You are more likely to engage in casual relationships when you feel wealthy. At least, that seems to be the conclusion of a paper recently published in Evolution and Human Behavior.

The study examined preferences for a long or short-term relationship in 151 heterosexual volunteers with an almost even split between men and women (75 males versus 76 females). Specifically, the researchers wanted to find out how certain “evolutionary relevant” variables can affect mating preferences.

The volunteers were asked to consider relationships with 50 potential partners and place them into one of three categories: “a short-term fling” (one-night stand or brief relationship lasting days or weeks); “a long-term thing” (a commitment of months or years); or “nothing at all”, which is fairly self-explanatory.

They were then exposed to pictures of luxury goods (think money, mansions, fast cars, and jewelry) before being asked to categorize the images of potential partners into relationships once again. This process was repeated with parenting videos and images of dangerous animals.

The results suggest that wealth cues really do increase preferences for short-term relationships, though this doesn't detract from the probability of choosing a long-term partner if the right person comes along. The images of luxury goods prompted volunteers of both sexes to select more short-term partners by an average of 16 percent. Numbers of long-term partners were consistent with previous selections.

From an evolutionary perspective, it makes perfect sense. “[I]n environments which have lots of resources, it would have been easier for ancestral mothers to raise children without the father's help,” Andrew Thomas, a psychology professor at the University of Swansea and paper co-author, explained in a statement.

“This made short-term mating a viable option for both sexes during times of resource abundance. We believe modern humans also make these decisions."

In response to pictures of dangerous animals, both sexes showed an increased interest in long-term relationships. Whereas, rather stereotypically, women but not men chose more long-term partners after watching parenting videos.

The experiment was small-scale, with the vast majority of participants being white, childless, and in their early twenties, so it would be interesting to see how these trends play out in a larger, more diverse setup. Not to mention, whether or not a pay rise in the real-world has the same effect on our relationship preferences as exposure to a fast car in a lab setting. 

“Evolutionary psychologists believe that whether someone prefers a short-term relationship over a long-term one depends partly on their circumstances, such as how difficult it might be to raise children as a single parent,” said Thomas.

“Importantly, when those circumstances change, we expect people to change their preferences accordingly. What we have done with our research is demonstrate this change in behavior, for the first time, within an experimental setting.”