In a previous post we talked about why celebrities cheat in their relationships. But what about the rest of the world? Why would “normal people” cheat? Certainly there are many things that contribute to relationship infidelity. One potential contributing factor is that one’s partner doesn’t provide enough new and exciting experiences within the relationship, or what researchers call self-expansion. When one’s partner provides insufficient opportunities for self-growth within the relationship then individuals report a greater inclination for cheating on their partner in order to fulfill their needs.1 Basically, if your own partner isn’t going to help you grow as a person, you’ll feel the need to shop around to find someone that will. To find an alternative partner that can meet those needs, you’d likely need to do a bit of window-shopping.
In fact, a major threat to the stability of a relationship is an attractive interloper (which is just fancy for some other person who may steal your partner) who may undermine your partner’s faithfulness.2 A person who is already experiencing low self-expansion may be especially vulnerable to an attractive interloper. To test this, Laura VanderDrift and colleagues had people in a current relationship rate the relationship’s ability to provide self-expansion (i.e., new and exciting experiences). They then gave the participants a chance to interact with someone that could have been an alternative partner.3 In reality, they interacted with a computer that provided preplanned answers that suggested a great deal of self-expansion. For example, if participants asked “Do you like to hear different perspectives on topics?”, the program responded “Yes, it keeps life interesting.” Not surprisingly, those who had actual relationships with less self-expansion enjoyed the scripted interaction more, and picked more questions that would assess the potential partner’s ability to provide self-expansion.
In a follow-up study, nearly 150 participants rated their own self-expansion and then were given a chance to participate in a “get acquainted” activity with highly attractive single partners. Participants knew they could select as many or as few people to interact with as they wanted. How many should they pick? Assuming they were happy and committed…ZERO! If you are in a happy and self-expanding relationship, it is probably a terrible idea to pick anyone because you might be tempted to do more than just chat. As with the previous study, those in less self-expanding relationships selected more potential interaction partners. These studies are important because people are less likely to consciously make the decision “today I’m going to cheat on my partner!”, even if their relationship isn’t very expanding. Instead, they likely engage in a series of behaviors that increases the chances of it happening, starting with paying more attention to alternate partners.
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1Lewandowski, G. W., Jr., & Ackerman, R. A. (2006). Something’s missing: Need fulfillment and self-expansion as predictors of susceptibility to infidelity. Journal of Social Psychology, 146, 389-403.
2Le, B., & Agnew, C. R. (2003). Commitment and its theorized determinants: A meta-analysis of the investment model. Personal Relationships, 10, 37-57.
3VanderDrift, L. E., Lewandowski, G. W., Jr., & Agnew, C. R. (2011). Reduced self-expansion in current romance and interest in relationship alternatives. Journal of Social and Personal Relationships, 28, 356-373. doi: 10.1177/0265407510382321
Dr. Gary Lewandowski – Science of Relationships articles | Website
Dr. Lewandowski’s research explores the self’s role in romantic relationships focusing on attraction, relationship initiation, love, infidelity, relationship maintenance, and break-up. Recognized as one of the Princeton Review’s Top 300 Professors, he has also authored dozens of publications for both academic and non-academic audiences. 
Rease Heart says
Really interesting.
I would assume the drive for self-expansion is a personality trait, more present in some people than others.
As a consequence, some people would be more likely to cheat based on self-expansion than others depending on their own internal drive for self-expansion.
Has it been tested? How do you determine the drive for self-expansion in a person? Would it be linked to intellectual, emotional or spiritual curiosity vs appreciation of routine and predictability?
Gary Lewandowski says
You raise a really interesting question. To this point, research on the self-expansion model has focused on the experience of self-expansion rather than individual differences in the desire for expansion. Basically a state approach, rather than a trait approach. That is not to say that there aren't individual differences. I suspect there are, but they have yet to receive much (if any) empirical attention.
Paul says
I find it interesting how many people seemingly look to the "other" to fulfill their needs, whether it be "needs" of self-expansion, validation, esteem, etc. Thank you for your article.