Would someone choose $20 today or $50 next month? A study suggests that brain structure contains some information about how people make these trade-offs, although it cannot determine how any individual will behave.
Researchers analyzed brain scans and decision-making assessments from 146 college-aged adults, whose average age was about 22.6. They used machine-learning models to estimate participants’ delay discounting: the extent to which a person places less value on a reward the longer they have to wait for it. A preference for a smaller, immediate reward over a larger, delayed one is commonly used as a behavioral measure of impulsive decision-making.
Published in JAMA Psychiatry, the study found that models based on the volumes of selected brain regions could predict participants’ delay-discounting scores with moderate accuracy. The white matter model accounted for an average of 22% of the variation in scores, while the gray matter model accounted for 19% across the tests. The researchers said this indicates that brain structure contains relevant information, but it explains only part of the differences between people.
Two regions in the right hemisphere appeared in both models: the accumbens area, involved in reward processing and motivation, and the frontal pole, associated with planning and weighing longer-term consequences. Other selected regions included areas involved in sensory and visual processing, as well as frontal regions linked to self-control.
The white matter model performed somewhat better than the gray matter model. The researchers said this points to the potential importance of considering both types of brain tissue when studying decision-making. However, their white matter measurements reflected regional tissue volume, not the microscopic condition or organization of nerve fibers.
The authors describe the work as an initial proof of concept. The models were tested on held-out portions of the same dataset, but not on an independent group. The study also involved a relatively small sample of young adults, and each test group included about 29 participants. The researchers cautioned that the results may change when tested in larger and more varied populations.
Because the study measured brain anatomy and decision-making at a single point in time, it cannot show whether structural differences influence people’s choices or whether behavior and life experiences shape brain structure. Nor do the findings mean that a scan can determine how someone will act: delay discounting can vary with circumstances and may change through learning or intervention.
The researchers say future work should test the models in larger, independent groups and combine structural scans with other imaging methods. They also hope to study clinical populations, including people with substance use disorders, eating disorders and ADHD, while emphasizing that any clinical use would require further validation.
Sources: PsyPost.