Testing the process model of self-control: real time inhibitory control, fatigue and high-calorie snacking

Abstract

Background: Self-control has long been viewed as a limited resource that becomes depleted with use. However, resource models of self-control (e.g. ego depletion) have notable limitations and a recent model of self-control, the Process Model) suggests failures of willpower should be considered shifts in motivational state from effortful to more gratifying pursuits. In the Process Model, fatigue is considered an emotion signalling the opportunity cost of continuing to exert self-control and triggering a motivational shift to more rewarding behaviours. If this is the case, fatigue should be associated with cognitive control and should predict lapses in effortful self-control. The present study tests these predictions. Methods: 65 adults (15M, 50F, M age=38.9 years) completed real-time self-report ratings of fatigue and consumption of high-calorie snack foods, and completed a GoNoGo task (to measure cognitive control) every waking hour over 7 consecutive days using a wrist-mounted electronic diary (ProDiary). Data were analysed using multi-level modelling (observations nested within individuals). Results: GoNoGo performance and fatigue were strongly negatively related (p < .001) but showed different patterns over time. While slow reaction times on the GoNoGo task (indicative of weak cognitive control) were associated with increases in self-reported intake of high calorie snack foods (p<.05), increases in fatigue were not (ns). Conclusions: The results of the present study do not support the assertion of the Process Model that fatigue triggers a motivational shift towards more gratifying behaviour. Fatigue was however, strongly related to cognitive control, an important predictor of health relevant behaviour.