Variation in the Sunk Cost Effect in Humans with Different Development and Animals

    The way humans make decisions is a complex process, but most people would agree with the suggestion that we account for the consequences we might face in the future when making a decision. In the fast-paced age that we currently live in, it is important that we make the right choices throughout the day in order to avoid wasting time or money­–and risk regretting our decisions. We may think we have this ability under control, but what if future costs are not the only factor that influences our decision-making? Research has shown that humans, as well as animals, can be influenced also by their past costs during decision-making. This phenomenon is known as the sunk cost effect. Sunk costs can be described as the resources or time spent while pursuing a specific task that cannot be recovered afterwards. The idea is that, even if a certain activity no longer seems productive to us, we will be more hesitant to quit based on how much of our resources we invested in it. That investment can be in the form of money, time, or even effort.  Understanding human’s susceptibility to sunk costs is important to a range of fields, from behavioral economics to politics. 

    In the article “Sensitivity to 'sunk  costs' in mice, rats, and humans," Sweis et al. discuss the above topic extensively while proving that humans, rats, and mice are all susceptible to sunk costs. Although there have been previous studies confirming the sunk cost effect in humans, much of the research on this bias in animals has shown many inconsistencies. In their study, Sweis et al. used a foraging, or food-searching, task called Restaurant Row to determine whether nonhuman animals are actually sensitive to sunk costs. The set up consisted of a maze, where upon arrival to a “restaurant,” food-restricted mice and rats either choose to wait for that restaurant’s food pellets or move on. The rodents made quick decisions after being trained to know what pitch corresponded to a long or short wait time. A similar task called Web-Surf was used for humans. An important factor in both tasks was the presence or absence of offer zones–where the subjects decide if they want to accept the offer based on the wait time. The researchers collected data for the rodents’ and humans’ quit decisions in the wait zone, where they had already invested some time into the reward. Besides proving the existence of the sunk cost effect in humans and animals, Sweis et al. also found that this effect increases with increasing past investment. This study has greatly contributed to what is now known about sunk costs, and has also allowed for future research on humans’ susceptibility to sunk costs in other areas, such as in individuals with neurological or psychiatric disorders. 

    This can be seen in Fujino et al.’s article, “Impact of past experiences on decision-making in autism spectrum disorder.” In this study, the researchers aim to verify that individuals with autism spectrum disorder (ASD) are less susceptible to sunk costs by comparing their behavior under sunk cost conditions with that of typical development (TD) participants. In order to do this, Fujino et al. utilize an economic task where the participants determine if they want to invest money in a given project based on its cost and likelihood of success. Choosing to invest in the project led to the possibility of the project needing further investment, where the participant would again choose to invest or not. This was considered the sunk cost condition, which helped the researchers determine each group’s susceptibility to sunk costs. Fujino et al. found that there was a significantly larger difference in investments rates between the sunk cost and control conditions for TD participants, compared to ASD participants. They also observed a lower sunk cost effect score for the ASD group. From these findings, the researchers concluded that different decision-making patterns are present in TD and ASD individuals, and that individuals with autism spectrum disorder do experience a lesser effect of sunk costs than people with typical development. 

    In both studies done by Sweis et al. and Fujino et al., the researchers present evidence for the presence of a sunk cost effect on animals, including humans. Both studies indicate humans with typical development to have a high susceptibility to sunk costs during decision-making. The experimental tasks are also very similar, especially regarding the use of a condition that allows subjects to choose to quit the task after already investing in it a first time. Sweis et al. use time as the “investment” in their study, while Fujino et al. use money. Because these two studies look at the effect of sunk costs in different individuals, it leaves future researchers with the goal of providing more evidence for the conservation of sunk cost sensitivity across all animals. Finally, putting the findings from two articles together serves a larger purpose of aiding in the research of decision-making processes in humans with neurological disorders. Since autism is a common disorder, it would be very beneficial to acknowledge the differences in the way these individuals make decisions and behave economically. 

Citations 

Fujino, J., Tei, S., Itahashi, T. et al. Impact of past experiences on decision-making in autism 

        spectrum disorder. Eur Arch Psychiatry Clin Neurosci 270, 1063–1071 (2020).     

        https://doi.org/10.1007/s00406-019-01071-4.

Sweis, Brian M. et al. “Sensitivity to ‘Sunk Costs’ in Mice, Rats, and Humans.” Science 361, 178–181 (2018). doi:10.1126/science.aar8644.