Related Literature

The relationship between religion and various aspects of social behavior has been studied extensively in the social sciences. One stream of the literature focuses on self-reported religiosity and how this correlates with higher charitable donations, volunteerism and an increased honesty (Sosis & Ruffle, 2003; Trimble, 1997). There also exists evidence that societies belonging to world religions or to religions with a more moralistic, knowledgeable and punishing god are more pro-social than other societies (Henrich et al., 2010; Purzycki et al., 2016). Interestingly, the emergence of moralizing religions increases historically with greater societal size, which may be an indicator of the role of religion as a “controlling device” of governing elites (Roes &

Raymond, 2003). Yet, although insightful to the relationship between religion and social behavior, these studies cannot reveal causal mechanisms. Religiosity may be correlated with unobserved factors that promote pro-sociality or the relationship may be reverse and pro-social dispositions cause people to become religious. Furthermore, self-reported religiosity may be

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biased.³ A second strand of the literature uses experimental priming methods to make subjects subconsciously think about religious beliefs, religious practice or religious belongings. The cumulated evidence supports the non-experimental findings. There seem to be causal effects of religiosity on honesty (Bering, 2006; Mazar, Amir, & Ariely, 2008), generosity (Ahmed & Salas, 2011; Bargh & Chartrand, 1999; Azim F. Shariff & Norenzayan, 2007), and an increase in cooperation (Ahmed & Salas, 2011; Horton, Rand, & Zeckhauser, 2011), which has been confirmed in a recent meta-analysis covering 93 studies of which 25 are on pro-sociality (A. F.

Shariff, Willard, Andersen, & Norenzayan, 2016).

The evidence on pro-sociality and religion has mainly focused on behavior towards religious in-group members (or left the receiver unspecified) which does not allow to investigate religions’ role for conflict. However, there is also ample evidence that religious pro-sociality is uniquely applicable to in-group targets and outgroups are treated less favorably (Blogowska &

Saroglou, 2011; Bushman, Ridge, Das, Key, & Busath, 2007; Ginges, Hansen, & Norenzayan, 2009; Henne, 2012; Johnson, Rowatt, & LaBouff, 2010; LaBouff, Rowatt, Johnson, & Finkle, 2012; Norenzayan & Shariff, 2008; Ramsay, Pang, Shen, & Rowatt, 2014; Saroglou, Pichon, Trompette, Verschueren, & Dernelle, 2005). This may explain why religion (as ethnicity) has also often been cited as a reason for between-group conflicts within or among societies and organizations with different faith-based beliefs. In political science literature, animosities between ethnic and religious groups has often been seen as the motive for the onset of conflict (Huntington, 1996; Reynal-Querol, 2002). Religious differences, even more than language or ethnic differences, are exclusive (one can speak two languages or be of mixed ethnicity but in most cases one only adheres to one religion) and imply different worldviews and social relationships. With homophily as a driving force in the background, individuals will tend to form network ties with others who share a similar set of beliefs that tend to be polarized along ideological or religious lines (McPherson, Smith-Lovin, & Cook, 2001).This connection may have grown stronger in recent millennia as part of the evolution of complex societies and competition for scarce resources (Scott Atran & Henrich, 2010). Huntington argues that religion

3 More long-term aspects of religion are detected in correlational analyses, leaving us with a number of alternative conceptualizations (belonging to a denomination, integration in the religious community, aspects of believing, having fundamentalist ideas, the share of Protestants in a country, religious diversity, etc) and potential confounds of religion over time, which all make it impossible to answer the question on the direct effect of worship on discrimination. Also, discrimination is not well covered in those correlational studies.

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is often the primary force that motivates and moves humans – not political ideology or economic interests – and one can more easily solve economic or political disputes than religious ones.

On the other hand, religious outgroup bias may simply be due to stereotyping or may be no different from using secular primes as group identity. Indeed a meta-analysis covering 77 experimental studies on discrimination found discrimination in about one-third of cases and that discrimination against the out-group was more likely when identity is artificially induced in the laboratory than when the subject pool is divided by ethnicity, religion or nationality (Lane, 2016).

This reasoning is in line with an economic explanation of conflict which does not see grievances and motives as driver for conflict but economic opportunities such as the possibility to extort natural resources (Collier & Hoeffler, 2004). Obviously, not all societies with religious polarization necessarily end up in a civil war. One way to overcome these identification problems at the fundamental micro level and to test whether religion is indeed a driver of conflict would be to show that outgroup bias increases with attending religious rituals. This is the approach we use in this paper.

Turning to literature that looks explicitly at religiously motivated conflict, self-reported measures of regular attendance at religious services indeed predicts out-group hostility and even willing martyrdom and religious ideology of a group greatly increases the number of deaths from a suicide attack (Ginges et al., 2009; Henne, 2012). Similar findings emerge for representative samples of religious Indians, Russians, Mexicans, British, and Indonesians: Greater ritual attendance predicts both declared willingness to die for one’s deities, and belief that other religions are responsible for problems in the world (Ginges et al., 2009). Similarly, religious priming can promote discrimination and prejudice or increase aggressive behavior towards strangers (Bushman et al., 2007; Johnson et al., 2010). In general, religion - just as any group – is likely to enhance commitment to coalitional identities, even independent from the religious belief per se (S. Atran, 2003; Bernhard, Fischbacher, & Fehr, 2006). In that sense, religious priming may affect behavior by increasing the salience of group identity (Charness, Rigotti, & Rustichini, 2007; Chen & Li, 2009; Eckel & Grossman, 2005). However, for methodological reasons, these studies do not allow concluding that religion is a driver of conflict. In order to circumvent these problems we test whether a religious stimuli, like worshipping, affects the outgroup bias.

Finally, with respect to evidence on participation in religious rituals and how that may affect social behavior, the empirical literature from outside the laboratory is ambiguous and has

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documented both a positive effect of participation in religious rituals with respect to donations as well as a negative effect of contribution in a public good game during Ramadan as compared to after Ramadan (Akay, Karabulut, & Martinsson, 2015; Xygalatas et al., 2013). However, none of the existing field studies have analyzed the effect of religious rituals on out-group discrimination.