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Evaluating the effects of presession drug administration on intertemporal choice in nonhumans is a useful approach for identifying compounds that promote impulsive behavior in clinical populations, such as those prescribed the dopamine agonist pramipexole (PPX). Based on the results of previous studies, it is unclear whether PPX increases rats' impulsive choice or attenuates aspects of stimulus control. The present study was designed to experimentally isolate behavioral processes fundamental to intertemporal choice and challenge them pharmacologically with PPX administration. In Experiment 1, the hypothesis that PPX increases impulsive choice as a result of enhanced sensitivity to reinforcer delays was tested and disconfirmed. That is, acute PPX diminished delay sensitivity in a manner consistent with disruption of stimulus control whereas repeated PPX had no effect on delay sensitivity. Experiments 2 and 3 elaborated upon this finding by examining the effects of repeated PPX on rats' discrimination of response-reinforcer contingencies and reinforcer amounts, respectively. Accuracy of both discriminations was reduced by PPX. Collectively these results provide no support for past studies that have suggested PPX increases impulsive choice. Instead, PPX impairs stimulus control over choice behavior. The behavioral approach adopted herein could be profitably integrated with genetic and other biobehavioral models to advance our understanding of impulsive behavior associated with drug administration.

Delay discounting is the devaluation of rewards that are delayed in time. This phenomenon was first studied with animals in controlled laboratory environments and later translated to human procedures. Though the decrease in value of outcomes as the delay to receipt increases is the same across species (money for humans, food for animals), a number of methodological concerns have been raised about the procedures used to study delay discounting in humans. The Experiential Discounting Task (EDT) was recently developed in order to study delay discounting in humans in a way that is more similar to that used with animals. That is, humans make repeated decisions concerning outcomes they experience within session (delays and rewards). The EDT has proven useful for a variety of reasons including its ability to detect changes in how delayed rewards are discounted as a function of acute alcohol where traditional measures have not. However, this measure has yet to undergo rigorous tests of internal validity and reliability that previous measures of delay discounting have. In two experiments we tested the reliability and internal validity of the EDT. First we assessed the test-retest reliability across seven days. Next we tested whether the way in which choices are presented in the EDT affects choice. In addition, all participants completed a traditional delay discounting task, boredom proneness scale and probability discounting task. Experiment 1 resulted in good test-retest reliability for all tasks, including the EDT and the traditional measure of delay discounting. In Experiment 2 we found that individual performance did not change as a function of how choices were presented. Across both experiments we found no evidence for a correlation between discounting in the EDT and the traditional measure. Though reliable across time we contend, based on the relation to a traditional delay discounting task and the reviewed literature that there is little evidence that the EDT is a valid measure of delay discounting and call for more research to determine what process underlies decision-making in the EDT.

Clinical Trials Questionnaire. Participation in Clinical Trials: Questionnaire items assessing participation in clinical trials, views regarding trial participation, and views regarding participation in multiple trials. (PDF 267 kb)

Clinical Trials Questionnaire. Participation in Clinical Trials: Questionnaire items assessing participation in clinical trials, views regarding trial participation, and views regarding participation in multiple trials. (PDF 267 kb)

Background Clinical trials are necessary for the advancement of cancer treatment and care, however low rates of participation in such trials limit the generalisability of findings. The objective of this study was to examine the proportion of medical oncology outpatients in Australia who are invited and consent to participate in clinical trials and the factors associated with this. Methods A sample of adult medical oncology patients was recruited from three Australian cancer treatment centres. Consenting patients completed two paper-and-pencil surveys; one at the time of consent and another approximately 1 month later. A multivariate logistic regression was conducted to explore factors associated with invitation and participation in a trial. Results Thirty-eight percent (n = 146) of the 383 participants reported they had been invited to take part in a clinical trial. Of those invited, 93% reported consenting to participate in the trial, with the majority indicating that they did not regret their decision (89%). Treatment centre and time since diagnosis were significantly associated with being invited to take part in a clinical trial. None of the factors examined were associated with clinical trial consent rates. Conclusions The main barrier to clinical trial participation is not being invited to do so, with the centre the patient attends being a modifiable determinant of whether or not they are invited. Increasing the resources available to treatment centres to ensure all patients are offered participation in trials they are eligible for may help to improve rates of trial participation. Electronic supplementary material The online version of this article (10.1186/s12885-017-3644-3) contains supplementary material, which is available to authorized users.