Christian Wiesner

Self-control enables people to override momentary thoughts, emotions, or impulses in order to pursue long-term goals. Good self-control is a predictor for health, success, and subjective well-being, as bad self-control is for the opposite. Therefore, the question arises why evolution has not endowed us with perfect self-control. In this article, we draw some attention to the hidden benefits of self-control failure and present a new experimental paradigm that captures both costs and benefits of self-control failure. In an experiment, participants worked on three consecutive tasks: 1) In a transcription task, we manipulated how much effortful self-control two groups of participants had to exert. 2) In a number-comparison task, participants of both groups were asked to compare numbers and ignore distracting neutral versus reward-related pictures. 3) After a pause for recreation, participants were confronted with an unannounced recognition task measuring whether they had incidentally encoded the distracting pictures during the previous number-comparison task. The results showed that participants who exerted a high amount of effortful self-control during the first task shifted their priorities and attention toward the distractors during the second self-control demanding task: The cost of self-control failure was reflected in worse performance in the number-comparison task. Moreover, the group which had exerted a high amount of self-control during the first task and showed self-control failure during the second task was better in the unannounced third task. The benefit of self-control failure during number comparison was reflected in better performance during the recognition task. However, costs and benefits were not specific for reward-related distractors but also occurred with neutral pictures. We propose that the hidden benefit of self-control failure lies in the exploration of distractors present during goal pursuit [...]

Sleep helps to protect and renew hippocampus-dependent declarative learning. Less is known about forms of learning that mainly engage the dopaminergic reward system. Animal studies showed that exogenous melatonin modulates the responses of the dopaminergic reward system and acts as a neuroprotectant promoting memory. In humans, melatonin is mainly secreted in darkness during evening hours supporting sleep. In this study, we investigate the effects of a short period of daytime sleep (nap) and endogenous melatonin on reward learning. Twenty-seven healthy, adult students took part in an experiment, either taking a 90-min afternoon nap or watching videos (within-subject design). Before and after the sleep vs. wake interval, saliva melatonin levels and reward learning were measured, and in the nap condition, a polysomnogram was obtained. Reward learning was assessed using a two-alternative probabilistic reinforcement-learning task. Sleep itself and subjective arousal or valence had no significant effects on reward learning. However, this study showed for the first time that an afternoon nap can elicit a small but significant melatonin response in about 41% of the participants and that the magnitude of the melatonin response predicts subsequent reward learning. Only in melatonin responders did a short nap improve reward learning. The difference between melatonin-responders and non-responders occurred very early during learning indicating that melatonin might have improved working memory rather than reward learning. Future studies should use paradigms differentiating working memory and reward learning to clarify which aspect of human feedback learning might profit from melatonin.