An experimental analysis of acquired impulse control among adult humans intolerant to alcohol Jianxin Wanga, Yulei Raoa, and Daniel E. Houserb,c,1 aSchool of Business, Central South University, Changsha 410083, People’s Republic of China; bDepartment of Economics, George Mason University, Fairfax, VA 22030; and cInterdisciplinary Center for Economic Science, George Mason University, Fairfax, VA 22030 Edited by Roy Baumeister, Florida State University, Tallahassee, FL, and accepted by Editorial Board Member Michael S. Gazzaniga December 22, 2016 (received for review July 9, 2016) The ability to control tempting impulses impacts health, education, leads to systematic differences in the need to practice small acts and general socioeconomic outcomes among people at all ages. of self-control. This paper fills that gap. Consequently, whether and how impulse control develops in adult Our interest is to investigate a key prediction of the strength populations is a topic of enduring interest. Although past research model: repeatedly practicing small acts of self-control leaves a has shed important light on this question using controlled in- person more able to use willpower than another observationally tervention studies, here we take advantage of a natural experiment identical person without this practice. Many experimental tests of in China, where males but not females encounter substantial social this prediction have appeared (17, 18). A typical experiment assigns pressure to consume alcohol. One-third of our sample, all of whom people randomly to practice self-control (or not) for a relatively are Han Chinese, is intolerant to alcohol, whereas the remaining short period (usually days or weeks), and subsequently assesses control sample is observationally identical but alcohol tolerant. their ability to use self-control in a laboratory task. The meta- Consistent with previous literature, we find that intolerant males analysis of Hagger et al. (17) reveals that the strength model is are significantly more likely to exercise willpower to limit their generally supported by the literature, and in particular the ability to alcohol consumption than alcohol-tolerant males. In view of the practice self-control does seem to increase as a result of practice. strength model of self-control, we hypothesize that this enables [Others who have analyzed these data using different approaches improved impulse control in other contexts as well. To investigate SCIENCES reach different conclusions (19).] Baumeister and Vohs (18) fur- ECONOMIC this hypothesis, we compare decisions in laboratory games of self- ther argue that, “exercising self-regulation of one or two sorts of control between the tolerant and intolerant groups. We find that behaviors causes discernible improvements on seemingly unrelated males intolerant to alcohol and who regularly encounter drinking tasks.” At the same time, as noted by Muraven (20), this literature environments control their selfish impulses significantly better than suffers from confounds that create difficulties in tracing the source their tolerant counterparts. On the other hand, we find that female of this effect to an increase in the effective stock of willpower. Han Chinese intolerant to alcohol do not use self-control to limit ’ alcohol consumption more than tolerant females, nor do the tolerant For example, one reason a person s self-control might improve and intolerant females exhibit differences in self-control behaviors. after an intervention is because they become more aware of the Our research indicates that impulse control can be developed in adult importance of self-control. In the same way that raising the sa- populations as a result of self-control behaviors in natural environ- lience of a norm tends to improve obedience to that norm (21), ments, and shows that this skill has generalizable benefits across emphasizing the importance of self-control by asking people to behavioral domains. practice self-control may leave them more likely to comply with tasks that require self-control. Muraven (20) suggests that another self-control | strength model | alcohol intolerance | cheating | confound is that a person, focused on and thus realizing they are natural experiment able to practice self-control, may gain additional confidence in this umans are often tempted to pursue an immediate benefit, Significance Heven when they know it may result in substantial long-run cost. Controlling these tempting impulses requires willpower (1). Impulse We find that alcohol intolerance, which occurs randomly and control is important to a large number of social and economic en- leads affected people systematically to resist the impulse to vironments, including health behavior (2) and weight loss (through consume alcohol, enables improved impulse control in another both food control and exercise) (3), violence and crime (4), and behavioral domain. Our findings show that impulse control can develop in adult populations as a result of exercising routine spending and saving in household finances (5). A long multidisci- behaviors in naturally occurring environments. This finding is plinary empirical and theoretical literature discusses the role of important because the ability to control tempting impulses sig- impulse control in social and economic decision making (6, 7). nificantly impacts the health and well-being of people at all ages. The question of whether impulse control can be acquired or Our findings complement theory by providing rigorous empirical – improved has been long studied, both empirically (8 10) and the- evidence that simple lifestyle changes may have significant per- oretically. An important contribution to this literature is the so- sonal well-being benefits. In particular, small acts of self-control, called “strength model” of self-control (see, for example, refs. such as resisting drinking or always waking at the same time, can 11–13), which argues self-control is like a “muscle” that can be increase one’s overall ability to resist selfish temptations. depleted by short-term exertion, and yet that the same exertion can lead to it strengthening. [Although we focus on the strength model, Author contributions: J.W., Y.R., and D.E.H. designed research; J.W. performed research; J.W. and D.E.H. analyzed data; and J.W., Y.R., and D.E.H. wrote the paper. alternative models of self-control have been suggested (14, 15).] The authors declare no conflict of interest. The model predicts that practicing self-control on specific tasks ’ This article is a PNAS Direct Submission. R.B. is a Guest Editor invited by the Editorial increases one s ability to exercise self-control broadly across mul- Board. tiple domains (16). This prediction has been frequently tested using Freely available online through the PNAS open access option. designed experimental interventions (17, 18). To our knowledge, 1To whom correspondence should be addressed. Email: [email protected]. however, there have been no tests of the strength model based on This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. “natural experiments,” where exogenous population variation 1073/pnas.1610902114/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1610902114 PNAS Early Edition | 1of6 Downloaded by guest on October 1, 2021 ability. This increased confidence may affect their ability to exer- display greater self-control over selfish cheating behavior than cise self-control in a subsequent task, particularly one in which their tolerant counterparts. Furthermore, females do not exhibit their performance is being monitored. differences between tolerant and intolerant groups in either We study impulse control among adult Han Chinese displaying propensity to use self-control in drinking environments or in intolerance to alcohol, in comparison with a control group of adult decisions to cheat. Han Chinese without this intolerance. We provide evidence that These results are consistent with the view that impulse control, male Han Chinese with alcohol intolerance practice small acts of like a muscle, can be developed in natural environments as a self-control over alcohol more regularly than males in our tolerant consequence of practicing small acts of self-control, and that this groups. We argue this is the only systematic difference in the ex- has generalizable benefits across multiple behavioral domains (16, ercise of self-control between the tolerant and intolerant groups. 18, 20). It is worth emphasizing that, whereas substantial experi- Consequently, the alcohol-intolerant male sample would be expec- mental research based on designed interventions has provided ted, by the strength model, to be better able to control tempting support for the strength model (e.g., refs. 13 and 37–39), to our impulses. Note that our approach has the advantage that confounds, knowledge ours is unique in discovering the positive spillover such as salience and confidence-building, are absent. effects associated with practicing self-control in a naturally Our sample (48.6% female) is drawn from the Han Chinese occurring context. undergraduate population at a leading Chinese university. Mem- bers of our sample are similar in age and background: homoge- Literature Review neity of the participant pool is the reason we use this population. Acquired Impulse Control. Impulse control can be acquired We are aware of no evidence that alcohol intolerance is associated through practice. Ainslie (8) used pigeons to study the possibility with personality or preferences,