Editors: Contents embargoed for use at 2 p.m. EST on Thursday, Nov. 4. For those who have wondered why they like or dislike certain things, or how they decide what to order from a menu, a team of researchers at the University of Colorado at Boulder says it's dopamine. A CU-Boulder team studying Parkinson's disease patients found strong evidence that dopamine in the brain plays a key role in how people implicitly learn to make choices that lead to good outcomes, while avoiding bad ones.