Study Suggests Adults With Insecure Attachment Styles May Have Larger Families

People with insecure attachment styles in adulthood may have more children than those with secure attachment styles, according to a large cross-cultural study published in the International Journal of Psychology. The research compared relationship patterns and family size among adults in Japan, Canada, and the United States.

The findings suggest that attachment patterns established early in life may subtly influence reproductive behavior, although the relationship varies considerably across cultures. They also challenge the common assumption that secure attachment necessarily leads to greater reproductive success across generations.

Attachment Styles and Family Patterns

Attachment theory proposes that early experiences with caregivers shape internal models of how people relate to others throughout life. In adulthood, attachment is commonly categorized into four styles: secure, fearful, preoccupied, and dismissing. Each is characterized by distinct expectations about intimacy, trust, and emotional closeness.

People with secure attachment generally have positive views of themselves and others, communicate effectively, and tend to establish stable, long-term relationships. In contrast, insecure attachment styles—including fearful and preoccupied attachment—are associated with greater anxiety about rejection, emotional instability, or an increased need for reassurance, all of which can place strain on romantic relationships.

Despite these challenges, the new study found that fearful and preoccupied attachment styles were consistently associated with having more children. This pattern was observed across all three countries, suggesting that personality traits often viewed as socially disadvantageous do not necessarily reduce reproductive success.

How the Study Was Conducted

The researchers surveyed 15,120 adults through an online questionnaire, including 5,040 participants each from Japan, Canada, and the United States. Each national sample was evenly balanced by sex and distributed across five age groups, ranging from participants in their twenties to those aged 60 years and older.

Participants read four brief descriptions representing the different attachment styles and rated how accurately each described them using a seven-point scale. They also reported both the number of biological children they had and the number of children they considered ideal, allowing researchers to compare actual and preferred family size.

The authors then examined whether attachment style scores were associated with the number of children and whether these relationships were consistent across countries with markedly different fertility rates and cultural expectations surrounding family life.

Insecure Attachment Was Linked to Larger Families

Across Japan, Canada, and the United States, higher scores for fearful and preoccupied attachment were associated with having more children. These insecure attachment styles remained linked to greater reproductive success even after accounting for other variables included in the analyses.

By contrast, secure attachment did not consistently predict larger families. In both Canada and the United States, individuals with higher secure attachment scores tended to have fewer children, suggesting that people in these more individualistic societies may favor smaller, more deliberately planned families.

Japan showed a different pattern. Secure attachment was not significantly associated with family size, while fearful attachment demonstrated the strongest positive relationship with the number of children. According to the researchers, this finding highlights how cultural and societal pressures can modify the influence of psychological characteristics on reproductive behavior.

Life History Theory May Help Explain the Findings

The authors interpret their results using life history theory, which examines how organisms allocate resources between growth, survival, and reproduction. In unpredictable or unstable environments, a "fast" life history strategy often favors having more children while investing fewer resources in each child.

Conversely, in stable, resource-rich environments, a "slow" strategy typically emphasizes having fewer children while investing more heavily in each child's development. Secure attachment, which supports long-term planning, cooperation, and stable relationships, appears to align more closely with this slower reproductive strategy in North American societies, where intensive parenting is common.

In Japan, however, factors such as persistently low birth rates, demanding work culture, delayed marriage, and high childcare costs may weaken any direct association between secure attachment and family size. These economic and social pressures may outweigh the influence of individual attachment patterns.

Gender Differences Across Cultures

The study also identified several gender differences in attachment styles.

In both Canada and the United States, women scored higher on preoccupied attachment, whereas men scored higher on fearful attachment. These findings are broadly consistent with cultural norms that encourage women to invest heavily in close relationships while encouraging men to appear emotionally independent.

In Japan, women scored higher not only on preoccupied attachment but also on secure and dismissing attachment. The authors suggest this combination may reflect the tension between traditional caregiving expectations and increasing pressure for women's educational and professional achievement.

Japanese men demonstrated the highest fearful attachment scores, consistent with cultural expectations that encourage emotional restraint.

These findings suggest that attachment styles are influenced not only by childhood experiences but also by broader social and gender norms. Consequently, the relationship between attachment and reproductive behavior may vary according to what is socially accepted or encouraged within different cultures.

Limitations and Future Research

The researchers emphasize that although the observed associations were statistically reliable, their effect sizes were relatively modest. Attachment style represents only one of many factors influencing how many children people ultimately have and should not be viewed as a strong predictor for any individual.

Because the study was cross-sectional and correlational, it cannot establish cause-and-effect relationships. Other variables, including socioeconomic status, childhood adversity, or early-life stress, may influence both attachment style and fertility.

The authors also note that attachment was measured using brief self-report questionnaires and that the study included only highly industrialized countries. These so-called WEIRD (Western, Educated, Industrialized, Rich, and Democratic) populations may not reflect the diversity of family structures and reproductive behavior observed worldwide.

Future research should include populations with natural fertility patterns, where contraception is uncommon, as well as non-WEIRD societies with different cultural, economic, and environmental conditions. Such studies could help clarify how attachment styles interact with local circumstances to influence reproductive behavior.

Overall, the findings add a new perspective to attachment theory by suggesting that attachment styles may have consequences that extend across generations. They also indicate that personality traits often considered disadvantageous in romantic relationships may persist partly because they are not strongly associated with reduced reproductive success.

By Victoria Caldwell.