After Buss (1989) initiated research in the field, sex differences in individuals’ preferences for long-term mates have been extensively studied in evolutionary psychology. Numerous studies report robust sex differences such as (1) men have a stronger preference for a younger mate than do women, (2) women have a stronger preference for an older mate than do men, (3) women more highly value traits associated with resource acquisition (e.g., economic status and educational attainment) than do men, and (4) men more highly value physical attractiveness than do women. However, our replication of the study by Bech-Sørensen & Pollet (2016) did not show a significant sex difference in the preference for physical attractiveness among a Japanese sample; however, the other sex differences (e.g., age difference and resource acquisition ability) were significantly different (Study 1). We designed Study 2 to test whether the nonsignificant findings were an artifact of the item used to measure the preference for physical attractiveness. Study 2 showed that sex differences were not statistically significant. In addition, the effect of sex was significantly smaller than the pre-determined smallest effect size of interest (SESOI).
