Why are some people willing to put in the hard work needed to succeed while others are content not getting ahead? The answer, claims surprising new research, might be found in an evolving understanding of a brain neurotransmitter called dopamine. Here's what you should know about the chemical that could be making you look lazy:

What is dopamine?
It's a brain neurotransmitter that has a variety of responsibilities. "Our understanding of dopamine has gone through several iterations," study co-author Michael Treadway tells WebMD. It was long known colloquially as "the pleasure chemical," but subsequent studies have also linked it to movement, motivation, memory, emotions, and pain, too, says Ryan Jaslow at CBS News. People who suffer from diseases ranging from Parkinson's to schizophrenia have been known to have a dopamine dysfunction.  

What was the goal of this latest dopamine experiment?
Researchers at Vanderbilt University posited that there's a link between an individual's work ethic and dopamine levels in different brain regions. To test that, the team analyzed 25 healthy men and women ages 19 to 29, using a 20-minute button-pressing exercise and monitoring participants' brain activity. Sometimes participants were given a "hard task," which, for example, asked that they press a keyboard button 100 times in 21 seconds with a nondominant pinky finger. Other times, they were given an "easy task," such as pushing a button 30 times in seven seconds with an index finger. Participants were given cash incentives, ranging from $1 to more than $4, based on a task's difficulty.

And what did they find?
Participants "willing to face long odds and work hard for bigger rewards" had higher dopamine levels in two areas of the brain associated with reward and motivation, says Michael Kelley at Business Insider. That part of the findings, which were published in the Journal of Neuroscience, was expected. Surprisingly, though, the team also discovered that people who were less motivated had higher dopamine levels concentrated in areas involving risk perception and emotion. That means they were more focused on the exercise's cost, like how tired their pinky finger was. 

What does that mean?
What researchers learned could mean that dopamine has "opposite effects in different parts of the brain," says Kelley, which is "surprising because it suggests that more dopamine in a certain part of the brain causes a reduced desire to work." The study authors say this could, in turn, help scientists develop treatments for mental illnesses related to decreased motivation, such as depression or schizophrenia. 

Sources: Business Insider, CBS News, LiveScience, WebMD