Abstract
Self-control failure has enormous personal and societal consequences. One of the most debated models explaining why self-control breaks down is the Strength Model, according to which self-control depends on a limited resource. Either previous acts of self-control or taking part in highly demanding cognitive tasks have been shown to reduce self-control, possibly due to a reduction in blood glucose levels. However, several studies yielded negative findings, and recent meta-analyses questioned the robustness of the depletion effect in humans. We investigated, for the first time, whether the Strength Model applies to a non-human primate species, the tufted capuchin monkey. We tested five capuchins in a self-control task (the Accumulation task) in which food items were accumulated within individual’s reach for as long as the subject refrained from taking them. We evaluated whether capuchins’ performance decreases: (i) when tested before receiving their daily meal rather than after consuming it (Energy Depletion Experiment), and (ii) after being tested in two tasks with different levels of cognitive complexity (Cognitive Depletion Experiment). We also tested, in both experiments, how implementing self-control in each trial of the Accumulation task affected this capacity within each session and/or across consecutive sessions. Repeated acts of self-control in each trial of the Accumulation task progressively reduced this capacity within each session, as predicted by the Strength Model. However, neither experiencing a reduction in energy level nor taking part in a highly demanding cognitive task decreased performance in the subsequent Accumulation task. Thus, whereas capuchins seem to be vulnerable to within-session depletion effects, to other extents our findings are in line with the growing body of studies that failed to find a depletion effect in humans. Methodological issues potentially affecting the lack of depletion effects in capuchins are discussed.
Highlights
Self-control can be defined as the ability to inhibit a dominant response in order to achieve a future goal (Mischel, 1974; Tangney et al, 2004; Osvath and Osvath, 2008), and is considered an important key to success in life for both human and non-human animals
It has been observed that taking part in highly demanding cognitive tasks, such as the switching arithmetic task may decrease performance in a subsequent self-control task (Kiesel et al, 2010; Schneider and Anderson, 2010; Barutchu et al, 2013)
We evaluated how implementing self-control in each trial of the Accumulation task affected this capacity within each session and/or across consecutive sessions
Summary
Self-control can be defined as the ability to inhibit a dominant response in order to achieve a future goal (Mischel, 1974; Tangney et al, 2004; Osvath and Osvath, 2008), and is considered an important key to success in life for both human and non-human animals. One of the most debated models is the Strength Model (Baumeister, 2002), according to which all acts of self-control deplete a limited resource causing short-term impairments in subsequent acts of self-control. Participants were initially asked to exert either a high level or a relatively low level of self-control, and had to complete a different task in which self-control was required. In the first experiment of Muraven et al (1998), participants required to suppress or amplify their emotions while watching a sad movie, subsequently showed less persistence in squeezing a handgrip than participants who had not been required to regulate their emotions while watching the movie. The above findings support the hypothesis of selfcontrol as a limited resource that can become temporarily depleted
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