Study suggests mice and rats, like humans, make bad choices based on "sunk costs"

A team of researchers at the University of Minnesota discovered that mice and rats tend to make bad decisions. "sunk costs." In their article published in the journal Science the group describes their study and what they found. Sarah Brosnan, of the Georgia State University, offers an article on the work done by the team in the same issue of Review.

Most people know "sunk costs" and some of the behaviors associated with them. An example of a sunk cost is to watch a movie until the end, even if you do not like it, simply because you have already invested a lot of time there. Scientists are studying such behavior as a way to learn more about the human spirit and its functioning. But, perhaps just as important, do other animals have similar traits? If so, this could indicate a biological basis for our behavior. In this new effort, researchers have set up experiments to test whether mice and rats make bad choices simply because they have invested time.

The experiments consisted in setting up a food service for rodents. A rat or mouse would then be introduced into the food court and observed to see how it reacted. To add a measure of the irrecoverable cost, the researchers first trained the rodents to react to different tones. One tone indicated how long they would have to wait for a given treat when they chose it. Another would serve as a countdown, letting them know how long they had to wait once they had made a choice. Rodents also have the option of giving up a choice while they wait to eat something else. The researchers found that rats and mice were waiting for treatment, even though they knew there was a better one, no matter how long they waited in front of them. They also found that the resolution of rodents grew stronger the longer they waited. This, say the researchers, shows that rodents have also made poor choices based on sunk costs.

The researchers also conducted an experiment in which they confronted humans with a choice of videos to watch, and found that volunteers tended to remain resolute while waiting for a video. a video to download once they had chosen to view it. became more resolute the more they waited.

Learn more:
Complete diet for laboratory mice and rats may promote inaccurate test results

More information:
B.M. Sweis et al., "Susceptibility to" sunk costs "in mice, rats, and humans." Science (2018). science.sciencemag.org/cgi/doi … 1126 / science.aar8644

Abstract

Sunk costs are irrecoverable investments that should not influence decisions because decisions should be made based expected future consequences. Animals, whether they are humans or not, can show a sensitivity to sunk costs, but reports from different species are inconsistent. In a time context, an unrecoverable cost sensitivity occurs when an individual resists the end of an activity, even if it seems unproductive, because of the time already invested. In two parallel foraging tasks we designed, we found that mice, rats and humans show similar sensitivities to sunk costs in their decision making. Unexpectedly, the time sensitivity invested only accumulated after an initial decision was made. These results suggest that sensitivity to unrecoverable temporal costs lies in a distinct vulnerability of deliberation processes and that this distinction is present between species.