Conscientiousness The remaining two personality domains, conscientiousness and agreeableness, are often thought of as being unalloyed in their benefits, because they are generally negatively related to measures of delinquency and antisocial behavior (e.g. Heaven, 1996). However, it is important not to con- flate social desirability with positive effects on fitness. Natural selection favors traits that increase reproductive success, including many cases in which this success comes at the expense of other individuals. It is likely that fitness can be enhanced by a capacity to demand a free ride, break rules, and cheat on others under certain circumstances.