Reinforcer pathology,probabilistic choice,and medication adherence in patients with multiple sclerosis

The reinforcer pathology model posits that core behavioral economic mechanisms, including delay discounting and behavioral economic demand, underlie adverse health decisions and related clinical disorders. Extensions beyond substance use disorder and obesity, however, are limited. Using a reinforcer pathology framework, this study evaluates medical adherence decisions in patients with multiple sclerosis. Participants completed behavioral economic measures, including delay discounting, probability discounting, and a medication purchase task. A medical decision-making task was also used to evaluate how sensitivity to mild side effect risk and efficacy contributed to the likelihood of taking a hypothetical disease-modifying therapy. Less steep delay discounting and more intense (greater) medication demand were independently associated with greater adherence to the medication decision-making procedure. More generally, the pattern of interrelations between the medication-specific and general behavioral economic metrics was consistent with and contributes to the reinforcer pathology model. Additional research is warranted to expand these models to different populations and health behaviors, including those of a positive health orientation (i.e., medication adherence).     

The role of effort type and intensity in children's decisions about effort-based outcomes

Despite the importance of persistence in early learning, we know little about how children reason about outcomes that result from their efforts. Here we examined the role of effort type (i.e., physical vs. cognitive) and intensity (i.e., high vs. low effort) in shaping children's decision making about effort-based rewards. Five- to 7-year-olds (N = 133) were assigned to one of four conditions (High Physical Effort, Low Physical Effort, High Cognitive Effort, Low Cognitive Effort) and completed a series of tasks to construct a toy. Tasks varied in the type (physical/cognitive) and intensity (high/low) of effort required to complete them. After constructing their toy, children completed a series of tasks to probe how much they valued that toy. Across conditions, children preferred their toy and gave it a higher monetary value, relative to a stranger's. However, when choosing their toy came at a cost, children no longer preferred it. Only children who built their toy through either cognitive or low effort were willing to incur a cost for their toy. Older children, across conditions, were also more likely to incur a cost for their toy. These findings demonstrate that by age five, children are sensitive to variations in effort type and intensity, and these factors shape how they evaluate effort-based rewards.     

Subjective probability and delay.

Human subjects indicated their preference between a hypothetical $1,000 reward available with various probabilities or delays and a certain reward of variable amount available immediately. The function relating the amount of the certain-immediate reward subjectively equivalent to the delayed $1,000 reward had the same general shape (hyperbolic) as the function found by Mazur (1987) to describe pigeons' delay discounting. The function relating the certain-immediate amount of money subjectively equivalent to the probabilistic $1,000 reward was also hyperbolic, provided that the stated probability was transformed to odds against winning. In a second experiment, when human subjects chose between a delayed $1,000 reward and a probabilistic $1,000 reward, delay was proportional to the same odds-against transformation of the probability to which it was subjectively equivalent.     

Discerning Mouse Trajectory Features With the Drift Diffusion Model

Mouse tracking, a new action-based measure of behavior, has advanced theories of decision making with the notion that cognitive and social decision making is fundamentally dynamic. Implicit in this theory is that people's decision strategies, such as discounting delayed rewards, are stable over task design and that mouse trajectory features correspond to specific segments of decision making. By applying the hierarchical drift diffusion model and the Bayesian delay discounting model, we tested these assumptions. Specifically, we investigated the extent to which the “mouse-tracking” design of decision-making tasks (delay discounting task, DDT and stop-signal task, SST) deviate from the standard “keypress” design of decision making tasks. We found remarkable agreement in delay discounting rates (intertemporal impatience) obtained in the keypress and mouse-tracking versions of DDT (ρ = 0.90) even though these tasks were given about 1 week apart. Rates of evidence accumulation converged well in the two versions (DDT, ρ = .86; SST, ρ = .55). Omission/commission error in SST showed high agreement (ρ = .42, ρ = .53). Mouse-motion features such as maximum velocity and AUC (area under the curve) correlated well with nondecision time (ρ = −.42) and boundary separation (ρ = .44)—the amount of information needed to accumulate prior to making a response. These results indicate that the response time (RT) and motion-based decision tasks converge well at a fundamental level, and that mouse-tracking features such as AUC and maximum velocity do indicate the degree of decision conflict and impulsivity.     

拖延行为的发展认知机制及神经基础

拖延是指尽管预见到拖延会带来不利后果, 人们仍自愿推迟开始或完成某一计划好的任务。研究表明, 不同文化背景下有15%~20%的成年人存在慢性拖延, 超过70%的学生承认自己存在学业拖延, 部分学生还会形成特质性拖延。严重的拖延不仅影响人们的学业、工作和生活, 甚至还会危害到人们的身心健康。鉴于目前对于拖延产生的核心机制、形成的关键期以及发展认知神经机制还不是很清楚, 本项目拟从拖延的时间决策理论出发, 首先系统探明拖延决策的核心机制, 尤其是远期价值评估、延迟折扣和自我控制能力等在拖延决策过程中的认知加工机制和神经基础; 其次结合行为-环境变量-脑的多模态数据, 从发展角度探究拖延形成的关键期(敏感期)、影响因素以及发展认知神经机制; 最后从行为干预和脑的可塑性角度出发, 试图制定各关键年龄阶段拖延预防与干预的临床方案。本研究的开展对于把握拖延形成的认知机制、神经基础及其发展规律具有重要的科学价值, 对于拖延行为的预防和干预也具有直接的现实意义。     

Relationships between perfectionism,self-report impulsivity measures and delay discounting

Perfectionism and impulsivity are multidimensional constructs. While different perfectionism dimensions are exclusively measured through self-reports, different impulsivity dimensions can be measured through self-report or behaviour via preferences for different rewards. This study explored differential associations between perfectionism and impulsivity based on both dimension and measurement modality (self-report/behavioural). We then examined whether adaptive or maladaptive perfectionism would be differentially associated with impulsivity. Two-hundred and six students completed two perfectionism and three impulsivity measures (two self-report; one behavioural). Two self-report impulsivity measures were associated with specific perfectionism dimensions, whereas the behavioural measure was not associated with perfectionism. Maladaptive perfectionism was associated with decreasing impulsivity, whereas adaptive perfectionism was associated with increasing impulsivity. Perfectionism related to impulsivity differently depending on how each construct was measured.     

Do behavioral measures of self-control assess construct-level variance?

A wide range of measures have been used to assess self-control including executive function tasks, delay of gratification tasks, and persistence and willpower tasks. The current study sought to examine the convergent and predictive validity of these measures, provide theoretical backing for why we might or might not expect high correlations between different indicators of the construct, and question whether such measures are assessing construct-level variance. The results largely replicated prior research, with the majority of correlations being small in magnitude and non-significant. Possible interpretations include indicators assessing distinct and unrelated subdomains of self-control, the inappropriate use of measures that maximize within person variance, indicators being plagued by large sources of error variance, or some combination of these.     

Examining children's ability to delay reward: Is the delay discounting task a suitable measure?

Discounting the value of delayed rewards has primarily been measured in children with the delay of gratification task and in adolescents and adults with the delay discounting task. In the present study, we assessed the suitability of the delay discounting task as a measure of temporal discounting in children. A sample of 7- to 9-year-olds (N = 98) completed a delay discounting task, a delay of gratification task, a sensation seeking measure, and IQ measures. In addition, teacher-based assessments of attention-deficit/hyperactivity disorder traits were measured. The results indicated that the majority of children produced meaningful data on the discounting task and discounted rewards hyperbolically. Children with an elevated risk of attention-deficit/hyperactivity disorder showed a trend towards discounting future rewards on the delay discounting task more steeply than did those at low risk. However, delay discounting was unrelated to either delay of gratification or sensation seeking. We interpret these results as providing some support for the use of delay discounting as a measure of intertemporal choice in children, although the results also suggest that delay discounting and delay of gratification tasks may tap different processes in this population.     

Transitional and steady-state choice behavior under an adjusting-delay schedule

Twelve rats made repeated choices on an adjusting-delay schedule between a smaller reinforcer (A) that was delivered immediately after a response and a larger reinforcer (B) that was delivered after a delay which increased or decreased by 20% depending on the subject's choices in successive blocks of trials. In two phases of the experiment (100 sessions and 40 sessions), reinforcer sizes were selected which enabled theoretical parameters expressing the rate of delay discounting and sensitivity to reinforcer size to be estimated from the ratio of the indifference delays obtained in the two phases. Indifference delays, calculated from adjusting delays in the last 10 sessions of each phase, were shorter when the sizes of A and B were 14 and 25 μl of a 0.6 M sucrose solution than when they were 25 and 100 μl of the same solution. The ratio of the indifference delays was significantly smaller than that predicted on the basis of an assumed linear relation between reinforcer size and instantaneous reinforcer value, consistent with a previous proposal that this relation may be hyperbolic in form. Estimates of the rate of delay discounting based on the ratio of the two indifference delays (mean, 0.08 s(-1)) were similar to values obtained previously using different intertemporal choice protocols. Estimates of the size-sensitivity parameter (mean 113 μl) were similar to estimates recently derived from performance on progressive-ratio schedules. In both phases of the experiment, adjusting delays in successive blocks of trials were analyzed using the Fourier transform. The power spectrum obtained from individual rats had a dominant frequency that corresponded to a period of oscillation of the adjusting delay between 30 and 100 trial blocks (mean, 78). Power in the dominant frequency band was highest in the early sessions of the first phase and declined with extended training. It is suggested that this experimental protocol may have utility in neurobehavioral studies of intertemporal choice.