Very nice and unintuitive main finding. I wish there was a separate condition where they sent a second experimenter back to the location of the hand-in to ask for the wallet. Just waiting for a contact leaves some room for unpredictable effects: perhaps with no money, the person can't even be bothered to deal with it. With money, there is an incentive to try to contact in the hope that if no response is received within a short period, the money can be kept.
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