In humans and other mammals, defensive responses to danger vary with threat imminence, but it is unknown how those responses affect decisions to help conspecifics. Here, we manipulated threat imminence to investigate the impact of different defensive states on human helping behaviour. Ninety-eight healthy adult participants made trial-by-trial decisions about whether to help a co-participant avoid an aversive shock, at the risk of receiving a shock themselves. Helping decisions were prompted under imminent or distal threat, based on temporal distance to the moment of shock administration to the co-participant. Results showed that, regardless of how likely participants were to also receive a shock, they helped the co-participant more under imminent than distal threat. Reaction times and cardiac changes during the task supported the efficacy of the threat imminence manipulation in eliciting dissociable defensive states, with faster responses and increased heart rate during imminent compared to distal threats. Individual differences in empathic concern were specifically correlated with helping during imminent threats. These results suggest that defensive states driving active escape from immediate danger may also facilitate decisions to help others, potentially by engaging neurocognitive systems implicated in caregiving across mammals.
Keywords: altruism; defensive state; fear; fight-or-flight; freezing; prosocial.