Collective rituals are present in all known societies, but their function is a matter of long-standing debates. Field observations suggest that they may enhance social cohesion and that their effects are not limited to those actively performing but affect the audience as well. Here we show physiological effects of synchronized arousal in a Spanish fire-walking ritual, between active participants and related spectators, but not participants and other members of the audience. We assessed arousal by heart rate dynamics and applied nonlinear mathematical analysis to heart rate data obtained from 38 participants. We compared synchronized arousal between fire-walkers and spectators. For this comparison, we used recurrence quantification analysis on individual data and cross-recurrence quantification analysis on pairs of participants' data. These methods identified fine-grained commonalities of arousal during the 30-min ritual between fire-walkers and related spectators but not unrelated spectators. This indicates that the mediating mechanism may be informational, because participants and related observers had very different bodily behavior. This study demonstrates that a collective ritual may evoke synchronized arousal over time between active participants and bystanders. It links field observations to a physiological basis and offers a unique approach for the quantification of social effects on human physiology during real-world interactions.

Traditionally, ritual has been studied from broad sociocultural perspectives, with little consideration of the psychological processes at play. Recently, however, psychologists have begun turning their attention to the study of ritual, uncovering the causal mechanisms driving this universal aspect of human behavior. With growing interest in the psychology of ritual, this article provides an organizing framework to understand recent empirical work from social psychology, cognitive science, anthropology, behavioral economics, and neuroscience. Our framework focuses on three primary regulatory functions of rituals: regulation of (a) emotions, (b) performance goal states, and (c) social connection. We examine the possible mechanisms underlying each function by considering the bottom-up processes that emerge from the physical features of rituals and top-down processes that emerge from the psychological meaning of rituals. Our framework, by appreciating the value of psychological theory, generates novel predictions and enriches our understanding of ritual and human behavior more broadly.

Mounting evidence supports long-standing claims that religions can extend cooperative networks ^{1,2,3,4,5,6,7,8,9} . However, religious prosociality may have a strongly parochial component ⁵ . Moreover, aspects of religion may promote or exacerbate conflict with those outside a given religious group, promoting regional violence ¹⁰ , intergroup conflict ¹¹ and tacit prejudice against non-believers ¹² ,¹³ . Anti-atheist prejudice—a growing concern in increasingly secular societies ¹⁴ —affects employment, elections, family life and broader social inclusion ¹² ,¹³ . Preliminary work in the United States suggests that anti-atheist prejudice stems, in part, from deeply rooted intuitions about religion’s putatively necessary role in morality. However, the cross-cultural prevalence and magnitude—as well as intracultural demographic stability—of such intuitions, as manifested in intuitive associations of immorality with atheists, remain unclear. Here, we quantify moral distrust of atheists by applying well-tested measures in a large global sample (N = 3,256; 13 diverse countries). Consistent with cultural evolutionary theories of religion and morality, people in most—but not all— of these countries viewed extreme moral violations as representative of atheists. Notably, anti-atheist prejudice was even evident among atheist participants around the world. The results contrast with recent polls that do not find self-reported moral prejudice against atheists in highly secular countries ¹⁵ , and imply that the recent rise in secularism in Western countries has not overwritten intuitive anti-atheist prejudice. Entrenched moral suspicion of atheists suggests that religion’s powerful influence on moral judgements persists, even among non-believers in secular societies.