The profound insights put forward by Norenzayan et al. about the societal impact of prosocial religion mesh well with the theoretical framework that has informed much of our own work. In particular, Baumeister (Reference Baumeister2005) reviewed extensive psychological research on human processes and dispositions, leading to the speculative conclusion that the distinctively human traits are largely adaptations designed to facilitate culture. In this brief comment, we focus on one of these traits – namely, the advanced, flexible, and relatively powerful form of self-control seen among humans.

The great social leap forward seen among humankind, as compared with other primates, is the extensive involvement in social interactions and relationships with non-kin, so that they could have mutually beneficial interactions with distant acquaintances and even strangers. These have extended beyond one-to-one interactions to include participation in much larger social networks and systems, such as marketplaces, governments, and armies.

Whereas cooperation with close relatives may come naturally, on the basis of shared genes, cooperating with non-kin and strangers is more difficult. Moral rules point the way toward making these interactions possible. Economic marketplaces, for example, can provide benefits to all who participate, but they only work if people maintain some respect for honest disclosure, fair trade, property rights, and the like. Widening the circle of trust, so that people can treat non-kin fairly, is always an incomplete transition (Fukuyama Reference Fukuyama2011). Even in modern societies, people tend to trust and cooperate with kin more than strangers, especially during times of societal instability.

Self-control enables people to override impulses and obey abstract rules. The point of our comment is that prosocial religions may have contributed to cultural progress partly by improving self-control. Evidence linking religiosity to self-control was reviewed by McCullough and Willoughby (Reference McCullough and Willoughby2009), though their work was motivated by seeking to explain the link between religion and longevity, not morality. Moreover, many findings were correlational, rendering ambiguous what caused what. The link between self-control and moral behavior has clear support (e.g., Baumeister & Exline Reference Baumeister and Exline1999), such as reflected in experimental evidence that people perform immoral actions more when their self-control is impaired than when fully functioning (Mead et al. Reference Mead, Baumeister, Gino, Schweitzer and Ariely2009).

Self-control can fail for several reasons, reflecting its structural and motivational bases (Baumeister & Heatherton Reference Baumeister and Heatherton1996). Specifically, it can fail because of unclear standards, insufficient monitoring, depletion of regulatory resources, and a heightened emphasis on immediate desires rather than long-term enlightened self-interest. We suggest that religion can help reduce each of those pitfalls.

Successful self-control is facilitated by having clear and consistent standards. One may also assume that successful cooperation is facilitated when individuals endorse the same standards. As Norenzayan et al. note, all-encompassing prosocial gods helped this process by advocating single sets of moral rules that all people were expected to obey. Indeed, Jaynes (Reference Jaynes1976) proposed that conflicting demands from multiple gods were a factor leading to a preference for monotheism and a heightened sense of conscious moral responsibility. Even today, religiosity is linked to relatively low levels of goal conflict (Emmons et al. Reference Emmons, Cheung and Tehrani1998).

Monitoring (keeping track of relevant behaviors) is also vital for effective self-regulation. Here again, religion helped. Whereas the early multiple gods were often preoccupied with their own adventures, the large prosocial gods came to be understood as constantly watching people, particularly for virtuous and immoral actions. Being watched makes one self-conscious, and so belief in a watchful god likely made people aware of themselves. Secret actions thus ceased to be secret, rendering morality a ubiquitous concern. Self-awareness inherently seems to involve comparison of self to standards (Duval & Wicklund Reference Duval and Wicklund1972), and so the process of moral self-evaluation was likely increased by belief in a god with a clear and consistent set of moral rules.

Self-regulation can also fail because the capacity for altering one's responses is temporarily diminished. Ego depletion is a state of diminished willpower. Although causal evidence is lacking, it seems plausible that religion could help in two ways. First, ego depletion typically reflects efforts to conserve a partly depleted resource, and people can self-regulate despite depletion when sufficiently motivated (e.g., Muraven & Slessareva Reference Muraven and Slessareva2003). An omnipresent, judgmental god could well help supply such motivation. Second, regular exercise of self-control appears to strengthen one's capacity for self-control (e.g., Baumeister et al. Reference Baumeister, Gailliot, DeWall and Oaten2006). As suggested by McCullough and Willoughby (Reference McCullough and Willoughby2009) and others, regular participation in church practices, from rituals to prayer to meditation, may serve as self-control exercises that would strengthen the capacity. Desmond et al. (Reference Desmond, Ulmer and Bader2013) found that frequency of prayer and religious attendance correlated positively with adolescents’ self-control, even after controlling for relevant demographic variables. That could indicate the strengthening benefit of religious activity, though other explanations could be proposed.

Last, self-regulation fails when aversive emotional states prompt people to seek immediate pleasure and benefit rather than do what is best in the long run (e.g., Tice et al. Reference Tice, Bratslavsky and Baumeister2001). Again, religion can help in multiple ways. Invoking eternity is likely helpful in maintaining a long-term focus, as is the assurance of intense future punishments for current lapses. Religion may function similarly to these tactics by promoting a long-range time perspective (e.g., consequences in an afterlife) and increasing the salience of long-term goals (Baumeister et al. Reference Baumeister, Bauer and Lloyd2010). Highly intrinsically religious Turkish Muslims, to take one example, have more future-oriented thinking than do less religious Muslims (Öner-Özkan Reference Öner-Özkan2007). Religion also helps mitigate current suffering by helping individuals place it in long-range contexts, thereby possibly reducing the need to seek solace through illicit pleasures (Baumeister Reference Baumeister1991).

The advent of large-scale, morally prescriptive gods was a major step in the evolution of large societies, as Norenzayan et al. argue. We propose that the beneficial effects of religion on self-control and, through that mechanism, on morality, were one vital part of this process.