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What makes love last?


Dr. David Schmitt looks at the origins of his interest in relationship psychology—and where that interest has taken him.


As an undergraduate, I decided on a whim to take a course on personality psychology. I was a physics major interested in predicting the behavior of satellites and comets, but once I discovered one could legitimately use scientific measures and statistical tools to accurately predict the behavior of humans, I was hooked.

"Across the ISDP, we found many results from the USA replicated around the world. However, it was the differences in findings across cultures that were most interesting."
Dr. David Schmitt

I eventually took several courses in personality and social psychology, writing term papers and conducting small in-class studies on personality and behavior. One of my favorite term papers was, "Why is it that some couples do well together, whereas others drift apart after only a few months?" I reviewed evidence in that paper showing the degree to which newlywed couples are similar in personality relates to whether couples are satisfied with their relationships years later. In one research study, my classmates and I tested a theory regarding why we are attracted to some people more than others, and why what is considered attractive varies among people and across cultures and socio-demographic statuses. I found that gender differences existed in what men and women desired in potential sexual partners, but that these differences were smaller within certain ethnicities, socioeconomic groups, and personality types.

Researching relationships

This curiosity in the psychology of personality and romantic relationships carried over to my graduate education. As a graduate student, I helped conduct several studies of married couples and came to learn that certain personality traits are more important than others in determining what people desire in potential partners and whether or not a romantic relationship lasts. For instance, highly disagreeable and neurotic people are not preferred and tend to make bad romantic partners, but if they are partnered with others who also are disagreeable and neurotic a relationship can endure. Today, and make claims about the importance of "personal compatibility," and in fact some scientific evidence exists to back such claims.

After arriving at Bradley University in the late 1990s, I developed several new measures of peopleís "sexual personalities" and investigated whether certain sexual attitudes and behaviors also play important roles in romantic relationship outcomes. In a study of 48 dating couples, my students and I found that individuals who are disagreeable and extroverted tend to have permissive or "unrestricted" sociosexual attitudes (i.e., they tend to feel positively toward engaging in casual sex). Individuals who are disagreeable, extroverted, and low in conscientiousness are more likely to also be unfaithful and to engage in acts of "mate poaching" (or stealing another personís romantic partner). These personality-relationship linkages are interesting because psychologists can use what is known about the developmental and physiological origins of these traits to better understand the who, what, where, when, and how of romantic relationships going wrong.

The International Sexuality Description Project

I began collaborating with psychologists from Europe and Asia to see if the personality-relationship linkages found in the USA would replicate across cultures. Too often, research from Western cultures is assumed to be "universal" without regard for the important influences of culture. In 2000, I assembled a large team of over 100 psychologists, sociologists, biologists, and other researchers to study sexual attitudes and behaviors across cultures. This team included researchers from 56 nations. I called this research the International Sexuality Description Project (ISDP). Our main goal was to investigate how culture, personality, and gender combine to influence sexual attitudes and behaviors (e.g., why are some people dutifully monogamous, whereas others are rampantly unfaithful).

In the ISDP, my colleagues and I simultaneously administered surveys to college student and community samples across all nations. We asked about peopleís personality traits (e.g., self-esteem: "Do you like yourself?"), sexual attitudes (e.g., sociosexuality: "Do you think that casual sex is OK?"), and sexual behaviors (e.g., mate poaching: "Have you ever tried to romantically attract someone who is already in a relationship with someone else?"). With the help of over a dozen Bradley students, we were able to combine all these responses into a usable dataset for addressing whether previous research findings replicate across cultures.

Across the ISDP, we found many results from the USA replicated around the world. However, it was the differences in findings across cultures that were most interesting. For example, although men were more likely to think that casual sex is OK than women in every culture, the degree to which men and women differed depended on the sociopolitical gender equality of the local culture. In more progressive or "gender-egalitarian" cultures (e.g., Finland), gender differences in sociosexuality were smaller. In more traditional cultures (e.g., Botswana), gender differences in sociosexuality were larger. We also found that self-esteem was linked to sociosexuality differently for men and women, and differently across cultures among women. In the USA men who were positive toward casual sex tend to have higher self-esteem, whereas women who were positive toward casual sex have slightly lower self-esteem. This is typical of most cultures, but women from Eastern European cultures who have positive attitudes toward casual sex have higher self-esteem.

My students and I have published several papers using this cross-cultural ISDP dataset, including papers on self-esteem, sociosexuality, and mate poaching. I plan to continue such research, always with an eye on explaining the eternal question of why some relationships last and others do not.

For a list of Dr. Schmitt's recent publications and findings of the ISDP, see