Bargaining and trust: the effects of 36-h total sleep deprivation on socially interactive decisions.

Although it is well known that sleep loss results in poor judgement and decisions, little is known about the influence of social context in these processes. Sixteen healthy young adults underwent three games involving bargaining ('Ultimatum' and 'Dictator') and trust, following total sleep deprivation (TSD) and during rested wakefulness (RW), in a repeated-measures, counterbalanced design. To control for repeatability, a second group (n = 16) was tested twice under RW conditions. Paired anonymously with another individual, participants made their simple social interaction decisions facing real monetary incentives. For bargaining, following TSD participants were more likely to reject unequal-split offers made by their partner, despite the rejection resulting in a zero monetary payoff for both participants. For the trust game, participants were less likely to place full trust in their anonymous partner. Overall, we provide novel evidence that following TSD, the conflict between personal financial gain and payoff equality is focused upon avoidance of unfavourable inequality (i.e. unfairness). This results in the rejection of unfair offers at personal monetary cost, and the lack of full trust which would expose one to being exploited in the interaction. As such, we suggest that within a social domain decisions may be more influenced by emotion following TSD, which has fundamental consequences for real-world decision-making involving social exchange.