People tend to reject unfair offers of water in a bargaining game, even when they have been experimentally induced to be thirsty, research published in the journal Scientific Reports indicates. The results suggest that humans care about being treated fairly when bargaining with primary rewards and hint that such reciprocal altruism may be particularly prominent in humans.
Humans bargaining over money tend to reject unfair offers, even at a cost to themselves, whereas chimpanzees bargaining over primary rewards of food do not show the same behaviour. But it has remained uncertain whether such reciprocal fairness represents a primarily human motivation and whether humans also reject unfair offers of primary rewards, such as food and water. Nicholas Wright and colleagues induced either moderate or severe thirst in 21 human participants using intravenous saline to determine how people’s responses to bargaining in the Ultimatum Game differ when they are working for a primary reward - water in this case - in a situation where desire for the reward has been induced.
They found that the participants tended to reject unfair offers of water, even in the case of severe thirst. The data also provide tentative evidence that humans may trade off this fairness motivation against their own subjective self-interest (the value of the primary reward to the individual).