People with insecure relationship habits tend to have more children, study finds

A recent study published in the International Journal of Psychology provides evidence that insecure attachment styles tend to be associated with having a higher number of children. The research suggests that cultural norms play a significant role in how our deep-seated relationship habits influence our family sizes. These findings challenge the assumption that a secure attachment style is always the most beneficial trait for reproductive success.

Attachment theory explains how early interactions with caregivers shape the way people relate to others throughout their lives. According to this framework, individuals develop working models of themselves and others, which guide their expectations in romantic partnerships and friendships. These relationship patterns generally fall into different styles, such as secure, fearful, preoccupied, and dismissing.

People with a secure attachment style tend to have positive views of themselves and others, which often allows them to build strong communication skills. This emotional foundation usually leads to stable, satisfying relationships that are well-suited for planned family growth. In contrast, insecure attachment styles involve various degrees of relational anxiety, emotional avoidance, or an unpredictable mix of the two.

Fearful attachment involves a negative view of both the self and others, often leading to a fear of rejection and difficulty maintaining partnerships. Preoccupied attachment is characterized by an overreliance on others for validation, which can result in highly dependent and conflict-prone relationships. A dismissing attachment style involves emotional detachment and a strong preference for self-sufficiency, often causing people to avoid deep emotional connections.

These relationship patterns not only influence romantic partnerships but also tend to shape parenting behaviors and family planning. “Attachment theory is one of the most influential frameworks in psychology, but discussions of it are often around emotional security and relationship quality rather than its generational consequences,” said Maryanne Fisher, a psychology professor and Santamarian Research Chair in Science at Saint Mary’s University in Halifax. Fisher is also an affiliate faculty member at the Kinsey Institute and co-author of the upcoming book Evolutionary Psychology: A Very Short Introduction.

The research team wanted to see if relationship patterns linked to family size in a uniform way around the world. “We were curious whether adult attachment styles link to reproductive success, meaning the number of children a person has, and whether any such pattern would look the same across different cultural settings,” Fisher explained. “Japan, Canada and the USA gave us three contexts with quite different family norms and fertility trends, which made for a useful test of whether attachment operates in a universal way or shifts with culture.”

Life history theory provides a useful lens for understanding these complex dynamics. This biological concept suggests that organisms adapt their reproductive strategies based on the stability of their environment. A fast life history strategy involves having more offspring with less investment in each individual child.

A fast strategy might be an adaptive response to unpredictable environments or relationship instability. On the other hand, a slow strategy involves having fewer children but investing more time and resources into each one. The scientists suspected that secure attachment might align with a slower reproductive strategy, especially in individualistic countries where autonomy and resource-intensive parenting are common.

To test these ideas, the researchers collected data from exactly 15,120 participants through an extensive online survey. The sample was evenly divided across three countries, with 5,040 respondents from Japan, 5,040 from Canada, and 5,040 from the United States. Within each country, the sample was split equally between men and women to ensure balanced representation.

The researchers also divided the participants equally across five specific age groups. These groups ranged from people in their twenties to those aged sixty and older. This equal stratification guaranteed that the scientists had enough statistical power to make meaningful comparisons across different generations.

Participants completed a standardized psychological tool used to measure adult attachment styles. The survey presented four short paragraphs, with each one describing a distinct relationship style. The participants used a seven-point scale to rate how well each description matched their own attitudes and interpersonal behaviors.

To measure reproductive success, the survey asked participants to report their actual number of biological children. The researchers also asked participants about the ideal number of children they would like to have. This dual approach allowed the authors to compare actual family sizes with personal reproductive goals across three distinct cultures.

The data analysis revealed that people with fearful and preoccupied attachment styles tended to have more children across all three countries. “Essentially, the attachment styles usually labeled insecure (i.e., fearful and preoccupied), were linked to having more children, and the pattern held in all three countries,” Fisher told PsyPost. She noted that secure attachment, often treated as the ideal, was linked with having fewer children in Canada and the United States, though not in Japan.

This negative association in North America suggests that securely attached individuals might prefer behaviors that lead to smaller, more planned family sizes. “This means that the attachment styles we tend to judge as less desirable do not necessarily carry a reproductive cost,” Fisher explained.

The association between fearful attachment and the number of children was actually strongest in Japan. At the same time, secure attachment showed no significant relationship with the actual number of children in the Japanese sample. “I have to admit, the divergence in Japan was interesting and really points to how cultural norms around family are influential,” Fisher said.

“So, while secure attachment predicted fewer children in Canada and the USA, there was no such finding for Japan, which suggests culture shapes how attachment impacts on family life, at least in terms of the number of children someone has,” Fisher noted. The authors propose that Japan’s collectivist values, combined with intense economic pressures and a national trend toward delayed parenthood, might override the influence of individual attachment styles. In such environments, external societal factors likely play a more dominant role in reproductive decisions than personal relationship habits.

The researchers also observed notable sex differences in attachment styles across the different cultures. In Canada and the United States, women scored higher in preoccupied attachment, while men scored higher in fearful attachment. These results align with traditional social norms in individualistic societies, where women are often encouraged to focus on relationship building and men are pushed toward emotional independence.

In Japan, the pattern was slightly different, with women scoring higher in preoccupied, secure, and dismissing attachment styles. This complex combination likely reflects the modern tensions Japanese women face as they try to balance traditional caregiving expectations with increasing pressures to succeed in professional careers. Japanese men scored highest in fearful attachment, emphasizing the local cultural expectations of emotional restraint and relational caution.

While the findings provide evidence linking relationship styles to family size, readers should keep the scope of the results in perspective. “The big thing to keep in mind is that with a sample this large, even small effects become statistically detectable, so readers should weigh practical significance separately from statistical significance,” Fisher explained. She added that these are general tendencies studied across thousands of people, not strong predictors of any single person’s number of children.

The study also features several methodological limitations that provide context for the results. “The design is correlational and cross-sectional, so it shows relationships and not cause, and some third factor might be interacting with both attachment style and reproductive success,” Fisher cautioned. This means it is impossible to say whether a specific attachment style directly causes a person to have more children.

Additionally, the methods relied entirely on people reporting their own feelings and histories. “The data come from online self-report in three industrialized countries, too, so we have to keep that in mind,” Fisher said. The researchers also used a short, four-item questionnaire to measure attachment, which might lack the precision of longer psychological surveys.

Moving forward, the research team hopes to expand their focus to different types of populations. “We would like to think about the role of culture more, especially in terms of how parenting varies considerably by community,” Fisher said. The current study relied on people from highly industrialized nations, which limits how universally the findings can be applied.

“Ideally, we would like to re-run the study with samples who are not WEIRD and who have natural fertility (meaning, they are not using hormonal contraception) to further examine the extent of the relationships,” Fisher explained. The acronym WEIRD stands for Western, educated, industrialized, rich, and democratic societies. Exploring these dynamics in non-WEIRD populations could help scientists see exactly how environmental factors interact with relationship habits on a global scale.

The study, “Attachment Bonds and Baby Booms: A Cross-Cultural Study of Reproductive Success,” was authored by Maryanne L. Fisher, T. Joel Wade, Hidenori Komatsu, Nobuyuki Tanaka, Hiromi Kubota, Rebecca Burch, Catherine Salmon, and David Widman.