Is aversion to incest psychologically privileged? When sex and sociosexuality do not predict sexual willingness

Abstract

As human possess powerful incest-avoidance mechanisms (which likely evolved due to the high costs of inbreeding), reactions to incestuous sexual encounters may be psychologically distinct from reactions to non-incestuous (but still non-normative) sexual encounters. Accordingly, variables such as sex and sociosexuality that normally predict openness to sexual encounters in other situations (i.e., men and sociosexually unrestricted people tend to be more sexually willing) may not do so – or do so only weakly – in incestuous situations. In Study 1, sociosexuality predicted negative judgments of non-incestuous (but still normatively proscribed) sexual acts, but not judgments of incestuous sexual acts. In Study 2, sociosexuality predicted negative reactions to imagined sex with biologically unrelated (but still normatively unusual) partners, but not reactions to imagined sex with related partners (this effect was limited to women); also, men reacted less negatively than women to imagined sex with unrelated partners, but men and women reacted equally negatively to imagined sex with related partners (the latter effect was limited to sociosexually restricted men).