How do people showcase their best traits to potential partners? According to a new study published in Evolutionary Behavioral Sciences, altruism might be part of the answer. In an online charity game, heterosexual individuals spent more time contributing to a shared goal when paired with members of the opposite sex. The findings highlight how small acts of generosity could be linked to romantic motivation, even in digital interactions.
Altruism, at first glance, seems to conflict with the principles of natural selection, which emphasize survival and competition. Evolutionary theories have historically explained altruism through mechanisms like kin selection (helping relatives to boost shared genetic success) and reciprocal altruism (expecting help in return). However, researchers suggest that altruism may also serve as an important factor in sexual selection. Behaving altruistically could signal desirable qualities, such as genetic fitness or parental potential, making individuals more attractive as romantic partners.
Previous research has shown that people are more altruistic in the presence of potential mates, such as by donating more to charity or performing other prosocial acts. This study sought to investigate whether these patterns extend to online interactions, with time spent serving as a measure of altruistic cost.
“It is important to understand how Behaving altruistically can be adaptive, so that the costs incurred by the altruist are outweighed by the benefits they get,” said study author Daniel Farrelly, a principal lecturer in psychology at the University of Worcester. “Being more desirable as a long-term partner is a key benefit for an altruist, so it is interesting to see in this online game that people are willing to incur a real cost to help another individual, if that other individual might be a potential mate they would like to attract.”
To investigate how altruistic behavior might be influenced by mating motivation, the researchers recruited 146 heterosexual participants (68 men and 78 women), primarily university students, through social media and online platforms. The study centered around the Free Rice game, an online platform where participants answer trivia questions to earn grains of rice donated to the World Food Programme. The time and effort participants dedicated to this game served as a measure of altruistic behavior.
Participants played two rounds of the Free Rice game, each with a hypothetical partner represented by a gender-specific username (e.g., “John123” or “Emma456”). These usernames clearly indicated whether the partner was male or female, enabling the researchers to simulate interactions with same-sex and opposite-sex partners. Participants were told they needed to collectively earn 600 grains of rice with their partner, though they could contribute as much or as little as they wished, with the implication that their partner would cover the remainder.
The order of partner presentation (same-sex or opposite-sex first) was randomized to control for potential biases. After completing each round, participants recorded the amount of rice they contributed and returned to the study platform for debriefing. The researchers then analyzed the amount of rice participants earned in each condition to assess whether the sex of the hypothetical partner influenced their altruistic behavior.
The researchers found a complex pattern of altruistic behavior. On average, participants tended to contribute more rice when paired with opposite-sex partners—suggesting a potential mating motivation—compared to same-sex partners. However, this effect depended on the order in which participants interacted with their partners. When participants interacted with opposite-sex partners first, they displayed significantly higher altruistic behavior than when they started with same-sex partners. Interestingly, when same-sex partners were presented first, participants’ contributions to opposite-sex partners did not show the same significant increase.
The findings supported the idea that altruism could function as a signal of desirable traits in mate choice. Both men and women exhibited this pattern, reinforcing the notion that altruism is a mutually valued trait in mate selection. Additionally, participants showed a tendency to reduce their altruistic behavior toward same-sex partners over time, possibly due to declining motivation, but maintained consistent contributions with opposite-sex partners.
“When people are primed to think that they are interacting with an attractive potential romantic partner, they are more likely to behave in a way that is helpful to that individual,” Farrelly told PsyPost. “This is even the case when they interact online, with no prospect of meeting that person. This shows how powerful the motivation is to display altruistic behavior to others, as this is an important trait we all look for in long-term partners.”
The findings align with previous research suggesting that altruism can function as a signal of desirable traits, such as parental potential or genetic quality, in mate selection contexts. Importantly, both men and women demonstrated this behavior, reinforcing the concept that altruism is mutually valued in mate choice.
While the study provides evidence for the role of altruism in mate choice, it has limitations. The use of gender-specific usernames to simulate romantic contexts may not have strongly activated mating motivations. Other studies have used more vivid methods, such as displaying photos of attractive potential partners or asking participants to imagine romantic scenarios, to elicit stronger responses. Additionally, participants in this study had no opportunity for future interaction with their partners, which could have reduced their motivation to act altruistically.
“This research is still too heteronormative,” Farrelly said. “It would be great to have more data and more research that looked at the mate preferences of homosexual and/or bisexual participants when it comes to altruism (and other mate choice traits).”
Future research could also examine how factors such as age, relationship status, and cultural background influence altruistic behavior in romantic contexts. Extending these findings to environmentally friendly behaviors could further illuminate how mating motivations drive altruistic acts.
“I am exploring this topic with an applied form of altruism that is a key global issue; pro-environmentalism,” Farrelly explained. “I am planning on exploring, with colleagues, how mating motivations can cause individuals to behave in more environmentally-friendly ways. This follows on from work I have done previously that found that we report more pro-environmental behaviors when interacting with attractive potential partners (Farrelly & Bhogal, 2021), and will now look at actual environmental behavior.”
“To do this we will use a novel measure of online pro-environmental behavior (Farrelly et al., 2024), and the hope is eventually to know more about the social influence that can increase sustainable behaviors. In doing so, it is my hope that potential interventions can be used that will lead to such increases, to the benefit of us all.”
The study, “Evidence of Mating-Motivated Altruistic Behavior in Time Spent on a Shared Online Task,” was authored by Theodore HibbertGreaves and Daniel Farrelly.
