Dopamine impacts your willingness to work

Jeremy Teaford/Vanderbilt University

Slacker or go-getter?

Everyone knows that people vary substantially in how hard they are willing to work, but the origin of these individual differences in the brain remains a mystery.

Now the veil has been pushed back by a new brain imaging study that has found an individual’s willingness to work hard to earn money is strongly influenced by the chemistry in three specific areas of the brain. In addition to shedding new light on how the brain works, the research could have important implications for the treatment of attention-deficit disorder, depression, schizophrenia and other forms of mental illness characterized by decreased motivation.

The study was published May 2 in the Journal of Neuroscience and was performed by a team of Vanderbilt scientists including postdoctoral student Michael Treadway and Professor of Psychology David Zald.

Using a brain mapping technique called positron emission tomography (PET scan), the researchers found that “go-getters” who are willing to work hard for rewards had higher release of the neurotransmitter dopamine in areas of the brain known to play an important role in reward and motivation, the striatum and ventromedial prefrontal cortex. On the other hand, “slackers” who are less willing to work hard for a reward had high dopamine levels in another brain area that plays a role in emotion and risk perception, the anterior insula.

Dopamine levels were undoubtedly running high as researchers Michael Treadway, left, and David Zald mock-arm-wrestled. (Steve Green/Vanderbilt )

“Past studies in rats have shown that dopamine is crucial for reward motivation,” said Treadway, “but this study provides new information about how dopamine determines individual differences in the behavior of human reward-seekers.”

High levels of dopamine activity, shown in blue and green, were found in the bilateral insula in the brains of "slackers." (Courtesy of Zald Lab)

The role of dopamine in the anterior insula came as a complete surprise to the researchers. The finding was unexpected because it suggests that more dopamine in the insula is associated with a reduced desire to work, even when it means earning less money. The fact that dopamine can have opposing effects in different parts of the brain complicates the picture regarding the use of psychotropic medications that affect dopamine levels for the treatment of attention-deficit disorder, depression and schizophrenia because it calls into question the general assumption that these dopaminergic drugs have the same effect throughout the brain.

The study was conducted with 25 healthy volunteers (52 percent female) ranging in age from 18 to 29. To determine their willingness to work for a monetary reward, the participants were asked to perform a button-pushing task. First, they were asked to select either an easy or a hard button-pushing task. Easy tasks earned $1 while the reward for hard tasks ranged up to $4. Once they made their selection, they were told they had a high, medium or low probability of getting the reward. Individual tasks lasted for about 30 seconds and participants were asked to perform them repeatedly for about 20 minutes.

Schematic of the button-pushing task used in the experiment. (Courtesy of Zald Lab)

“At this point, we don’t have any data proving that this 20-minute snippet of behavior corresponds to an individual’s long-term achievement,” said Zald, “but if it does measure a trait variable such as an individual’s willingness to expend effort to obtain long-term goals, it will be extremely valuable.”

High levels of dopamine activity, shown in orange and yellow, were found in the striatum (center) and ventromedial prefrontal cortex (right) in the brains of "go getters." (Courtesy of Zald Lab)

The research is part of a larger project designed to search for objective measures for depression and other psychological disorders where motivation is reduced. “Right now our diagnoses for these disorders is often fuzzy and based on subjective self-report of symptoms,” said Zald. “Imagine how valuable it would be if we had an objective test that could tell whether a patient was suffering from a deficit or abnormality in an underlying neural system. With objective measures we could treat the underlying conditions instead of the symptoms.”

Further research is needed to examine whether similar individual differences in dopamine levels help explain the altered motivation seen in forms of mental illness such as depression and addiction. Additional research is under way to examine how medications specifically impact these motivational systems.

Robert Kessler, professor of radiology and radiological sciences, Ronald Cowan, associate professor of psychiatry, Joshua Buckholtz, assistant professor of psychology at Harvard, Neil Woodward, assistant professor of psychology, Rui Li, senior research specialist of radiology and radiological sciences, Sib Ansari, associate of radiology and radiological sciences, Ronald Baldwin, research associate professor of radiology and radiological sciences, and research assistant Ashley Schwartzman also contributed to the study. The National Institute of Drug Abuse funded the research.

David Salisbury :(615) 322-NEWS

View Comments (10)

    • Cute answer, but a little glib. Trust me, if you have one of these disorders, all the material motivation in the world won't get you out of bed. It's not a character flaw, it's a brain disorder -- if you could just get over it with a little more cash waved in your face, they wouldn't be putting so much money into treating it.

      • I don't disagree, but everything results from brain activity. Where do you draw the line between character flaw and brain disorder?

      • I think reduced motivation is connected with decision making and mental energy (will power) http://www.nytimes.com/2011/08/21/magazine/do-you-suffer-from-decision-fatigue.html?pagewanted=all

        People burn out when their efforts don't bring them what they want (positive feedback). And what they want is signified at the physiological level by dopamine release.

        On the other hand, transcendent Will is unconditional because it is itself the ultimate cause of everything. This part of consciousness is beyond reason. I think this is why it is so difficult to find out what we really want, not what we think we want. That's what being oneself means. http://www.stevepavlina.com/blog/2005/01/how-to-discover-your-life-purpose-in-about-20-minutes/

        But that requires focusing — something that people with attention deficit can't do well.

        What do you think?

  • Nick,

    Thanks for your comment. The article information is as follows:

    Michael T. Treadway, Joshua W. Buckholtz, Ronald L. Cowan, Neil D. Woodward,Rui Li, M. Sib Ansari, Ronald M. Baldwin, Ashley N. Schwartzman, Robert M. Kessler, and David H. Zald
    Dopaminergic Mechanisms of Individual Differences in Human Effort-Based Decision-Making; The Journal of Neuroscience, 2 May 2012, 32(18):6170-6176;doi:10.1523/JNEUROSCI.6459-11.2012

  • "Slacker or Go-getter?"??  Look around you.  Every other creature bigger than a mouse likes to take it easy a lot of the time. Are you saying that people who feel the same way are slackers? Are sick?  I'd say it's the hyperactive that are abnormal - fair play to them, they've given us medicine, microwaves and colour television, but that doesn't mean that everyone and everything else are the odd ones out.

  • What is the region that can produce dopamine? Is it pituitary gland only or there are other regions as well?

  • We must always rely on looking at a person's thoughts and behaviors, not scans.

    Expecting these scans to show us anything other than general tendencies is ridiculous. If a person's brain scan looks depressed but in their daily life their thoughts are happy and they are happy or at least content with their life then there isn't a problem. But maybe then scientists could offer money to involve the person in further studies to see why that person isn't depressed in spite of their brain chemistry.

    Similarly, we shouldn't be waving away patients because "the scan says you're fine." though maybe if the scan looks normal ordinary treatments would not work.