Psychologists studied individuals with damage to various areas of the prefrontal cortex to better understand how the brain assesses uncertainty and influences rapid decision-making.
You’re at a bus stop, waiting for a bus that feels like it’s never going to arrive. Initially, you hold on to hope that it will come at any moment. However, as the minutes stretch on, uncertainty begins to set in. Should you continue waiting, or would it be wiser to start walking or request a ride instead?
“It’s a common predicament. Should you cling to the belief that the bus is on its way, or is it time to cut your losses and seek alternatives?” says Joe Kable, a psychologist in the School of Arts & Sciences at the University of Pennsylvania. He explains that this situation is not merely about patience; “It’s also about knowing when it’s beneficial to persist and when it’s wiser to move on.”
Kable contrasts two opposing views on perseverance: the idea of “Grit,” emphasized by Penn professor Angela Duckworth, which praises the importance of endurance, versus “Quit” by Penn alum Annie Duke, which discusses the value of knowing when to let go.
In a study published in the Journal of Neuroscience, Kable, along with collaborator Joe McGuire from Boston University and their research team, explore the brain mechanisms behind decisions to persist or quit, analyzing how the brain’s executive functions help determine when to wait or to walk away. Their research focused on individuals with damage to different regions of the prefrontal cortex, which is crucial for executive decision-making, shedding light on how the brain evaluates uncertainty and makes quick decisions.
The findings may have important implications for understanding and potentially treating mental health issues like anxiety, depression, substance use, and addiction, which often involve changes in how rewards are processed and persistence behavior.
Insights from the waiting experience
Kable and his team sought to understand how various areas of the frontal cortex influence decisions to either persist or give up by using a task that mimicked real-life scenarios. In their experiment, participants decided when to “cash out” coins that increased in value over time, with some coins maturing quickly while others took longer, depending on the specific condition set for the task.
“Our goal was to create a scenario where perseverance could sometimes yield rewards, but not always,” explains Kable. In the high-persistence (HP) condition, the maturation times were evenly distributed, making it optimal to wait until the coin reached its highest value. In the limited-persistence condition, the maturation times followed a skewed distribution, meaning if a coin hadn’t matured in the first several seconds, it was wiser to stop waiting. Participants were not informed of these distributions, requiring them to learn from their experiences.
The study included 18 control participants and 31 individuals with brain lesions, categorized by the affected areas of their frontal cortex. Those with damage included individuals with impairments to the ventromedial prefrontal cortex (vmPFC), dorsomedial prefrontal cortex (dmPFC), or the anterior insula (AI), alongside a “frontal control” group with lesions in other frontal areas. By investigating these groups, the researchers aimed to identify the specific roles of different brain regions in making decisions to either persist or quit.
“Studying individuals with these particular lesions allowed us to directly examine how specific parts of the brain influence persistence versus quitting,” says Camilla van Geen, the lead author of the study and a Ph.D. candidate in the Kable Lab.
The results showed that participants with vmPFC damage were less likely to wait overall, especially in the HP condition where persistence was the recommended strategy. “The vmPFC appears essential in gauging the subjective value of waiting,” van Geen notes. “Damage to this area doesn’t just diminish patience; it fundamentally shifts how individuals evaluate whether persistence is justified at all.”
In contrast, participants with lesions in the dmPFC or AI demonstrated a different pattern. They waited about the same length of time across both conditions, failing to discern when persistence was beneficial versus when it was not. “It wasn’t solely a lack of self-control,” Kable clarifies. “These individuals struggled to adapt their strategies based on environmental feedback, especially in situations where quitting was the more advantageous choice.”
Using a computational model, van Geen further examined these decision-making processes and discovered that the vmPFC group had a lower baseline willingness to wait, while those with dmPFC/AI lesions had difficulty learning from their quit trials.
A changing view on rewards
“This is not merely a question of self-control or being impulsive; it relates to how our brains assess value and adapt in real-time to determine when waiting is worthwhile,” van Geen states.
A surprising result was that individuals with lesions in the lateral prefrontal cortex, an area often linked to self-control, performed equally well as healthy participants. This finding suggests that while the vmPFC helps evaluate the baseline value of waiting and the dmPFC and AI assist in learning from feedback, the lateral prefrontal cortex may not be as integral to persistence as previously believed.
“We often perceive persistence as positive and quitting as a failure,” van Geen remarks. “However, they are really interrelated aspects. Each requires intricate mental calculations, and either can be the correct choice based on the context.”
Looking ahead, the researchers plan to investigate neurotransmitters such as dopamine and serotonin to gain deeper insight into how these systems affect persistence. “We’ve conducted a study where participants are administered drugs that enhance these systems to observe how it influences their willingness to wait,” Kable mentions. “Initial results hint that serotonin has a particularly noteworthy role, but we are still analyzing the data.”
Future studies will also explore the interactions between brain regions and neurotransmitter systems. “Do these systems interact with each other, or do they function independently? This is one of the significant questions we aim to address next,” Kable concludes.
Joseph W. Kable is the Jean-Marie Kneeley President’s Distinguished Professor of Psychology at the University of Pennsylvania’s School of Arts & Sciences.
Camilla van Geen is a Ph.D. candidate in Penn Arts & Sciences.
Other contributors include Yixin Chen from Boston University, Rebecca Kazinka from the University of Minnesota, and Avinash R Vaidya from the NIDA Intramural Research Program.
This research was supported by the National Institutes of Health (grants R01-DA029149, F32-DA030870, and R21-MH124095 and award ZIA DA000642), as well as by the National Science Foundation (Grant BCS-1755757).
