I'm surprised that the article, while otherwise well-researched, doesn't even mention the Zahavi Handicap Principle.
In Zahavi's view, altruism is a form of signalling: the altruist is doing so well, they can afford to lose a good deal of material benefits. The altruist then benefits from the high regard of the peers who witnessed the facts (e.g. potential partners of the opposite sex).
From this perspective, the crucial step in the experiments presented is not the punishment, but the subsequent public exposure of the in-game behavior.
To even the playing field maybe? If you brag about how awesome you are, you're putting the pressure on everyone else to be as awesome. Some people don't like that ...
Good point. The less-than-outstanding will look less less-desirable mate material. But they still want the benefits of altruism. So a morality develops that says, "Do good things for others (that includes me), but keep it to yourself less the rest of us look bad in comparison and fail to find suitable mates."
The experimental design deliberately excludes this type of signal. Anonymous, non-repetitive, closed book.
It is not an argument against social signalling. Just that there is something else going on too.
In Zahavi's view, altruism is a form of signalling: the altruist is doing so well, they can afford to lose a good deal of material benefits. The altruist then benefits from the high regard of the peers who witnessed the facts (e.g. potential partners of the opposite sex).
From this perspective, the crucial step in the experiments presented is not the punishment, but the subsequent public exposure of the in-game behavior.