Parents invest differently in daughters and sons, study finds

A new study published in Human Nature reports that parents do not simply invest more in daughters or sons overall, rather, their investment differs by domain, with mothers, fathers, daughters, and sons showing distinct patterns.

Human parenting is unusual in the animal kingdom because it is long-lasting, costly, and often involves substantial care from both mothers and fathers. Much of the previous research on parental investment has focused on broad questions, such as how much time or money parents spend on children, rather than examining the many different ways parents invest in offspring. Yet human parenting includes much more than food, protection, and money. Parents also teach skills, offer emotional support, guide social behavior, shape moral values, encourage education, and provide advice about relationships and adult life.

Sid Dougan and colleagues examined whether these different forms of parental investment vary depending on both the sex of the parent and the sex of the child. Their study was motivated by an evolutionary framework suggesting that parents may invest differently in daughters and sons when those children have historically faced different adaptive challenges.

For example, daughters may receive more guidance around relationships and protection, whereas sons may receive more encouragement in athletics, competition, or practical skills. The researchers also expected mothers and fathers to differ in domains where their own experiences or sex-linked roles may have shaped different forms of parental expertise.

The researchers analyzed data from 105 adults, 49.5% of whom were female, who had originally been recruited as part of a longitudinal study of newlywed heterosexual couples. These couples were first recruited in 1989 through public records of marriage licenses issued in Washtenaw County, Michigan, USA. The present analyses used data collected at the second time point, when participants were in their third year of marriage. Participants ranged in age from 19 to 36 years, with an average age of 26. Most identified as white, and most reported being raised in suburban areas of the United States.

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Participants completed a 105-item questionnaire about parental behaviors they experienced while growing up. For each item, they rated separately how much the behavior was performed by their biological mother and biological father, using a scale from 0, meaning “not at all,” to 7, meaning “a great deal.” The authors then organized the parental behaviors into conceptually distinct domains.

After removing items that were too vague or overlapped across categories, the final measure included 73 behaviors grouped into 13 domains: mating and relationship guidance, athletics and physical training, mechanical and practical skills, social and moral guidance, competitive encouragement, sexual permissiveness, direct care and domestic support, bonding and emotional support, education and career support, protection, discipline and regulation, wisdom and life guidance, and material provisioning.

Overall, mothers provided more parental investment than fathers when all domains were averaged together, although this difference was especially clear for daughters. Daughters received more investment than sons in mating and relationship guidance, protection, and material provisioning. Sons received more investment than daughters in athletics and physical training, competitive encouragement, and sexual permissiveness. In other words, the findings did not suggest a simple pattern in which one sex received more parental investment overall. Instead, daughters and sons appeared to receive different kinds of investment.

The results also showed clear differences between mothers and fathers. Mothers invested more than fathers in direct care and domestic support, bonding and emotional support, social and moral guidance, discipline and regulation, mating and relationship guidance, and wisdom and life guidance. Fathers invested more than mothers in athletics and physical training, as well as mechanical and practical skills.

Some domains showed no meaningful sex differences, including education and career support, where mothers and fathers invested similarly and daughters and sons received similar levels of support.

Several interactions also emerged. Mothers showed a stronger daughter-focused pattern in mating and relationship guidance, whereas fathers showed stronger son-focused patterns in athletics and physical training, and mechanical and practical skills.

The authors noted that the sample was relatively small and drawn from a Western, educated, industrialized, rich, and democratic context (WEIRD), which limits how confidently the findings can be generalized across cultures.

The study, “Sex Biases in Patterns of Parental Investment,” was authored by F. Sid Dougan, William Costello, and David M. Buss.