Researchers studied the relationship preferences of 151 heterosexual male and female volunteers (75 men and 76 women) by asking them to look at pictures of 50 potential partners and to indicate whether they would prefer a long or short-term relationship with each.

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Then, they were shown a series of images of luxury items related to wealth, including fast cars, jewelry, mansions, and money.

Finally, the participants revisited the images of their potential partners and sorted them by their preferred relationship type again.

After viewing the wealth images, both male and female participants selected more partners for a short-term relationship compared to the original result – an increase of about 16 per cent.

“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 Andrew G Thomas, from Swansea University in the UK.

“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,” said Thomas, who led the research.

After participants were given cues that the environment had lots of resources, they became more likely to select individuals for a short-term relationship.

“We think this happened because humans have evolved the capacity to read the environment and adjust the types of relationships they prefer accordingly,” Thomas said.

For example, in environments which have lots of resources, it would have been easier for ancestral mothers to raise children without the father’s help.

This made short-term mating a viable option for both sexes during times of resource abundance.

“We believe modern humans also make these decisions,” Thomas said.

The researchers also found that participants changed their relationship preferences after being shown a slideshow of dangerous animals, and videos of people interacting with infants.

“When the participants were given cues that the environment contained young children, they were more likely to select individuals for a long-term relationship,” said Thomas.

“Dangerous environments seemed to cause both men and women to choose more long-term partners, though some women chose more short-term partners instead,” he said.