Short term, long term: An unexpected confound in human-mating research

Here I report that, when partnered people judge the facial attractiveness of potential mates for a short- and a long-term relationship, the order in which the two conditions are presented biases responses in a systematic manner. Women and men display symmetrical biases. Women find men less attractive as new long-term partners if they have first imagined them as one-night stands. Men find women less attractive as one-night stands if they have first imagined them as new long-term partners. On a total sample of over 3000 individuals from different studies, I show that both biases are robust and replicable in partnered people and neither is found in singles. Alas, so far no study has statistically controlled the effect of the order in which participants consider the two types of relationships. Whatever their interpretation, these biases are capable of producing spurious or inconsistent associations and mislead us when we compare studies that on the surface appear similar—most notably, direct and conceptual replications.