The ability to exert self-control is key to social insertion and professional success. An influential literature in psychology has developed the theory that self-control relies on a limited common resource, so that fatigue effects might carry over from one task to the next. However, the biological nature of the putative limited resource and the existence of carry-over effects have been matters of considerable controversy. Here, we targeted the activity of the lateral prefrontal cortex (LPFC) as a common substrate for cognitive control, and we prolonged the time scale of fatigue induction by an order of magnitude. Participants performed executive control tasks known to recruit the LPFC (working memory and task-switching) over more than 6 h (an approximate workday). Fatigue effects were probed regularly by measuring impulsivity in intertemporal choices, i.e., the propensity to favor immediate rewards, which has been found to increase under LPFC inhibition. Behavioral data showed that choice impulsivity increased in a group of participants who performed hard versions of executive tasks but not in control groups who performed easy versions or enjoyed some leisure time. Functional MRI data acquired at the start, middle, and end of the day confirmed that enhancement of choice impulsivity was related to a specific decrease in the activity of an LPFC region (in the left middle frontal gyrus) that was recruited by both executive and choice tasks. Our findings demonstrate a concept of focused neural fatigue that might be naturally induced in real-life situations and have important repercussions on economic decisions.

Subjective well-being or happiness is often associated with wealth. Recent studies suggest that momentary happiness is associated with reward prediction error, the difference between experienced and predicted reward, a key component of adaptive behaviour. We tested subjects in a reinforcement learning task in which reward size and probability were uncorrelated, allowing us to dissociate between the contributions of reward and learning to happiness. Using computational modelling, we found convergent evidence across stable and volatile learning tasks that happiness, like behaviour, is sensitive to learning-relevant variables (i.e., probability prediction error). Unlike behaviour, happiness is not sensitive to learning-irrelevant variables (i.e., reward prediction error). Increasing volatility reduces how many past trials influence behaviour but not happiness. Finally, depressive symptoms reduce happiness more in volatile than stable environments. Our results suggest that how we learn about our world may be more important for how we feel than the rewards we actually receive.

Highlights d Training overload in endurance sport induces cognitive control fatigue d Training-induced fatigue is associated with reduced prefrontal cortex activity d Training-induced fatigue is associated with enhanced choice impulsivity d Excessive physical training and intellectual work induce similar cognitive fatigue

IntroductionWhile several theories have highlighted the importance of the noradrenergic system for behavioral flexibility, a number of recent studies have also shown a role for noradrenaline in motivation, particularly in effort processing. Here, we designed a novel sequential cost/benefit decision task to test the causal influence of noradrenaline on these two functions in rhesus monkeys.MethodsWe manipulated noradrenaline using clonidine, an alpha-2 noradrenergic receptor agonist, which reduces central noradrenaline levels and examined how this manipulation influenced performance on the task. ResultsClonidine had two specific and distinct effects: first, it decreased choice variability, without affecting the cost/benefit trade-off; and second, it reduced force production, without modulating the willingness to work.ConclusionsTogether, these results support an overarching role for noradrenaline in facing challenging situations in two complementary ways: by modulating behavioral volatility, which would facilitate adaptation depending on the lability of the environment, and by modulating the mobilization of resources to face immediate challenges.Electronic supplementary materialThe online version of this article (10.1007/s00213-018-4963-z) contains supplementary material, which is available to authorized users.

When faced with a threat, peoples’ estimate of risk guides their response. When danger is to the self as well as to others two estimates are generated: the risk to oneself and the risk to others. As these estimates likely differ, it is unclear how exactly they drive a response. To answer this question, we studied a large representative sample of Americans facing the COVID-19 pandemic at two time points (N1=1145, N2=683). We discover a paradoxical duality: a tendency to be optimistic about one’s own risk of infection (private optimism) while at the same time to be pessimistic about the risk to others (public pessimism). These two estimates were found to be differentially related to affect and choice. First, private optimism, but not public pessimism, was associated with people’s positive feelings. The association between private optimism and positive affect was mediated by people’s sense of agency over their future. However, negative affect was related to both private risk perception and public risk perception. Second, people predominantly engaged in protective behaviors based on their estimated risk to the population rather than to themselves. This suggests that people were predominantly engaging in protective behaviors for the benefit of others. The findings are important for understanding how people’s beliefs about their own future and that of others are related to protective behaviors and well-being.

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Standard economic indicators provide an incomplete picture of what we value both as individuals and as a society. Furthermore, canonical macroeconomic measures, such as GDP, do not account for non-market activities (e.g., cooking, childcare) that nevertheless impact well-being. Here, we introduce a computational tool that measures the affective value of experiences (e.g., playing a musical instrument without errors). We go on to validate this tool with neural data, using fMRI to measure neural activity in male and female human subjects performing a reinforcement learning task that incorporated periodic ratings of subjective affective state. Learning performance determined level of payment (i.e., extrinsic reward). Crucially, the task also incorporated a skilled performance component (i.e., intrinsic reward) which did not influence payment. Both extrinsic and intrinsic rewards influenced affective dynamics, and their relative influence could be captured in our computational model. Individuals for whom intrinsic rewards had a greater influence on affective state than extrinsic rewards had greater ventromedial prefrontal cortex (vmPFC) activity for intrinsic than extrinsic rewards. Thus, we show that computational modelling of affective dynamics can index the subjective value of intrinsic relative to extrinsic rewards, a 'computational hedonometer' that reflects both behavior and neural activity that quantifies the affective value of experience. SIGNIFICANCE STATEMENTTraditional economic indicators are increasingly recognized to provide an incomplete picture of what we value as a society. Standard economic approaches struggle to accurately assign values to non-3 market activities that nevertheless may be intrinsically rewarding, prompting a need for new tools to measure what really matters to individuals. Using a combination of neuroimaging and computational modeling, we show that despite their lack of instrumental value, intrinsic rewards influence subjective affective state and ventromedial prefrontal cortex activity. The relative degree to which extrinsic and intrinsic rewards influence affective state is predictive of their relative impacts on neural activity, confirming the utility of our approach for measuring the affective value of experiences and other nonmarket activities in individuals.

How to distribute resource consumption over time is a critical optimization problem. If an agent were to consume all available resources, they would be left with insufficient resources in the future. Inversely, if an agent were to save all their resources for later, they might not live long enough to consume them. The first error is common due to “temporal discounting” - the tendency to value immediate rewards over equivalent future rewards. A major research goal is to identify the factors that influence the temporal discounting rate, so that policy makers could develop interventions to correct for imbalance. It has been shown that a negative change in life circumstances, such as loss of income, is associated with an increase in temporal discounting. Interestingly, negative affect is also associated with increased temporal discounting. Here, we test whether both negative income shock and negative affect lead to greater temporal discounting, and whether they do so independently. We tested 1,145 individuals as the market was crashing in late March 2020 and unemployment rising due to the COVID-19 crisis and then retested 200 individuals as the market was recovering in June 2020. We found that income shock was strongly related to an increase in delay discounting using cross-sectional and longitudinal data. Importantly, this relationship was independent of the negative impact on affect. These findings suggest that the link between income change and delay discounting is a direct result of liquidity constraints, not of changes in affect. This independence may be adaptive, as affect is a noisy reflection of environmental constraints, which may introduce noise to the decision problem leading to suboptimal choice.