By Christian Jarrett

People have a basic drive to learn and develop and to see themselves and the world in new ways. That’s according to the psychologists Arthur Aron and Elaine Aron, who refer to this as our need for “self-expansion”. It follows from their theory that any chance to self-expand should be rewarding, and that if you can self-expand while doing things with your romantic partner then your relationship will benefit. Previous research has hinted that this is the case, finding that when couples engaged in self-expanding activities together – anything that felt new, exciting, interesting and/or challenging – their satisfaction with their relationship increased.

Now in a paper in Journal of Personality and Social Psychology Amy Muise at York University and her colleagues have taken things further, laying out evidence that a major part of the reason that participating in self-expanding activities is good for relationships is that it boosts your sexual desire for your partner and increases the likelihood you will have rewarding sex – and, moreover, that this is particularly the case for people in long-term relationships.

For two 21-day diary studies, the researchers recruited over 200 couples who had been in an exclusive relationship (most of them heterosexual) for an average of 8 years (the first study) or 5 years (the second).

Each night the participants recorded on their own whether they had engaged in self-expanding activities with their partner that day (they answered questions like “How much did being with your partner expand your sense of the kind of person you are?” and “How much did you feel you gained a larger perspective on things because of your partner?”), and – in the second study only – they gave a specific example of an activity, if any, that they did with their partner that day that led to feelings of excitement, greater awareness, an expanded sense of self, and/or increased knowledge of the self and the world (see examples below). Participants also answered questions about their mood that day, overall time spent with their partner, their relationship satisfaction that day, their sexual desire for their partner, sexual satisfaction, and any sexual activity.

The results across the two diary studies – the first conducted in Canada, the second in the USA – were similar: On days that participants reported engaging in more self-expanding activities with their partner, they also reported more sexual desire for their partner, were more likely to have sex, and to feel satisfied with that sex and their relationship. These associations were stronger for couples who’d been together longer. “Having new experiences with a long-term partner may be more important to spark some of the feelings of desire and excitement from the early stages of relationships, feelings that may be harder to recall for couples who are in longer compared with shorter relationships,” the researchers said.

There were also some “dyadic effects” – that is, one person’s greater feelings of self-expansion were also associated with their partner tending to report greater sexual desire (perhaps because their partner was attracted by seeing them in a new light or seeing them undertaking new challenges), and both one’s own and one’s partner’s higher feelings of self-expansion were related to a greater likelihood of having sex.

The findings mostly remained statistically significant after controlling for any daily changes in mood, feelings of closeness, and time spent together; and a mediation analysis suggested that increased sexual desire was driving the association between greater feelings of self-expansion and increased sexual activity. Across the two diary studies, on days that self-expansion scores were high, the couples were between 25 and 34 per cent more likely to have sex.

The diary research hinted at the direction of the causal effects in the measured outcomes – for instance, more self-expansion today was associated with more relationship satisfaction tomorrow, whereas the reverse was not true (relationship satisfaction today did not predict more self-expansion the next day). However, to test the causal role of self-expanding activities more explicitly, the researchers conducted a final experimental study.

Over a weekend, the researchers tested whether coaching 51 couples to engage in more self-expanding activities together would lead them to experience the beneficial effects implied by the diary studies (the instructional advice came in the form of a fabricated magazine article that described the benefits of engaging together in new and exciting activities). For comparison, 65 couples looked at a fabricated article about the benefits of doing familiar things together, while another 82 couples acted as a no-intervention control and received no information.

Measures taken at the end of the weekend showed that couples who read the self-expansion article heeded the advice and engaged in more self-expanding activities together; they were also the only group to enjoy a boost in sexual desire over the weekend compared with before, and there was also a non-significant trend for them to have more sex than couples in the other groups (75 per cent of the self-expansion couples said they’d had sex over the weekend, compared with 63 per cent in the familiar condition, and 58 per cent in the no-intervention control condition). The self-expansion couples also reported higher levels of sexual desire and relationship satisfaction than the no-intervention control couples, but not more than the couples encouraged to do familiar things.

Critics may look at some of the examples of self-expanding activities that participants most frequently described in the second study (see above) – such as having a pizza and watching TV together, doing household chores together, or even, although less often, having an argument – and wonder where the feelings of self-expansion came from. What made some couples perceive such apparently mundane activities as self-expanding? The current research does not have any answers to this question, other than that the type of self-expanding activity and how physically arousing it was (as coded by researchers), did not appear to make any difference to the results.

Perhaps the unexceptional nature of some of the activity examples suggests that, before rushing to book that tandem bungee jump or hot-air balloon ride, it is worth considering that the secret to self-expansion lies not so much in the precise nature of the activities you undertake together, and more in your perceptions of what you do and in the attitude and the mindset you bring – especially whether you can find the magic and mystery in the mundane. Exploring more about when and why and for whom this mindset is possible is for future research to consider. For now, Muise and her team conclude that “one way couples can promote desire in their relationship, and in turn, their relationship satisfaction and sexual connection, is by engaging in self-expanding activities together.”

—Broadening your horizons: Self-expanding activities promote desire and satisfaction in established romantic relationships

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest