Previous research has implied that nice behaviour – dubbed “prosocial” behaviour by psychologists – almost certainly has a genetic basis. Gary Lewis and Timothy Bates at the University of Edinburgh’s Department of Psychology decided to investigate whether some specific prosocial behaviours – civic duty, work-place commitment and contributing to the welfare of others – were individually genetically determined, or whether there was some underlying common cause for these actions. The scientists analysed data from nearly 1000 sets of twins, whose level of prosociality in specific areas was determined by their answers to questions such as “how much obligation would you feel to testify in court about an accident you witnessed?”.
The researchers recognize that how nice we are could be affected by the environment we grow up in as much as our genetic makeup. However, studying identical and non-identical twins allowed them to disentangle these effects; while all sets of twins studied were brought up in the same environment, identical twins have the same genes whereas non-identical twins don’t.
The analysis revealed that although there are important differences between men and women in the influence of their genes on prosocial behaviour, the data also support the idea of a common genetic mechanism underlying all prosocial behaviour. As the scientists write, “It may be that selection for stable division of work, civil conflicts and welfare behaviours such as obligate food sharing have been important in shaping specific adaptations linked to in-group cooperation.”