Altruism significantly increased female attractiveness rating for long-term relationships. The effect of altruistic versus neutral traits on female attractiveness for long and short term relationships. Cards were rated for attractiveness (on a 9-point Likert scale) and where the altruism card was shown in one trial, the neutral was shown in the other. The graphs show the least-square mean (± SE) change in attractiveness between trials (trial 2 value minus trial 1 value) with positive values indicating that the rating was higher in the 2nd trial than in the 1st trial. Bars with different letters above them are significantly different from each other using Tukey corrected multiple comparisons.