Research | Autor

Religion and cooperative childcare

The more children we have, the less we can invest in each of them. That is mathematically inevitable and empirically supported. Religion may be a powerful force that bring together families as well as community members and help to share the costs of childcare. I am part of an international team of demographers, anthropologists, and religious scholars examining why the trade-off between quantity and quality is lower among religious people.

Publications

Chvaja, R., Shaver, J. H., & Bulbulia, J. A. (2026). Investigating the causal effects of religiosity on childbearing among U.S. adolescents using a three- wave longitudinal design. Scientific Reports, 16, 1–10. https://doi.org/10.1038/s41598-025-34358-9
Samore, T., Sosis, R., Shaver, J., Chvaja, R., Conrad, M., Hassan, A., Lynch, R. F., Schaffnit, S., Spake, L., Watts, J., Shenk, M. K., Sear, R., & Alam, N. (2026). Religious parents receive more alloparental aid in rural Bangladesh. Evolutionary Human Sciences, 8, 1–21. https://doi.org/10.1017/ehs.2025.10029

Chvaja R., Shaver J.H., Spake L., Hassan A., Alam N., Rai R.K., Sear R., Sosis R., & Shenk M.K. (2025). The role of parental religiosity in shaping paternal investment: Evidence from Bangladesh and India. Proceedings of the Royal Society B, 292(20251352). https://doi.org/10.1098/rspb.2025.1352

Chvaja, R., Spake, L., Hassan, A., Sear, R., Shenk, M. K., Sosis, R., & Shaver, J. (2025). Maternal religiosity and social support to mothers: Helpers’ religious identity matters. Religion, Brain & Behavior. https://doi.org/10.1080/2153599X.2025.2454705

Shaver, J. H., Chvaja, R, Spake, L., Hassan, A., Badje, J., Cerami, C., Prentice, A., Sear, R., Shenk, M. K., & Sosis Richard. (2024). Mothers’ religious involvement is associated with higher fertility, lower marental investments, but more alloparental investments. American Journal of Human Biology, 36(12), e24144. https://doi.org/10.1111/jssr.12920

Costly religious signaling

Religious behaviors are inherently linked to commitment to religious cooperative norms allowing others to encode such behaviors as honest signals of cooperative incentives. Research documents plausibility of such reasoning but crucial gap remains if one wants to generalize and theorize about costly signaling as integral element of evolution of religion. My research explores functioning of costly signals and its underlying psychology.

Publications

Lang, M., Ružičková, A., Čellárová, K., Kundtová Klocová, E., & Chvaja, R. (2026). Intuitive and deliberative processes underlying commitment signaling for cooperative assortment. iScience, 29(2), 114549. https://doi.org/10.1016/j.isci.2025.114549

Chvaja, R. (2024). Costly Signaling as an integral part of the systemic approach to religion: Critical assessment from within the field. Journal for the Cognitive Science of Religion, 10(1). https://doi.org/10.1558/jcsr.23765

Lang, M., Chvaja, R., & Purzycki, B. G. (2024). The role of costly commitment signals in assorting cooperators during intergroup conflict. Evolution and Human Behavior, 45(2), 131–143. https://doi.org/10.1016/j.evolhumbehav.2024.01.003

Chvaja, R., Chinchilla, J., Goméz, Á., & Lang, M. (2023). Religious costly signal induces more trustworthiness than secular costly signal: A study of pilgrimage to Santiago de Compostela. European Journal of Social Psychology, 53(6), 1294 – 1308. https://doi.org/10.1002/ejsp.2975

Lang, M., Chvaja, R., Purzycki, B. G., Václavík, D., & Staněk, R. (2022). Advertising cooperative phenotype through costly signals facilitates collective action [Registered Report]. Royal Society Open Science, 9(202202), 1–19. https://doi.org/10.1098/rsos.202202

Chvaja, R. & Řezníček, D. (2019). An Integrative Framework of Commitment Displays in Religious Systems. Human Ethology, 34, 41-52.

Insecurity and religion

It has been argued that during existential crises, people turn to their gods and engage in religious rituals. This is because religious beliefs and practices may help alleviate the burdens of hardship by reducing anxiety and fostering mutual support within communities. My research examines whether crises increase religiosity and explores the ways in which religion helps individuals cope with difficult times.

Publications

Chvaja, R. & Lang, M. (accepted manuscript). How Remote Conflict Shapes Religious Engagement: The Impact of Russian Invasion of Ukraine on Religiosity in Europe. Religion, Brain & behavior.

Lang, M. & Chvaja, R. (2024). Mechanisms of secularization: Testing between the rationalization and existential insecurity theories [Registered Report]. Collabra: Psychology, 1(10). https://doi.org/10.1525/collabra.126508

Chvaja, R., Murin, M., & Vorobyev, D. (2024). The effect of Covid-19 emergence on religiosity: Evidence from Singapore. Social Science Research, 108(102979), 1-18. https://doi.org/10.1016/j.ssresearch.2024.102979

Lang, M., & Chvaja, R. (2022). Examining the adaptive value of ritualized behavior in anxiogenic contexts. In J. E. Lane and Y. Lior (Eds.), Handbook of evolutionary approaches to the study of religion. Routledge.

Religion and morality

Religion has been long linked with morality. However, not all Samaritans are good and the association between religion and morality is not simple as it seems at first sight. In several projects, I investigate how religion transforms our moral realms by reinforcing our perception of moral norms as objective and independent on time, space, and cultures and how religious rituals may promote group moral hypocrisy by creating sharp borders between us and them

Publications

Chvaja, R. (2024). The impact of ritual participation on perceived moral objectivity: A longitudinal investigation of the U.S. adolescents. Journal for the Scientific Study of Religions, 63(4):773–790.

Chvaja, R., Horský, J., Lang, M., & Kundt, R. (2022). Positive association between ritual performance and perceived objectivity of moral norms. International Journal for the Psychology of Religion, 33(2), 115-135.

Chvaja, R., Kundt, R., & Lang, M. (2020). The effects of synchrony on group moral hypocrisy. Frontiers in Psychology, 11(544589).

Other publications

Chvaja, R. (2022). ‘Matt J. Rossano, Ritual in Human Evolution and Religion: Psychological and Ritual Resources’ [book review]. Religio, 30(1), 83-85.

Chvaja, R. (2020). Why did memetics fail? Comparative case study. Perspectives on Science, 28(4).

Ongoing research grants

Currently (2025-2027), I work on a project funded by Czech Science Foundation titled

'War-induced insecurity, religiosity, and social support among Ukrainian refugee mothers in the Czech Republic'

This project investigates how war-induced insecurity influences religiosity and its social functions during crises using the Russian invasion of Ukraine as a case study. Combining survey data from forced migrant mothers in the Czech Republic and secondary data on casualties resulting from Russian bombing in Ukraine, we will explore how war-related insecurity in the area of origin affects religiosity of forced migrants in the Czech Republic. Next, we will investigate how religion fosters cooperation, trust, and social capital among refugees. To that end, we plan to collect data from more than 2,000 Ukrainian refugees in the Czech Republic.

Information and registration form for participants are accessible in Ukrainian and Russian language