Strength model of self-control

Given that research on self-control has focused on people’s effort to stimulate desirable responses and inhibit undesirable responses, it is not surprising that body of evidence has linked good self-control to a variety of benefits. Amongst these benefits include healthier interpersonal relationship, greater popularity, better mental health, effective coping skills, superior academic performance, as well as less vulnerability to drug and alcohol abuse, aggression, criminality, and eating disorders (see de Ridder, Lensvelt-Mulders, Finkenauer, Stok, & Baumeister, 2012; Moffitt et al., 2011). However, exerting self-control is not without cost.

In considering the costs of self-control, it is relevant to differentiate between its trait and state aspects. Trait self-control is a broad, dispositional tendency to exert self- control; the state is a current propensity to exert self-control. While trait self-control appears to be a highly desirable quality, the momentary act of self-control seems to require significant sacrifices (for an overview, see Baumeister & Alquist, 2009). According to Baumeister et al. (1994), much like a muscle, the capacity of the self to change itself relies on the availability of a common and limited pool of self-control “resources”, or self-control strength. The construct of self-control strength corresponds to the “Operate” phase in the TOTE theory (Bauen & Baumeister, 2011; Baumeister, Schmeichel, et al., 2007), when a person has detected a discrepancy between the desired and current states, and is prepared to initiate actions to eliminate or reduce the discrepancy. At this point, one must have sufficient inner resources to alter its own responses. Because the common resource for self-control is limited, after exerting initial self-controlled regulation, the capacity for further control is decreased. This temporary deficit is known as ego-depletion.

Early evidence for ego-depletion was reported from Baumeister and colleagues laboratory (i.e., Muraven, Tice, & Baumeister, 1998; Baumeister, Bratslavsky, Muraven, & Tice, 1998). In one study, individuals who were required to regulate emotions while watching an upsetting video performed less well on subsequent handgrip stamina. In their other study, when participants were required to suppress thoughts about a white bear, they subsequently more quickly gave up on an

unsolvable anagram. In these studies, controlling aspects of the self that are normally spontaneous and impulsive, such as expressing emotions or the innate tendency to recall thoughts of a suggested object (the so-called cognitive rebound phenomenon) requires effortful self-control and draws from a reservoir of self- control resources. In doing so, it is argued that the resource is depleted, leaving less available resources to exert self-control on subsequent self-control tasks.

Following Baumeister and colleagues’ initial tests, studies have replicated the ego- depletion effect extensively. Various spheres of self-control have been employed in laboratory settings, including controlling attention, controlling emotions, controlling impulses, controlling thoughts, cognitive processing, choice and volition, and social processing (Baumeister, Vohs, et al., 2007). Supporting the strength model proposal on a common resource of self-control, Hagger, Wood, Stiff, and Chatzisarantis’s (2010) meta-analysis found a robust effect of depletion on performance on self- control task, with minimal variation across spheres of self-control.

While performing self-control acts may temporarily deplete the self-control resources, repeated practice of self-control over a period of time may enlarge or strengthen these resources. This effect has been shown particularly in the form of a less susceptibility to depletion. For instance, in Muraven, Baumeister, and Tice’s (1999) study, participants’ self-control performance was measured using a task of overriding physical discomfort (a handgrip task), given before and after an ego- depleting task (suppressing thoughts of a white bear) prior to a self-control training of tracking eating habits or regulating posture for two weeks, and following self- control training. As expected, following the self-control training, participants displayed better handgrip performance after the thoughts suppression task, as opposed to their pre-training handgrip performance.

Likewise, people’s ability to regulate their use of stereotypes improved following two weeks of self-control training of using the nondominant hand or avoiding colloquialisms/cursing (Gailliot, Plant, Butz, & Baumeister, 2007). In a series of studies, Oaten and Cheng also showed that people’s ability on the visual tracking task increased after they were trained over a period of months in formal academic

study (2006a), physical exercise (2006b), and financial monitoring (2007). Crucially, Muraven (2010) demonstrated that effect of self-control training on self-control performance following depletion cannot be explained by alternative mechanisms such as self-awareness (i.e., monitoring one’s self-control activities with no specific attempt to practice self-control), self-fulfilling prophecies, or self-efficacy.

In short, the existing research appears to establish a direct relationship between self- control and ego-depletion such that greater exertion of self-control leads to more depletion. Until the resource for self-control can be replenished, one’s ability to perform further self-control acts is compromised. Several counteracting variables for the depletion effect on self-control performance have been identified, such as glucose, humour, laughter, cash incentives, implementation intentions, and social goals (see Baumeister, Vohs, et al., 2007), and more recently, mindfulness (Friese, Messner, & Schaffner, 2012). Just as a muscle that gets stronger through exercise, a longer term effect of self-control practice also promotes a greater resistance to depletion (see Baumeister, Gailliot, DeWall, & Oaten, 2006).