It appears surprisingly, this impact isn't confined to romantic situations, and it also applies to how people behave when making purchasing decisions, indicating that fundamental evolutionary impulses can whimsically influence behaviour across various settings.
The sunk cost fallacy refers to the inclination to stick with a decision or investment because of the resources already put into it, even though it would be more sensible to cut losses when it's no longer in your favour. For instance, a person might carry on watching a film they're not enjoying simply because they've invested 60 minutes of their time. It is commonly seen as illogical because the cash and effort already committed (the "sunk costs") can't be got back, and choices should typically be guided by future outcomes rather than past spend.
Conventionally, explanations for this bias have centred on psychological and cognitive factors, such as the wish to avoid waste, fear of regret, or a requirement to justify earlier decisions. Nevertheless, some researchers propose that sunk cost bias may not always be unreasonable. From an evolutionary standpoint, committing to an investment might have been advantageous in contexts such as securing a mate and survival, where persistence and resource commitment indicated fitness and reliability to potential partners or guaranteed access to essential resources.
This evolutionary perspective is behind the purpose of the study. The researchers suggested that sunk cost bias might help in relationships, particularly in the case of men, who in the past have used aggressive and resource-demanding approaches to secure partners. They proposed that the driving force behind securing a partner could trigger an implemental mindset, a focus on achieving specific goals, that would increase the likelihood of sticking with prior investments, even in unrelated areas, like consumer behaviour.
To find out how mating motives impact the sunk cost bias, the researchers carried out one field study and seven laboratory experiments, six of which were registered in advance to provide clarity.
Researchers initially investigated any differences between men and women in regard to their vulnerability to sunk cost bias when it comes to matters of the heart. They enlisted the participation of 220 individuals, including 114 women, who were primarily aged 30.7 years on average, through a Chinese online survey platform. The participants were randomly divided into two distinct groups: one belonging to a romantic relationship scenario and the other to a consumption decision scenario.
In the romantic scenario, those taking part imagined they had spent over a month getting to know a potential dating partner through chat, had sent each other virtual gifts, and had organised to meet in person. Just before meeting face-to-face, they found out about a more attractive and a better-suited potential partner. They were then faced with the decision of whether to stick with their original partner or meet the new one instead.
The objective was to determine whether males tend to display a stronger sunk cost bias when it comes to romantic choices, but not when making consumer decisions. This design took account of possible confounding factors, such as perceived moral issues, which were assessed using ratings provided by the participants. This study found that men were more inclined than women to stick with a decision they had made, even if it seemed wise to change their mind, in a romantic scenario, laying the groundwork for further research.
Expanding on Study 1, the researchers investigated whether exposure to mating cues affected the tendency to persevere with a poor decision due to a sunk cost in unrelated areas, such as investments and spending choices. The study involved 231 heterosexual participants (150 women) with an average age of 25.3 years, recruited from the United States via a platform called Prolific.
Participants were randomly placed into one of two groups: a mating cue group or a control group. In the mating cue group, people judged how attractive they found images of potential dates and were asked to imagine going on a romantic date with someone they found appealing. In the control group, participants evaluated pictures of flats and were asked to imagine discussing renting the property with the landlord.
Afterwards, participants were asked to make decisions in two scenarios. In the investment scenario, they had to decide whether to continue funding a plane project that was mostly built but was now outperformed by a better alternative. In the consumption scenario, they decided between a concert for which they had a £100 ticket or a preferred concert with a £50 ticket. Mating cues significantly increased the 'sunk cost' bias among men in both scenarios, but had no impact on women, reinforcing the role of personal motives.
The researchers set up Studies 3a and 3b to establish a distinction between sunk cost bias, related to previous expenditure, and status quo bias, which is not. Study 3a involved 420 Chinese university students (233 women, with an average age of 23.1 years), recruited through a survey platform. Study 3b involved 561 participants (301 women, with an average age of 31.1 years) from the online platform Credamo.
In Study 3a, participants engaged in a task to gain a chance of winning a lottery (prior investment situation) or were provided with the lottery without their previous contributions (no prior investment situation). The attraction indicators were manipulated in the same way as in Study 2. Participants then decided whether to switch to a lottery with better odds. The research found that men’s sunk cost bias was higher in the prior investment situation when they were exposed to attraction cues, whereas no such influence was detected in the no-investment situation.
Study 3b utilised a restaurant booking scenario. In the preceding investment condition, participants had made a deposit; in the no-investment condition, they had made a free booking. As in Study 3a, displaying mating cues increased sunk cost bias in men in the prior investment condition but had no effect in the no-investment condition, thereby supporting the differentiation between sunk cost and status quo biases.
To investigate the underlying mechanism behind mating cues and sunk cost bias, the researchers conducted Studies 4a and 4b. They recruited 539 members (301 of whom were female, with an average age of 30.5 years) and 551 participants (302 of whom were female, with an average age of 30.6 years), respectively, through Credamo.
In Study 4a, participants described an upcoming activity they were planning to undertake and went through a mating cue manipulation, similar to previous studies. A mindset favouring implementation was measured with questions asking about participants' concern with detailed planning actions. The findings indicated that the presentation of mating cues strengthened a behaviour-focused mindset in men but had no such effect in women.
In Study 4b, participants' implemental mindset was manipulated. Those in the strengthened condition worked out steps to overcome a hypothetical problem, whilst those in the control condition simply described the problem. All participants then made a sunk cost decision about whether to continue a plane project. The findings revealed that an implemental mindset enhanced sunk cost bias for both men and women, demonstrating its role as a key factor.
Study 5 employed a process-by-moderation approach to verify the role of an implemental mentality in correlating mating cues and sunk cost bias. The sample comprised 572 individuals (305 females, with an average age of 31.8 years), recruited from the Sojump platform. Participants were presented with mating or control cues and then undertook an activity to alter their implemental mindset (for instance, selecting between two laptops, thereby stimulating goal-directed thinking).
People then made a decision to carry on watching a dull film after investing an hour. In a special test group, hints about interacting with a partner increased men's tendency to insist on continuing with something. However, in a separate test group where people were more focused on making things happen, the hints about a partner had no influence, as all participants seemed to be more willing to persist with the film. This outcome verified that being focused on making things happen made people more likely to do so.
The final study applied these findings in a real-world setting. The researchers collaborated with a university café, recruiting 240 Chinese students (120 females) over seven days. Participants were offered paid loyalty cards (5 RMB) with a 20% discount on coffee for two weeks. The cards featured either a romantic design (mating cue) or a neutral design (control).
The researchers monitored the use of these subscription cards and also conducted follow-up surveys to gauge participants' motivations and actions. The data showed that men who were shown romantic cards made use of their memberships more regularly, displaying a stronger tendency to persist with their investments in certain situations. In contrast, it seemed that the romantic design had no notable impact on women's behaviour, indicating distinct effects of mating motivations on investment persistence for both genders.
Together, the findings provide evidence that mating desires can have a significant impact on decision-making by activating a goal-oriented mindset, particularly among men. This mindset drives a stronger commitment to existing investments, manifesting as an irrational attachment to previous outlays, even in situations unrelated to mating.
The research points out key differences between men and women, which are rooted in how they've evolved to look for partners. Men are more likely to keep after what they want when they notice something they're interested in. These kinds of trends are not just limited to relationships - they can also be seen in the way people make choices about what to buy.
These discoveries also have significant implications for marketing and consumer behaviour, according to the researchers. For example, marketers could utilise romantic cues to enhance men's commitment to loyalty schemes or products requiring up-front investments. Nevertheless, the researchers go on to caution policymakers and consumers to be mindful of how such tactics might take advantage of psychological biases, leading to irrational financial decisions.
This paper was authored by Rui Chen, Hao Sun, Zhaoyang Guo and Haipeng (Allan) Chen.
