July 13, 2018
University of Minnesota
Medical School
New research has shown that
mice, rats, and humans all commit the sunk cost fallacy.
The behavior of people who
remain committed to a choice, even when it is clear that an alternate choice
would be a better option, has been a perplexing phenomenon to psychologists and
economists. For example, people will continue to wait in the slow line at a
grocery store, stick out an unhealthy relationship, or refuse to abandon an
expensive, wasteful project -- all because such individuals have already
invested time, effort, or money. This well-known cognitive phenomenon termed
the "sunk cost fallacy" has long been considered a problem unique to
humans. New research has discovered that humans are not the only species that
share these economically irrational flaws.
New research from the
University of Minnesota published in the journal Science discovered
that mice, rats, and humans all commit the sunk cost fallacy.
"The key to this research
was that all three species learned to play the same economic game," says
Brian Sweis, the paper's lead author, an MD/PhD student at the University of
Minnesota. Mice and rats spent time from a limited budget foraging for flavored
food pieces while humans similarly spent a limited time budget foraging for
what humans these days seek -- entertaining videos on the web.
Rats and mice ran around a
maze that contained four food-delivery-locations ("restaurants"). On
entry into each restaurant, the animal was informed of how long it would be
before food would be delivered by an auditory tone. They had one hour to gather
food and thus each entry meant they had to answer a question like, "Am I
willing to spend 20 seconds from my time budget waiting for my cherry-flavored
food pellet?" with a delay lasting anywhere from 1 to 30 seconds.
Similarly, humans saw a series
of web galleries and were informed of the delay by a download bar. This meant
humans had to answer an equivalent question: "Am I willing to spend 20
seconds from my time budget waiting for my kitten video?" In this way,
each subject from each species revealed their own subjective preferences for
individual food flavors or video galleries.
In this task, every entry
required two decisions, a first decision when the delay was revealed, but did
not count down, and then a second decision if the offer was accepted when
subjects could quit and change their minds during the countdown. Remarkably,
the authors found that all three species become more reluctant to quit the
longer they waited -- demonstrating the sunk cost fallacy.
Strikingly, subjects hesitated
before accepting or rejecting offers during the initial decision before the
countdown. "It's as if they knew they didn't want to get in line until
they were sure," says Sweis. Even more surprising, neither mice, rats, nor
humans took into account the sunk costs spent while deliberating. This suggests
that the process of deliberation and the process of changing one's mind after
an initial commitment depend on different economic factors, and that these
factors are conserved across species.
"This project depended on
the collaborative nature of science today," says senior author David
Redish, a professor in the University of Minnesota Medical School's
Neuroscience Department. "This was a collaboration between three
laboratories and required working back and forth to ensure that we could ask
similar questions across different species on these parallel tasks."
As such, this project builds
on a number of breakthrough discoveries recently published by these
laboratories, which find that mice, rats, and humans use similar neural systems
to make these different types of decisions, that mice and rats also show regret
after making mistakes, and that even mice can learn to avoid those mistakes by
deliberating first, as revealed in a recent paper by these authors in PLOS
Biology.
"These tasks reveal
complex decision processes underlying the conflict between really wanting
something on the one hand versus knowing better on the other," says Sweis.
"This is a conflict
between different neural decision systems, and that means we can separately
manipulate those systems," says Redish.
In other publications recently
appearing in Nature Communicationsand the Proceedings of the National
Academy of Sciences, these authors have found that both the effect of different
drugs (cocaine, morphine) and different changes to neural circuits affect these
two systems differently, which suggests that different forms of addiction would
likely benefit from individualized treatments tailored to dysfunctions in
distinct brain circuits.
"Decisions depend on
neural circuits, which means that manipulating those circuits changes the
decision process," says Mark Thomas, another of the study's senior authors
and a professor in the Medical School's Neuroscience Department.
"There was a day when we
asked ourselves, 'Rats forage for food, what do undergrads forage for?'"
remembers author Samantha Abram, now a postdoctoral psychology fellow at the
San Francisco VA Medical Center, who led the human component as a graduate
student in the University of Minnesota Clinical Science and Psychopathology
Research Program with her advisor Angus MacDonald, a professor in the
Psychology Department of the University of Minnesota College of Liberal Arts.
By having all three species
play the same economic game, these authors have revealed a new insight into how
different parts of the brain make different types of decisions and that there
is an evolutionary history to the flaws that make us human.
Story Source:
Materials provided
by University of
Minnesota Medical School. Note: Content may be edited for style and
length.
Journal References:
Brian M. Sweis, Samantha V.
Abram, Brandy J. Schmidt, Kelsey D. Seeland, Angus W. Macdonald Iii, Mark J.
Thomas, A. David Redish. Sensitivity to “sunk costs” in mice, rats, and
humans. Science, 13 Jul 2018: Vol. 361, Issue 6398, pp. 178-181 DOI: 10.1126/science.aar8644
Brian M. Sweis, Mark J.
Thomas, A. David Redish. Mice learn to avoid regret. PLOS Biology,
2018; 16 (6): e2005853 DOI: 10.1371/journal.pbio.2005853
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