Trying to quit something such as smoking, drinking or eating junk food can be a difficult task. New research sheds some light on why the human brain has difficulty letting go of previous addictions.
According to a press release issued by Johns Hopkins University, a new study demonstrated for the first time that when people encounter something associated with a past reward, their brains flood with dopamine, even if they aren’t expecting a reward and don’t know they’re paying attention to it. Dopamine is a brain chemical proven to be released when people receive rewards.
According to the study, researchers asked 20 participants to find the red and green objects on a screen of many different colored objects, and rewarded them with $1.50 for finding the red and 25 cents for finding the green.
The following day, researchers asked participants to find shapes on a screen, the colors of which were irrelevant, while conducting brain scans. Though there was no reward involved, whenever a red object appeared on the screen, participants focused on it. Brain scans showed that upon seeing the red object, a particular part of the participants’ brain involved in attention filled with dopamine.
"I could choose healthy food or unhealthy food, but my attention keeps being drawn to fettuccini Alfredo," says senior author Susan M. Courtney in the press release. Courtney is a professor in the Department of Psychological and Brain Sciences at John Hopkins. She adds:
"What we tend to look at, think about and pay attention to is whatever we've done in the past that was rewarded."
The study showed that though participants did eventually find the shape they were looking for, they were slow in doing so because the red distracted them. The most distracted participants had the highest dopamine levels being released, and the less distracted participants appeared to be suppressing any release of dopamine.
"What's surprising here is people are not getting rewarded and not expecting a reward," says Courtney in the press release. "There's something about past reward association that's still causing a dopamine release. That stimulus has become incorporated into the reward system."
The full study will be published in Current Biology. It was funded in part by the National Institutes of Health.
The authors disclosed no conflicts of interest.