“Why Are Some People More Jealous Than Others? Genetic and Environmental Factors”, 2021-08-27 ():
[see also “Individual esthetic Preferences for Faces Are Shaped Mostly by Environments, Not Genes”, et al 2015] Research on romantic jealousy has traditionally focused on sex differences.
We investigated why individuals vary in romantic jealousy, even within the sexes, using a genetically informed design of ~7,700 Finnish twins and their siblings. First, we estimated genetic, shared environmental and nonshared environmental influences on jealousy. Second, we examined relations between jealousy and several variables that have been hypothesized to relate to jealousy because they increase the risk (eg. mate-value discrepancy) or costs (eg. restricted sociosexuality) of infidelity.
Jealousy was 29% heritable, and non-shared environmental influences explained the remaining variance. The magnitude and sources of genetic influences did not differ between the sexes. Jealousy was associated with: having a lower mate value relative to one’s partner; having less trust in one’s current partner; having been cheated by a previous or current partner; and having more restricted sociosexual attitude and desire. Within monozygotic twin pairs, the twin with more restricted sociosexual desire and less trust in their partner than his or her co-twin experienced statistically-significantly more jealousy, showing that these associations were not merely due to the same genes or family environment giving rise to both sociosexual desire or trust and jealousy. The association between sociosexual attitude and jealousy was predominantly explained by genetic factors (74%), whereas all other associations with jealousy were mostly influenced by nonshared environmental (non-familial) factors (estimates >71%).
Overall, our findings provide some of the most robust support to date on the importance of variables predicted by mate-guarding accounts to explain why people vary in jealousy.
[Keywords: jealousy, twins, mate value discrepancy, trust, infidelity, sociosexuality, individual differences, genetics]
…3.4. Do these factors still influence romantic jealousy when controlling for familial confounding? The follow-up discordant-twin analyses showed that, within monozygotic twins, the twin with a more restricted sociosexual desire experienced higher jealousy (β = −0.18, p < 0.001, n = 455), and the twin who rated their partner more trustworthy reported lower jealousy (β = −0.15, p < 0.01, n = 224 discordant twins) than his or her co-twin. The effects of sociosexual attitude (β = −0.09, p = 0.08; n = 455), having been cheated on in the past (β = 0.08, p = 0.08; n = 196), having been cheated on in the current relationship (β = 0.02, p = 0.79; n = 17), and mate value discrepancy (β = 0.04, p = 0.50, n = 228), were not statistically-significant when controlling for genetic and shared environmental confounding. However, the regression betas from the discordant-twin design analyses were similar in size to the betas from the regression analyses with the full sample that were reported in Table 4. These co-twin control results should be interpreted in light of the far lower statistical power in these analyses compared to the regressions using the full sample.
The bivariate twin analyses showed that the majority of the association between jealousy and the predictors was influenced by nonshared environmental factors (all estimates above 71%) and not by familial factors, with the exception of the association between jealousy and sociosexual attitude, which was mostly explained by genetic factors (74%) (see right side of Table 3).
…Discussion:…The finding that familial environmental influences did not influence jealousy has theoretical implications. According to influential accounts of attachment theory, mental models of relationship expectations are transmitted from parents to children, through learning during infancy (2005; Van 1995; et al 2016; c.f., et al 2017), and these mental models later determine emotion reactions, including jealousy, towards perceived relationship threats in adulthood (2005; 1997). Our finding that variation in jealousy is not influenced by familial environmental factors, which includes parenting, is inconsistent with these accounts. An implication is that research that seeks to understand variation in—and the development of—jealousy should attend more to genetic and nonshared environmental influences than to shared environmental factors such as parenting behavior. However, one caveat is that a limitation of twin studies is that they do not control for genetic and environmental interplay (for example, parental genes shaping the twin’s family environment) which can confound the estimate of the influence of the family environment (Keller et al 201014ya). Therefore, it is safest to say that we found no influence of the family environment ‘independent of genetic factors’ (Turkheimer et al 200519ya).
In contrast to attachment theory’s parental transmission account, mate-guarding perspectives hypothesize that jealousy should be primarily influenced by factors that increase the risk of infidelity by one’s mate (2013). These will often be socio-ecological variables (eg. the attractiveness of one’s mate, or the number of rivals in one’s environment) which presumably derive more from the nonshared environment than the shared environment. Our finding of a substantial nonshared environmental influence on variation in jealousy is therefore consistent with mate-guarding accounts (though not uniquely consistent with those accounts). Note, however, that the estimate of the nonshared environment also includes measurement error.