From Ahab relentlessly pursuing Moby Dick to Wile E. Coyote's futile chase of the Road Runner, these scenarios share a common thread with learning Latin, walking over hot coals, enduring long lines for boba tea, and splurging on luxury indulgences. They all exemplify the concept of “sunk costs” in economics—the irretrievable investment of time, money, effort, or suffering into something.
A study delving into this phenomenon is documented in the journal Neuron.
This recognizable phenomenon often influences our behavior in seemingly irrational ways. We all succumb to it.
Consider my experience with the glacial-blue '64 stick-shift Volvo station wagon adorned with patriotic Colorado U.S. Bicentennial plates and a trio of miniature bowling trophies for hood ornaments. Fondly nicknamed “the Bowlvo,” this vehicle was akin to a deteriorating piece of overcooked chicken. Despite its shortcomings, I found myself willing to go to great lengths—or at least the end of my rope—to keep it operational. It's a peculiar aspect of human nature, where we attach greater value to something when we've invested considerable effort, whether it be time, money, or perseverance, into obtaining or maintaining it.
Neuroscientists are actively unraveling the mysteries behind this tendency, attempting to understand why we inherently ascribe higher value to entities that involve significant “sweat equity”—the toil we undergo to secure, or in my case, preserve a particular reward.
Assistant Professor of Psychiatry and Behavioral Science, Neir Eshel, MD, Ph.D., points out that our decision-making is often flawed, driven by our investment in something even when the likelihood of gaining an objective advantage is nonexistent. This tendency isn't exclusive to humans; it's observed across the animal kingdom.
Dopamine, the brain chemical associated with pleasure, learning, and habit formation, plays a crucial role in this behavior. Eshel emphasizes the distinction between wanting and liking, highlighting that one can desire something intensely even if they don't particularly enjoy it, and vice versa.
In collaboration with his postdoctoral adviser, Rob Malenka, MD, Ph.D., the Nancy Friend Pritzker Professor in Psychiatry and the Behavioral Sciences, and other Stanford Medicine colleagues, Eshel conducted experiments to delve into the realms of wanting versus liking. The focus was on understanding the impact of dopamine secretion in the brain on these states.
The team explored how much an animal enjoys something (measured by its consumption when the item is cost-free) and how much it desires something (evaluated by how consumption is influenced by the cost associated with obtaining it).
In unraveling the complex interplay of wanting and liking, these experiments shed light on the role of dopamine in driving our decisions, offering insights into the mechanisms that underlie our seemingly irrational behaviors.
The dopamine connection
During their study, the research team uncovered a potential neural mechanism behind the psychological phenomenon of valuing rewards more when greater effort is exerted to obtain them. They identified a significant influence on dopamine release in the striatum, providing a possible neural explanation for the concept of sunk cost.
Assistant Professor Neir Eshel highlighted the role of dopamine in this phenomenon, suggesting it may be the neural basis for our tendency to overvalue investments in rewards.
In their mouse study, the researchers defined “cost” as the effort required for the mice to obtain a reward, either by poking their noses into a hole a varying number of times or risking mild to moderate foot shocks. The rewards included sugar water or direct stimulation of dopamine release in the striatum.
The scientists first measured “cost-free consumption,” determining how much a mouse would consume until satiated in a situation where the reward was easily accessible. This provided insights into how much the mouse “liked” the reward. Subsequently, they systematically increased the acquisition cost by raising the number of nose-pokes or the intensity of electric shocks required.
Surprisingly, the researchers found that not only did striatal dopamine release correlate with the size of the reward, but it also increased with the rising cost of obtaining the reward. This biochemical connection revealed a neural basis for the concept of sunk cost, linking the effort invested in obtaining a reward to the release of dopamine in the striatum.
Sunk cost and survival
The evolutionary rationale behind valuing something due to sunk costs, deemed aberrant decision-making by economists, raises intriguing questions. Neir Eshel proposes a compelling idea: in an environment with limited resources, where rewards often follow strenuous efforts, high dopamine secretion may have evolved as a motivational mechanism.
“In an environment with limited resources (as most are), when we typically get rewarded only after really hard work, we may need high dopamine secretion to get us to do it again,” suggests Eshel. He posits that dopamine, by reinforcing previous behaviors, could be linked to the concept of sunk costs. The observed dopamine release may serve as an evolutionary adaptation, enabling individuals to overcome steep costs in the pursuit of rewards in the future. This perspective sheds light on the intricate interplay between neurotransmitters and decision-making in the context of resource-constrained environments.