In today’s Academic Minute, Dr. David Zald of Vanderbilt University reveals why some people are more willing to go the extra mile for a potential reward.
David Zald is an associate professor of psychology and psychiatry at Vanderbilt University and a fellow of the Vanderbilt Brain Institute. He is also director of the Affective Neuroscience Lab, a facility working to understand the neural and neuropharmacological systems involved in emotion and motivation, and the relationship of individual differences in these circuits to personality and psychopathology. He holds a Ph.D. from the University of Minnesota.
Dr. David Zald – Brain Chemistry and Work Ethic
Some people work harder than others. Some individuals are so motivated by potential rewards that they will expend effort even if the odds of success are low, while others take a more economical attitude towards expending energy. My lab became interested in the decision processes involved in expending energy in the context of depression, during which people are often unmotivated to work.
We created a task called the Effort Expenditure for Rewards Task, or Effort for short, which measures how much individuals are willing to work for rewards. During each trial, participants must choose whether to do an easy task for a dollar or a hard task to get a larger amount of money. The amount of money for the high reward and the probability of receiving the reward changes on each trial. People naturally choose the hard task more frequently when it has substantially higher rewards than the easy task. Similarly people are more like to do the hard task when the probability of getting the reward increases.
We have been particularly interested in the impact of the neurotransmitter dopamine on decisions about effort. Studies in rats indicate that if you deplete dopamine, the rats decrease their willingness to work for food. In humans, we have found that if you cause someone to increase dopamine release, for instance by giving them amphetamine, they will select the harder task more often than if they are given a placebo, especially on trials in which the probability of getting rewarded is low.
Using positron emission tomography, which lets us safely measure levels of dopamine receptors and dopamine release in humans, we have recently found that individual differences in dopamine release in specific areas of the brain are predictive of people’s willingness to work for rewards on the Effort. Although we often think of the willingness to work as a moral virtue, these findings suggest that some of our differences in work ethic relate to basic features of neurochemistry.