Edgeworth was only engaging in conjecture, but in 2001, Brian Knutson, a Stanford University professor, arranged an experiment that would use functional magnetic resonance imaging (fMRI) to do just that. Knutson and his colleagues at the National Institutes of Health asked participants attached to a brain scanner to watch a screen as colored shapes appeared. He told them that if they pressed a button when certain shapes flashed onscreen, they would earn a cash reward. Other shapes offered no opportunity for "earning" money. All the participants later rated, on a four-point scale, how they felt when viewing different shapes and colors. They said that seeing the shapes associated with the reward made them happy—and their neural firing patterns agreed, with the fMRI displaying increased bloodflow to a brain region associated with reward.