Is Increased Reward Responsivity Responsible for the After-Effects of Self-control? An EEG Approach.

Resource Model of Self-Control
Self-control has been extensively studied through the lens of the resource model. According to this model, the capacity to override or alter one's responses depends on a limited inner resource or strength [1,2]. Acts of self-control are thought to consume or deplete this strength, resulting in a temporary decline in the capacity for self-control (i.e., ego depletion). In support of this view, numerous studies have found that engaging in a taxing (or depleting) self-control task temporarily undermines performance on subsequent demanding tasks [2]. Nevertheless, empirical controversies related to the validity of the resource model have arisen. An initial meta-analysis of the resource model obtained evidence for consistent, large effects [3], but more recent meta-analyses concluded that the effect is negligible after adjusting for publication bias [4,5]. However, methods used in these latter meta-analyses have, in turn, been called into question [6]. Finally, a multi-laboratory experiment found non-significant aftereffects of self-control exertion [7], whereas other preregistered, large-sample studies reported
statistically significant, albeit smaller than expected, effects [8,9]. Collectively, these works suggest that the validity of the resource model of self-control and the aftereffects of self-control remain poorly understood.
Reward Responsivity Hypothesis of Self-Control
Kelley et al. [10] recently proposed a reward responsivity hypothesis of self-control. This hypothesis states that, irrespective of self-control success, the act of exercising self-control is aversive and engenders negative affect [11]; and in order to countermand this discomfort, reward-seeking behaviour
may be amplified after bouts of self-control, to bring individuals back to a mildly positive baseline state. Several studies have found evidence that exercising self-control increases subsequent reward-seeking behaviour, including eating, spending, and sexual behaviour [2]. Indeed, these behavioural outcomes
could be due to a reduction in the capacity for control (as others initially assumed) or due to increases in reward responsivity and approach motivation [10]. Besides, several studies, in line with the hypothesis, have circumvented this interpretational ambiguity by having participants' complete reward-related tasks
requiring little to no self-control. These studies find that self-control exertion enhances self-reported approach motivation [12] and positive emotional reactivity [13]. Several theoretical models of self-control are also consistent with the reward responsivity hypothesis. The process model proposes that shifts in motivation and attention steer individuals away from the further engagement of control and toward rewards [14,15]. Integrative self-control theory posits that, because control efforts are taxing and dependent upon finite resources, exercising self-control eventually tips the scales toward greater desire-driven reward-seeking behaviour [16]. Value-based choice models of selfcontrol suggest that exercising self-control shifts valued-based calculations in favour of more immediate, hedonic options over more effortful options in accord with one's long-term goals [17]. Similarly, both cognitive dissonance [18,19] and psychological contrast [20] accounts of effort suggest that aversive states elicited by the exertion of effort make the end-result or reward appear more valuable.
Furthermore, research on counter-regulation indicates that individuals more easily process information that is incongruent with their prevailing emotional state [21]. Insofar as exercising self-control is aversive, counter-regulation would predict greater ease in processing reward-relevant information, leading to a compensatory attentional shift towards rewards after exerting self-control. Finally, opponent process theories of motivation assume that organisms have a fundamental motivatation to maintain homeostasis and shifts