Dating & Relationships

People Seem More Likely To Have Affairs Just Before Entering A New Decade Of Life

November 25, 2014 by Justin Lehmiller


A new set of studies just published in the Proceedings of the National Academy of Sciences concludes that when we are on the verge of entering a new decade in our chronological age (i.e., when we are ages 39, 49, 59, etc.), it prompts us to reflect upon the meaningfulness of our lives. This search for meaning leads some to the happy conclusion that their lives do indeed have meaning. For others, however, it leads to despair because they conclude that their lives lack meaning (which some might call a “midlife crisis”). In the latter situation, people can respond to this in one of two ways. Some will react in an adaptive fashion by pursuing behaviors that ultimately give their lives meaning or provide a sense of accomplishment, while others will respond in ways that are counterproductive and may hurt their chances of finding meaning. Of particular relevance to readers of this blog is the finding that one of those maladaptive coping mechanisms appears to be seeking out an affair.

In one of the studies reported in this article, the researchers gathered data from an online dating website that caters to people who are currently in relationships but are looking for, um, “extracurricular” activities. Specifically, they looked at the profiles of 8,077,820 men from this website who reported being between the ages of 25 and 64. They then examined the number of men who reported ages ending in each digit from 0 to 9 in order to determine whether people who had an age ending in 9 were statistically over-represented relative to other ages.

What they found was that ages ending in 9 appeared at an unusually high rate, comprising 952,176 total profiles. This is 18% higher than what would be expected if age had been randomly distributed.

The researchers focused on men in this analysis because they argued that men are more likely than women to have and seek affairs due to social constraints on female sexuality and also because affairs are more characteristic of the classic male “midlife crisis.” That said, they reported that an analysis of female profiles from this same site yielded similar conclusions, but the effect was not quite as robust.

Could these results be due to people lying and reporting ages ending in 9 in order to appear more attractive in their dating profiles? Probably not. The researchers conducted a separate study in which they asked 259 people between the ages of 25 and 64 to create a fake online dating profile designed to “fool a potential dating match into believing they were as young as possible while avoiding obviously fabricated responses because they might later meet that person.” Ages ending in 9 comprised only 6% of responses in this case. Statistically speaking, people were most likely to select a fake age ending in a 5 (21.5% of responses).

The results of this research are consistent with the idea that when people are on the verge of entering a new decade in life, they search for meaning in various ways. Although we focused here on how this may lead some people to seek out affairs (an approach that has a lot of potential to backfire), the researchers also found that others cope in more adaptive ways, such as by entering their first marathon. Thus, the implications of one’s search for meaning can be wildly different from one person to the next and having an affair may be just one of many ways that people act out.

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To learn more about this research, see: Alter, A. L., & Hershfield, H. E. (2014). People search for meaning when they approach a new decade in chronological age. Proceedings of the National Academy of Sciences.

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Written by
Dr. Justin Lehmiller
Founder & Owner of Sex and Psychology

Dr. Justin Lehmiller is a social psychologist and Research Fellow at The Kinsey Institute. He runs the Sex and Psychology blog and podcast and is author of the popular book Tell Me What You Want. Dr. Lehmiller is an award-winning educator, and a prolific researcher who has published more than 50 academic works.

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