Brain imaging suggests impulsive people don’t think about the reward they’ll get for waiting, whereas patient people seem to enjoy it.
“Activity in one part of the brain, the anterior prefrontal cortex , seems to show whether you’re getting pleasure from thinking about the future reward you are about to receive,” explains study co-author Todd Braver, professor of psychology in at Washington University in St. Louis. “People can relate to this idea that when you know something good is coming, just that waiting can feel pleasurable.”
The study, which appears in the Journal of Neuroscience, aimed to examine what happens in the brain as people wait for a reward, especially whether people characterized as “impulsive” would show different brain responses than those considered “patient.”
Unlike previous research on delayed gratification that had people choose between hypothetical rewards of money over long delays (e.g., $500 now or $1,000 a year from now), this study presented participants with real rewards of squirts of juice that they chose to receive either immediately or after a delay of up to a minute.
“It’s kind of funny because we treated the people in our study like researchers that work with animals do, and we actually squirted juice into their mouths,” Braver says.
Results show that a brain region called the ventral striatum (VS) ramped up its activity in impulsive people as they got closer and closer to receiving their delayed reward. The VS activity of patient people, on the other hand, stayed more constant.
The researchers interpreted these different brain responses to mean that impulsive people initially did not find the prospect of waiting for a reward very appealing. However, as they approached the time they’d receive that reward, they became more excited and their VS reflected that excitement.
“This gradual increase may reflect impatience or excessive anticipation of the upcoming reward in impulsive individuals,” says lead author Koji Jimura, a former postdoctoral scholar in Braver’s lab. This was unlike patient people, who were likely content with waiting for the reward from the start, as no changes in VS activity were observed for them.
The most novel finding of the study concerned the anterior prefrontal cortex (aPFC). This is the part of the brain that helps you think about the future. There, the researchers found that the patient people heightened activity in the aPFC when they first started waiting for they reward, which then decreased as the time to receive the reward approached. Impulsive people didn’t show this brain activity pattern.
“The aPFC appears to allow you to create a mental simulation of the future. It helps you consider what it’ll be like getting the future reward. In this way, you can get access to the utility and satisfaction in the present,” says Braver.
By thinking about the future reward, patient people were able to gain what economists call “anticipatory utility.” While their reward was far away in time, they were giddy with anticipation in the present.
Conversely, impulsive people weren’t thinking beyond the present and so did not feel pleasure when they were told they had to wait. Their excitement built only as they got closer to receiving their reward.
Overall this study suggests that people may be impulsive because they do not or cannot imagine the future, so they prefer rewards right away. This research could be useful for assessing the effects of clinical treatments for impulsivity problems, which can lead to issues such as problem gambling and substance abuse disorders.
A similar brain imaging approach as was used in this study could allow clinicians to track the effects of an intervention on changes not only in impulsive behavior but also changes in patients’ brain responses.
“One possible treatment approach could be to enhance mental functions in aPFC, a brain region well-known to be associated with cognitive control,” says Jimura, now a research associate professor at Tokyo Institute of Technology. By increasing cognitive control, impulsive patients could learn to reject their immediate impulses.
Impulsivity occurs not only in a clinical setting but also every day in our own lives. Applying his research to his personal life, Braver says, “When I’m successful at achieving long-term goals it’s from explicitly trying to activate that goal and imagining each decision as helping me achieve it, to keep me on track.”