Failure to act in this situation, Singer claimed, was fundamentally the same as failing to give money for famine relief. He called it unethical.

Not so fast, said John Arthur, then professor of philosophy at the State University of New York at Binghamton. Arthur pointed out that people often work hard for their money. He said it’s their money, and they have the right to do with it as they want. They have an obligation to give, he argued, only if it comes at no cost to themselves and their families. If people can use their money to make their own lives happier, then they shouldn’t give it away.

Today’s experts take a different view entirely.

Abhishek Rishabh, postdoctoral fellow at Northwestern University’s Golub Capital Social Impact Lab, studies how nonprofits can raise more money. He says that something as simple as a tedious donation form can dissuade people from giving.

“I can buy something with one click, but I can’t donate with one click,” he explains.

Another thing keeping potential donors from opening their wallets is a sense of doubt. Maddie Croucher, a behavioral science practitioner, says a major hurdle for would-be donors is “speculation whether your money is being used in an impactful way.” Rishabh agrees; he says people want to know that “their money is being used for something meaningful.” Both he and Croucher say this problem can be solved with what behavioral economists call a “nudge.” For instance, communicating about how donated money is used has been shown to alleviate such concerns and facilitate more giving.

When they are nudged, people certainly do give, and give generously, says Rishabh. He points out there’s a pervasive myth that low-income households give a larger proportion of their income to charity than their affluent counterparts. Pointing to a study by researchers at Texas A&M University, he says it is not true that the rich donate proportionately less than the poor. In fact, there is evidence suggesting that rich people are more likely to donate — though he concedes that today’s super-rich certainly have the capacity to give more.

Indeed, there is reason to be skeptical about the claim that people are fundamentally generous. Maxwell Burton-Chellew, evolutionary biologist and professor at Switzerland’s University of Lausanne, notes that the truth is more complicated. In experiments called “public goods games,” people demonstrate a tendency to give away money to others at their own cost. However, participants also tend to give away less and less money when the game is repeated in a second, third and fourth round. Some behavioral scientists see this as an indication that people learn over time that they can keep more for themselves, and choose to do so.