When Nathalie Hallin, an atheist, and Hajdi Moche, a Christian, debated the roots of human generosity, they kept circling the same question: Does religion make people more willing to give? This was no idle philosophical musing. As postdoctoral researchers at Linköping University’s Department of Behavioural Sciences and Learning in Sweden, they decided to test it with science. Their findings reveal a truth that’s more nuanced — and perhaps more revealing — than either had imagined.

Their study shows that believers aren’t more or less generous than atheists. But that’s only as long as they don’t know what the receiver believes in. Scratch a bit deeper, and a person’s faith — or lack thereof — becomes a decisive factor in how much they are willing to give. It turns out people are significantly more generous when they know the recipient shares their beliefs.

Generosity (with Strings Attached)

Hallin and Moche, along with colleagues Gerhard Andersson and Daniel Västfjäll, conducted a series of experiments spanning three countries: Sweden, the United States, and a combined study in Egypt and Lebanon.

In Sweden, 398 participants were tasked with distributing fictitious money to themselves and three hypothetical strangers over several rounds. Each round included different details about the recipients, such as their hobbies, political views, and favorite movie genres. But in one pivotal round, the participants learned the recipients’ religious beliefs.

Across the board, both religious and non-religious participants gave roughly the same amount when they knew nothing about a recipient’s faith. But when religious information surfaced, believers became markedly more generous, especially to recipients who shared their faith. Even atheists showed a bias toward their own group.

“I was actually surprised because the only thing that unites atheists is that you don’t believe in a god,” Hallin reflected.

Across Cultures, a Pattern Emerges

To ensure their findings weren’t isolated to Sweden, the team replicated their study in the United States, with 700 participants, and in Egypt and Lebanon, with 600. The results were consistent: in-group religion (or in-group lack of faith), more than any other factor, influenced generosity.

In the U.S., Muslims were the most generous to fellow Muslims compared to Christians and atheists. The pattern appeared in Sweden too, though the smaller number of Muslim participants made conclusions less certain. In Egypt and Lebanon, Christians and Muslims displayed similar levels of in-group generosity. Cultural norms, societal roles, and local dynamics may explain these variations, but the trend was unmistakable — people are biased toward their own group and will factor this in when giving.

This finding, while striking, sidesteps easy moral judgments.

“As researchers, we find it interesting that the relationship to religion has such a strong impact on generosity and group feeling,” said Hallin. “But we are careful not to evaluate this.”

Generosity Beyond Money

The study raises a broader question: What does it mean to be generous? Hajdi Moche offers a thoughtful perspective.

“You can be generous in different ways,” she said. “You can be generous with time, with love, or with care. So, whether there is anything in religion that says you should be generous with money in particular is something to think about anyway.”

This research peels back layers of human nature, suggesting that beneath the seemingly simple act of giving lies a web of identity, belief, and belonging. We may strive to be impartial in our kindness, but our sense of community often has the final say.

The findings appeared in the journal Judgment and Decision Making.