Dopamine Makes Us Less Tolerant Of Inequality

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Justine Alford

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1332 Dopamine Makes Us Less Tolerant Of Inequality
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Using a drug to alter the brain chemistry of volunteers, scientists have demonstrated it is possible to make people more sensitive to inequality and thus more likely to engage in actions that benefit others, or prosocial behaviors. The idea behind this intriguing study is not to attempt to make people of the world more philanthropic through popping pills, but rather to further our knowledge of certain mental illnesses that are associated with chemical imbalances in the brain, such as schizophrenia or addiction. Ultimately, they hope, research like this could lead to improved ways to diagnose such conditions, and possibly even treatments.

“Our study shows how studying basic scientific questions about human nature can, in fact, provide important insights into diagnosis and treatment of social dysfunctions,” study author Ming Hsu said in a news release.


The belief that all people should be equal, or egalitarianism, is a powerful driver in the promotion of prosocial behaviors, which are positive actions designed to help others or society as a whole. In recent years, evidence has mounted to suggest an association between this type of behavior and the chemical messenger dopamine, which is involved in the control of movement, emotional response and the ability to experience pleasure and pain. However, studies have been correlative and the specific role of this hormone remained hazy.

To find out more about whether dopamine can indeed encourage egalitarian tendencies in humans, scientists from UC Berkeley and UC San Francisco decided to investigate the effects of altering the levels of this chemical in the brain on behavior. To do this, they enlisted the help of an FDA-approved drug called tolcapone, which is used to treat people with Parkinson’s. Tolcapone acts by prolonging the effects of dopamine, which is known to be associated with reward and motivation in one particular brain region: the prefrontal cortex.

As described in Current Biology, on two separate occasions, 35 participants were either given a dummy pill or tolcapone and were then asked to play an easy economic game in which they divided money between themselves and an anonymous participant. The experiment was double-blinded, meaning that neither the researchers nor the participants knew which pill they were taking.

Interestingly, the researchers observed that after taking tolcapone, volunteers acted in a more egalitarian manner towards the strangers than after taking the placebo, splitting the money in a fairer way. Furthermore, computer modelling of their behaviors revealed that tolcapone made people more sensitive to inequity, or a lack of fairness.


“We typically think of fair-mindedness as a stable characteristic, part of one’s personality,” said Hsu. “Our study doesn’t reject this notion, but it does show how that trait can be systematically affected by targeting specific neurochemical pathways in the human brain.”

Since earlier studies have indicated that inequity is evaluated in the prefrontal cortex, and dopamine is known to act on this region, the researchers believe these findings represent progress towards understanding where prosocial behaviors originate in the brain.

“Studies in the past decade have shed light on the neural circuits that govern how we behave in social situations,” lead author Ignacio Sáez said in a statement. “What we show here is one brain ‘switch’ we can affect.” 


  • tag
  • dopamine,

  • parkinson's,

  • prosocial behavior,

  • egalitarianism,

  • prefrontal cortex