Civic honesty around the globe

At first I thought it was counterintuitive.

But after self-reflection, I'm more likely to report it if it did have money.

If it had money, I'd feel an obligation to protect it and return it to the owner. If it didn't, I'd feel more like it's their problem.

I don't find it counterintuitive at all. It's just less of a big deal to lose a wallet that has no money in it than one that does have money in it.

In only one case do you actually lose money. Both cases require the same effort to make contact.

For the civic-honesty-minded person who has to balance that effort cost to themselves against the victim's loss, there's going to naturally be a stronger impulse to help the person who stands to lose more.

They controlled for exactly what you are saying. They added a key which has value only to the wallet owner and not the finder. There was not as big of an increase in returns. This led them to conclude the more likely explanation was the “I’m not a thief” reasoning.