Paper out in the Journal of Neuroscience (it's open access - anyone can download the paper) with my UCL colleagues Nikolina Skandali, Peter Dayan, and Ray Dolan.
We report the results of a pharmacology experiment in which subjects made choices between safe and risky options and were repeatedly asked 'how happy are you at this moment?' After boosting dopamine levels with the drug levodopa, a drug commonly used to treat Parkinson's disease, subjects were more likely to take risks to try to get bigger rewards and they also felt happier after they received some of those rewards. These results might help explain why some people receiving dopaminergic treatment can develop gambling problems. Boosting dopamine levels may make people think that some rewards are better than they actually are, helping to clarify the role of dopamine in happiness.
The paper can also be downloaded here. My research is supported by the Max Planck Society and the Wellcome Trust.