Self-control training and aggressive behaviour

In a validity study of the Taylor paradigm, Giancola and Parrott (2008) demonstrated that direct aggression during the TCRT task were mostly associated with trait physical aggression (assessed using Buss & Perry’s AQ, 1992). Results in Study 1 revealed the influence of trait mindfulness on self-reported aggression, physical aggression, anger, and hostility was mediated by trait self-control. After the inclusion of trait self-control, however, the predicting role of trait mindfulness on physical aggression was no longer significant). It is particularly crucial, therefore, to determine whether the effect of state induced mindfulness on aggressive behaviour could indeed be separated from the effect of self-control. The next aim of the current study is to test whether (i) increasing self-control strength reduces aggressive behaviour in the same way it could be reduced by mindfulness induction, and (ii) the potential reduction of aggressive behaviour due to increases in self- control strength could be strenghtened by mindfulness induction.

As introduced in Chapter 1 (section 1.2.3.2), the majority of self-control experiments appear to fall under the strength model of self-control advocated by Baumeister and colleagues (see Hagger et al.’s meta-analysis, 2010). Here, different acts of self- control are proposed to draw from a common, general “resource” (Baumeister, Vohs, et al., 2007). Performing self-control acts may temporarily deplete this resource (this phenomenon will be investigated in the subsequent studies of this thesis). Conversely, regular practice of self-control over extended periods can

improve the general capacity for self-control.

Outside the area of aggression, the effects of various self-control training (e.g., improving posture, tracking eating habit, using nondominant hand in a mundane

task, avoiding colloquialisms/cursing) is usually demonstrated in the form of increases in stamina or a greater resistance to ego-depletion (e.g., Muraven et al., 1999; Gailliot et al., 2007; Oaten & Cheng, 2006a, 2006b, 2007). That is, individuals’ performance on a self-control task following ego-depleting task is measured twice, at baseline level and after a period of training in a typically unrelated self-control task. The effect of self-control training is assessed by comparing the degree of impairment in self-control performance following depletion between self-control trained and non trained individuals at both time points (see Baumeister et al.’s, 2006, review). More recently, Muraven (2010) found that individuals who practiced self-control (i.e., avoiding sweets or squeezing a handgrip) for two weeks showed significant

improvement in self-control performance (i.e., a stop signal task) compared to those

who practiced tasks that did not require self-control (i.e., solving math problems or keeping a diary of any self-control acts they engaged in). Thus consistent with the ways that muscular strength can be improved, increases in self-control strength could also occur in terms of self-control power. The current study employs self- control training of regulating posture for a period of two weeks (Muraven et al., 1999), and examines the effect of this training on self-control power in a handgrip task. We expect that self-control training participants would show a better handgrip power compared to non training participants.

Importantly, the effect of self-control training is also tested on aggressive behaviour. Corresponding with the view that self-control serves to restrain aggressive impulses (see Denson et al., 2012; DeWall et al., 2011), training in self-control has been shown to decrease aggression, particularly following provocation. Denson et al. (2011) found that a two-week training in physical regulation (using nondominant hand in mundane tasks) reduced direct aggression in the TCRT task (i.e., the mean score of blast intensity and duration) in response to insulting feedback from a bogus opponent, but only amongst individuals who scored higher in trait physical aggression (for details see section 1.2.3.3, Chapter 1). The same physical training, and a verbal regulation training of avoiding colloquialisms were used in Finkel et al.’s (2009) study involving a hypothetical scenario of provocations from an intimate partner. Specifically, all participants were asked to perform an ego-depleting task

(i.e., attention control task) before they completed a self-reported measure of violent inclinations towards a provoking partner—at baseline level and after performing self-control training. As predicted, self-control trained participants showed less violent inclination over time whereas no reductions were found in non self-control trained participants.

As mentioned in the earlier section, the current study adds a no-provocation condition, thus the impact of self-control training can be measured on both provoked and unprovoked aggression. In addition, self-control training is expected to influence other dependent measures, i.e., the maximum blast latency, rating of indirect aggression, and self-control performance in the same way these measures are proposed to be influenced by mindfulness induction. Moreover, we expect that mindfulness induction could strengthen the effect of self-control training on aggressive behaviour and self-control performance.

Since Study 1 found that trait mindfulness and self-control reduced individuals’ tendency to harm themselves in a similar way as they predicted measures of trait aggression (section 2.4.8 and 2.4.9 in Chapter 2), the impact of mindfulness induction and self-control training could also be influenced by self-harm status. The impact of these manipulations may also be affected by individual differences in sensitivity to provocations (SP) and frustrations (SF). In the adapted TCRT task, individual differences in SP has been shown to be positively related to blast intensity following provoked aggression and to the maximum blast latency, but not to indirect aggression (Lawrence & Hutchinson, 20013b). Thus measures of individual differences in mindfulness, self-control, aggression, SP, SF, and self-harm are also assessed in the current study, along with relevant demographic factors, i.e., sex, race/ethnicity, and participants’ current practice of mindfulness.

3.2 HYPOTHESES

The primary hypotheses of this study are concerned with the role of mindfulness induction and self-control training on aggressive behaviour, and predict that:

1. Compared to those not receiving mindfulness induction, participants receiving mindfulness induction will:

a. Deliver lower levels of blast intensity to the opponent, particularly on low provocation trials. No strong prediction is made regarding the levels of blasts delivered under no provocation or high provocation trials.

b. Wait longer before delivering the maximum blasts to the opponent. c. Deliver lower ratings of anonymous reputation damage to the opponent. 2. Those who receive self-control training will be less aggressive than those without

self-control training, thus mirroring the associations with mindfulness induction (Hypothesis 2a – 2c).

3. Mindfulness induction will strengthen the effect of self-control training on aggressive behaviour. Specifically, compared to self-control training participants with no mindfulness induction, self-control training participants who also receive mindfulness induction will:

a. Deliver lower levels of blast intensity to the opponent, particularly on low provocation trials. No strong prediction is made under no provocation or high provocation trials.

b. Wait longer before delivering the maximum blasts to the opponent. c. Deliver lower ratings of anonymous reputation damage to the opponent. 4. The moderation of mindfulness on the link between self-control training and

aggressive behaviour will persist after accounting for the potential influence of individual differences in mindfulness, self-control, aggression (i.e., trait aggression, sensitivity to provocations [SP] and frustrations [SF]), sex, self-harm, ethnicity/culture, and current mindfulness practice.

In addition, we predict that:

5. Mindfulness induction will strengthen the effect of self-control training on self- control performance, as measured by handgrip power after accounting for trait and demographic covariates.

As a whole, we hypothesise that self-control training and mindfulness induction will predict lower levels of aggression and a better self-control (handgrip) performance, after accounting for covariates (personality variables). Moreover, mindfulness induction will strengthen the effect of self-control training on aggression.

3.3 METHODS

3.3.1 Participants

University of Nottingham students took part in two times points of the current study. A total of 147 (72 females) students entered Time 1 of the study. Based on sex, participants were randomly assigned to one of four groups (see randomisation details in the next section). Data were removed from further analyses due to: not attending the Time 2 session (n = 19 from the self-control training condition and n = 18 from the no training condition), not providing any compliance scores to the self- control training (4 participants), and expressing spontaneous suspicions regarding the TCRT task (7 participants). Our final sample consisted of 99 participants (51 females). Participants’ mean age was 20.02 (SD = 2.66). The ethnic distribution was 61.6% White, 29.3% Asian, 7.1% participants rated themselves as “Others”, and 2.0% did not report their ethnical background. Concerning current mindfulness practice, 91.9% participants reported never having encountered mindfulness, 3.0% practised them on a monthly basis, 4.0% on weekly basis, and 1% (1 participant) practised them on daily basis. The experiment lasted from October until November 2011.

3.3.2 Design

To these ends, we conducted a 2 (self-control training vs. no self-control training) x 2 (mindfulness induction vs. relaxation) experimental design (See Figure 3.1 for the flow of participants). Stratified sampling technique was employed to assess the effect of sex, as sex differences in aggression are prevalent in studies using the TCRT tasks (e.g., Anderson et al., 2008; Giancola & Parrott, 2008).

Figure 3.1. Flow of participants through Study 2.

Note. M = Males; F = Females