In adolescents, we found sex differentiation in jealousy responses to infidelity scenarios at all ages from 16 to 19; males found the sexual aspect of imagined infidelity more distressing than adolescent females did

Investigating the emergence of sex differences in jealousy responses in a large community sample from an evolutionary perspective. Per Helge H. Larsen, Mons Bendixen, Trond Viggo Grøntvedt, Andrea M. Kessler & Leif Edward Ottesen Kennair. Scientific Reports volume 11, Article number 6485. Mar 22 2021. https://www.nature.com/articles/s41598-021-85997-7

Abstract: Sex differences in jealousy responses to sexual and emotional infidelity are robust in samples of heterosexual adults, especially in more gender egalitarian nations. However, investigations of when and how these differences develop have been scant. We applied two forced choice infidelity scenarios in a large community sample of high school students (age 16–19, N = 1266). In line with previous findings on adults using the forced choice paradigm, adolescent males found the sexual aspect of imagined infidelity more distressing than adolescent females did. Nevertheless, there was no effect of age on the jealousy responses, and age did not moderate the sex difference. There were neither any effects of three covariates (having had first sexual intercourse, being in a committed romantic relationship, and sociosexuality), neither as markers of pubertal maturation nor as psychosocial environmental stimuli. Future research needs to investigate even younger samples in order to specify at what age the sex difference in jealousy responses emerges.

Discussion

In a large community sample of adolescents, we found sex differentiation in jealousy responses to infidelity scenarios at all ages from 16 to 19. The jealousy responses were neither affected by sexual or romantic experiences nor by respondent sociosexual orientation. Prior to this study, it was known that in adult heterosexual samples there is a sex difference in responses to jealousy scenarios using a forced choice paradigm1. This sex difference has proven especially robust in Scandinavian young adult samples4,14,15. Previously only Shackelford et al.29 and de Visser et al.19 have considered the sex difference in romantic jealousy among adolescents. However, Shackelford et al.29 only included a small number of participants younger than 20 and de Visser et al.19 focused primarily on life-span development. None of these considered the ontogenetic development and emergence of the sex difference in romantic jealousy during adolescence specifically and in detail. The current study therefore set out to discover when these sex differences emerge in a large community adolescent sample. Further, we considered how relationship status, sexual debut and sociosexuality might moderate the development of the sex difference in romantic jealousy – indicators of both psychological and pubertal maturation or life history52 and relevant experiences3.

Although our sample represents the largest group of young adolescents yet studied, we were unable to detect at what age the sex difference comes online. There was no interaction with age. Further, despite what evolutionary theories predict3, there was neither any effect of relationship status, sexual status, nor sociosexuality on the development of sex differentiation of jealousy responses. None of our predictions were supported. The sex difference appears to develop earlier than age 16, and it is fully established at that age.

Suggesting that these results were obvious a priori is not convincing. The analyses of de Visser et al.19 and Shackelford et al.29 do not really allow for any extrapolation to the age group considered here, due to low number of participants in the relevant age and no specific attention to processes in the ages 16 to 19. The current data were also collected prior to de Visser et al.19. Nevertheless, an evolutionary perspective suggests that adaptations develop or come online strategically, just prior to being adaptive relevant32.

This leaves us with some evolutionary developmental conundrums. The increased male heterosexual sexual jealousy response seems to be present at an early age and not contingent upon the specific domain relevant experiences we measured in this study. What function this specific emotional response to sexual infidelity might have played in young males in an evolutionary context is therefore unclear. None of the current evolutionary psychology approaches has specified any function for increased male sexual jealousy in adolescents too young to be troubled with cuckoldry, which is the main function of male, heterosexual sexual jealousy. The acquisition of committed, long-term partners that young men were able to defend from older, more formidable rivals with higher status was most likely evolutionary rare35. Further, at lower ages, it is unclear what, if any function early adolescent males’ increased focus on physical aspects of their romantic partners’ infidelity should serve. It is possible that the developmental appearance of sexual jealousy simply prepares the individual for later life, serving no function during adolescence. However, the current findings warrant further theoretical development. If anything, increased emotionality in young males might put them in harm’s way from older, more formidable men, rather than improving any relevant paternal certainty. Nevertheless, at some point when moving towards younger ages, the responses the participants would be reporting on might not be the functional jealousy of adults, but some form of a proto-sexual jealousy, with other possible specific or deferred functions. This might also be reflected in “puppy love”53 or other roleplay type of love bonds between children.

Finally, our community sample evinced adequate variance in the different sexual and relationship experiences to detect any conditional developmental effects in jealousy responses. At this point we would need further studies of early puberty to address the question of the emergence and development of this sex difference. Based on these results, our preliminary conclusion must be that increased heterosexual male sexual jealousy matures primarily as part of puberty, independent of specific experiences. However, the function of this response at this age remains unclear, as it would seem it serves no anti-cuckolding function, while retaining, especially in concert with Young Male Syndrome tendencies54, the cost of violent conflict with more formidable older males.

Limitations and future research

While this is the largest, youngest adolescent sample to be studied with the forced choice paradigm, we were unable to discover the point in development when the sex difference emerges. Future studies therefore need to investigate jealousy responses in even younger samples. However, doing so would introduce ethical and methodological challenges. As we consider continually lower ages, the scenarios will at some age stop being meaningful, or developmentally relevant to the participants. We need to consider the possibility that the males’ increased proto-sexual jealousy develops early in puberty. Future studies should possibly also go beyond self-report and investigate specific design features of jealousy and their development in men and women using longitudinal designs, including other developmentally relevant factors. Such a design might better address causality than our cross-sectional design. However, in this first in-depth of the emergence of the sex difference of jealousy responses, our focus was not primarily on causes, but on at what age this difference appears. Also, the community sample consisted of four representative age cohorts55, and therefore ought to be adequate to address age trends. Further, the current approach to the development of jealousy is limited to test a specific set of predictions and does not address several other socio-cultural and intrapsychic factors, that may be of interest in future studies.

Conclusions from a Norwegian sample are admittedly culturally limited, to some degree56—and in any case subject to evolutionary mismatch57. Known cultural and socioecological variation that contribute to variation in jealous responses include more parental investment and less extramarital sex, which predict more severe jealousy responses across cultures12. Despite the importance of cultural and socioecological factors, similar forced-choice patterns have been found in cultures as diverse as China40, Korea58, Japan12,58, Sweden14, Norway4, England, Romania59, Germany, Netherlands60, Spain61, India, and among the Hadza, Himba, Karo Batak, Mayangna, Mosuo, and the Shuar12.

Finally, the current study suffers from the same limitations that hold true for all hypothetical scenarios, and the forced choice paradigm. Continuous measures and experienced jealousy may also be studied in the future in this age group.