Researchers have investigated the influence of exercising self-control on an individual’s convergent and divergent thinking, discovering that participants demonstrate poor convergent thinking after exercising self-control (Baumeister et al., 1998; Schmeichel et al., 2003). However, Chiu (2014) and Chiu et al. (2017) observed that after exercising self-control, participants demonstrated improved divergent thinking, indicating that exercising self-control resulted in contrasting effects on convergent and divergent thinking.

    Although studies have indicated that exercising self-control reduced convergent thinking performance, they have also found that exercising self-control enhanced divergent thinking performance. However, the effects of the interaction between exercising self-control (e.g., active self-control) and trait self-control (TSC) and convergent–divergent thinking have yet to be investigated. In one study, convergent and divergent thinking performance were negatively correlated (r = -.54; Chiu, 2010), and hence, we would expect different moderating effects on convergent and divergent thinking when participants with high or low TSC exercise self-control. Therefore, this study investigated the effects of the interaction between exercising self-control and TSC on convergent and divergent thinking.

    TSC can be defined as general and cross-domain self-control capacity (Imhoff et al., 2014), which includes the regulation of thoughts, emotions, impulses, and performance (Baumeister et al., 1994). TSC is a personality trait, thus distinguishing it from the state of exercising self-control. In researching how the interaction between TSC and the state of self-control (i.e., exercising self-control) influence subsequent thinking performance, some researchers have proposed that high-TSC participants should be less vulnerable to self-control depletion because they have relatively more mental resources to draw from and can avoid reaching the point of depletion (e.g., Dvorak & Simons, 2009).

    Imhoff et al. (2014), however, suggested that in contrast to low-TSC participants, high-TSC participants consumed more candies after manipulations were applied to deplete their self-control. DeWall et al. (2007), by contrast, determined that compared with low-TSC participants, high-TSC participants rarely inhibit their impulses actively and therefore less frequently engage in the effortful inhibition of impulses. The active suppression of desires in everyday life enables individuals to develop increased resistance to temptations (Baumeister et al., 1998; Gailliot et al., 2007), but high-TSC individuals typically avoid tempting situations in everyday life, and consequently, actively resisting temptation becomes increasingly difficult for them. When forced to exercise self-control against temptations, high-TSC individuals tend to show a comparatively weak ability.

    The preceding discussion demonstrates that it is necessary to clarify how exercising self-control interacts with TSC and then affects convergent and divergent thinking. Therefore, this study investigated the influences of the interaction of exercising self-control and TSC on convergent and divergent thinking. In Study 1, 92 participants were randomly assigned to either the exercising self-control condition or the control condition. Under the exercising self-control condition, participants were prohibited from using Chinese characters containing the radicals “ イ” or “ 口” while writing. Next, they were asked to complete a critical thinking test (i.e., to test convergent thinking). The results showed that exercising self-control did not reduce convergent thinking, and participants with low TSC demonstrated higher performance in critical thinking under the exercising self-control condition than did participants with high TSC. However, under the control condition, both low- and high-TSC participants exhibited similar levels of critical thinking. Study 2 enrolled 77 participants. Except for the dependent variable, which was changed to divergent thinking, the procedures of Study 2 were identical to those of Study 1. The results indicated that participants with high TSC demonstrated superior originality under the exercising self-control condition to the participants with low TSC. However, under the control condition, both the low- and high-TSC participants exhibited similar levels of originality. These findings suggest that TSC moderates the effects of exercising self-control on convergent and divergent thinking.

    Participants with low TSC significantly improved their performance in convergent thinking after exercising self-control. However, participants with high TSC performed significantly better than did those with low TSC in terms of the originality of divergent thinking after exercising self-control. In regard to the moderating effect of TSC on the association between exercising self-control and convergent thinking, we found that participants with low TSC improved their convergent thinking performance after exercising self-control. This finding accords with the negative effect found by Imhoff et al. (2014) rather than the proposition that high TSC would have a positive effect in the exercising self-control condition. In terms of the positive effects of high TSC, we proposed that the convergent thinking of participants with high TSC would not be affected by TSC after exercising self-control and that due to the negative effect of high TSC (Imhoff et al., 2014), the participants with high TSC would exhibit significantly lower performance on convergent thinking after exercising self-control. However, in this study, the participants with low TSC exhibited a significant increase in convergent thinking performance after exercising self-control. Additionally, the participants with high TSC demonstrated lower performance in convergent thinking after exercising self-control compared with the control group. Thus, under the exercising self-control condition, the results tended to support the negative effect of high TSC on convergent thinking.

    Exercising self-control had a significant effect on the participants’ performance in fluency, flexibility, and originality; however, the interaction between exercising self-control and TSC was found to only influence originality. In addition, it was mainly the participants with high TSC who exhibited increased originality after exercising self-control, whereas participants with low TSC were not affected. Moreover, the interaction between exercising self-control and TSC did not affect the number of ideas produced or the variability of ideas produced. However, it did influence the novelty of ideas and encouraged more distant associations (Mednick, 1962). This might be because participants with TSC had reduced self-control inhibition after exercising self-control (Schmeichel et al., 2010), making them more receptive to novel and more distant ideas, thereby increasing only originality but not fluency (more ideas) or variability (more types of ideas). This accords with previous research indicating that participants with higher inhibition demonstrated lower creativity (Carson et al., 2003).

    In summary, under the exercising self-control condition, the negative effect of TSC on convergent thinking was clearly supported; therefore, this study’s findings are consistent with those of Imhoff et al. (2014). However, the positive effect of TSC (DeWall et al., 2007; Gailliot et al., 2006) was not supported. Notably, the results of this study indicated that while both the participants with high and low TSC exercised self-control, those with high TSC demonstrated increased originality but decreased convergent thinking. These results indicated that whether exercising self-control affects convergent or divergent thinking depends on the level of TSC; moreover, compared with people with low TSC, people with high TSC exhibited lower convergent thinking and higher divergent thinking after exercising self-control. Hence, high TSC was associated with a negative effect on convergent thinking and a positive effect on the originality of divergent thinking after exercising self-control.