Happy New Year! It's 2013 and you've vowed to cut sweets out of your diet. Despite your desire for a trimmer body, the sight of cupcakes in a café window overpowers your good intentions. You cannot resist the small, sweet reward even though the larger, delayed reward of a healthier body is ultimately more desirable.
What leads some of us to give in to our immediate urges, while others are able to endure the wait for bigger and better outcomes? Neuroeconomists are investigating the brain to answer this question. They are interested in comparing the brain activity of individuals who act impulsively--those who choose rewards now over later--to that of patient folks.
Traditionally, the assumption of researchers in this field, and the related field ofbehavioral economics, has been that impulsive people choose immediate rewards simply because they dislike waiting. In these prior studies, when presented with a hypothetical choice between, say, $50 now or $100 in a year, impulsive individuals went for the $50.  Additionally, they showed a greater brain response to the immediate $50 reward--in the part of the brain that represents how much you are enjoying a reward (the ventral striatum)--than did patient people. Researchers interpreted this brain response as the impulsive individuals' preference for immediacy. So while impulsive individuals would claim "carpe diem" and "strike while the iron is hot" as their life mantras, the less quoted "carpent tua poma nepotes" and "good things come to those who wait" are patient individuals' words to live by.
However, impulsivity may not simply be due to how long people are willing to wait for gratification. A recent study by a team of researchers at Washington University in St. Louis found that when people waited for a reward, patient people were seen--through the lens of a functional magnetic resonance imaging (fMRI) machine--imagining the future. In more patient people, the researchers observed increased activity in the region of the brain that helps you think about the future (the anterior prefrontal cortex). The patient individuals, it seems, devoted more energy to imagining receiving their reward later.
What sets this Washington University study apart from previous studies is that researchers have never before focused on the brain responses of individuals after they make a decision and are waiting for their reward.  Instead, researchers have typically measured brain activity while people are making their choices. Prior researchers likely disregarded the waiting period because their studies used hypothetical rewards over long delays. Because people weren't actually waiting in real time to receive a real reward, the researchers could not monitor the brain during this waiting period. This new study presented people with real rewards in the form of squirts of juice either immediately or at a delay of up to a minute. In fact, the researchers squirted the juice straight into the mouths of study subjects, in much the same way that animals have been rewarded in similar studies.
This future thinking, which is associated with the anterior prefrontal cortex (aPFC), has also been found in neuropsychological studies that focus on two different, but related phenomena: prospective memory--remembering to do something in the future, like fill up your gas tank on the way home from work--and episodic future thought--thinking about the future, such as imagining what you'll cook for dinner later tonight. Now, one more phenomenon can be added to the list of contexts in which people imagine a future outcome and activate their aPFC: imagining future rewards.