manipulated by varying the difference in density between the two choice stimuli. In both experiments, decreasing stimulus disparity reduced discrimination but had no consistent effect on bias. Decreasing response disparity also reduced discrimination in both experiments, and often reduced estimates of bias. The effects of response disparity on bias were most clear in Experiment 2, in which a greater overall level of response disparity was arranged. The data show that, like corresponding research with pigeons, detection performance of human subjects can be conceptualized as discriminated operants.     

Prolonged grief disorder symptoms in bereaved internally displaced Tiv persons in Nigeria: associations with rumination,rebirth concerns and gender

ABSTRACT

There is burgeoning research on prolonged grief disorder (PGD) among several vulnerable populations but PGD symptoms have been scarcely examined among bereaved internally displaced persons (IDPs). This study investigated the associations of rumination, rebirth concerns and gender with symptoms of PGD following conflict-related bereavement. Participants were 379 Nigerian IDPs who were of the Tiv ethnic group. They provided demographics and completed self-report measures grief and rumination, while concern about rebirth status of the deceased was assessed using a single item which requested participants to indicate whether they had any concerns about the re-incarnation of the deceased. Results showed that gender was not associated with PGD symptoms. High intrusive rumination and high deliberate rumination were associated with increased PGD symptoms in males and females. Rebirth concern was associated with high PGD symptoms in males but not in females. Findings highlight the need for socio-culturally-informed screening/intervention in the wake of conflict-related bereavement.     

‘In Our Country it's Just Poor People who Ride a Bike’: Place,Displacement and Cycling in Australia

This study investigates relationships and characteristics of participation in cycling in Melbourne, Australia, as an expression of place and displacement among persons from culturally and linguistically diverse origins including Asia (i.e. Vietnam, Sri Lanka and Japan) and Arab Africa (i.e. Saudi Arabia, Eritrea and Sudan). Using a mixed‐method approach, results indicated that despite a significant number of migrants to Australia with origins in places where cycling is a common mode of transport and activity, a large number of newly arrived and marginalised migrants and refugees are less likely to engage in cycling. Cyclists' identity, citizenship, social‐economic marginalisation and residential geographic isolation significantly impacted on their cycling in Melbourne. Although cycling is considered accessible, environmentally friendly, healthy and functional, the results indicated that this view may only represent and be shared by selected citizens. In short, culturally and linguistically diverse participants identified cycling behaviour differently in Australia in comparison with cycling in their countries of origin. The results contribute to knowledge in highlighting the extent of displacement facing marginalised communities that evolves in everyday practices of local mobility. The study identified a number of paradoxes facing mainstream policy makers, researchers and cycling advocates who tend to take cycling participation for granted as non‐political and universal. Copyright © 2014 John Wiley & Sons, Ltd.