Do you share your personally useless information if others may benefit from it?
Information is personally useless if its beholder cannot benefit from it unless she shares it with those who can exploit that information to increase their outcome. We study sharing such information in a non-strategic and non-competitive setting, where selfish and cooperative motives align together. Although sharing information is cost-free, the experimental results and computational modeling reveal that almost half of the subjects have a negative tendency toward sharing their personally useless information. In addition, sharing personally useless information is not correlated with subjects’ personality traits, their sensitivity to fairness of opportunities, and their level of cooperation. However, the more subjects believe others cooperate in the Public Goods Game, the more they share information for free to others. Surprisingly, when subjects are rewarded and get access to the information directly by their action, they share less information; they prefer to give partial information more than guaranteeing their confederates’ success even at the cost of less profit for themselves and the difference between sharing in rewarded and non-rewarded conditions is negatively correlated with subject’s openness. Furthermore, the computational modeling revealed that subjects’ decisions and their reaction times are best described by the model of self and other-regarding behavior rather than models of fairness. The subjects sensitivity to others’ payoffs in the model is correlated with their belief about others’ cooperation in PGG. Thus, under the assumption of value-based decision making, the results show that self and other-regarding utility functions can make subjects irrational in terms of payoff-maximizing.