Those asked to report their experiences at romance noticed this increase in admirers, and approximately half reported being more attracted to a person who recently entered a new relationship

Burch, R. L., Moran, J. B., & Wade, T. J. (2020). The reproductive priming effect revisited: Mate poaching, mate copying, or both? Evolutionary Behavioral Sciences, jun 2020. https://doi.org/10.1037/ebs0000232

Abstract: According to the reproductive priming effect, an individual who enters into a romantic relationship tends to see an increase in admirers. To further understand the mechanisms underlying this effect and its relationship with mate poaching and copying, 560 undergraduates were asked to report their experiences of being a romantic target (i.e., experiencing more admirers when in a new relationship) or an admirer (having greater attraction for someone in a relationship). Over two thirds of respondents noticed this increase in admirers, and approximately half reported being more attracted to a person who recently entered a new relationship. Many of the responses indicated that this increased interest was a result of “jealousy” and reported that they wanted what they couldn't have. Behavioral changes were varied and correlated only weakly with the effect (both as admirer and target), which suggests that the attraction is mainly due to the target’s relationship status. Men were found to be seeking out other opportunities when in a new relationship, indicating a unique mating strategy.