"Until recently, scientists assumed that the neural reward pathways, which act as high-speed Internet connections to the pleasure centers of the brain, responded to what people like," Read Montague of Baylor College of Medicine explains. "However, when we tested this idea in brain scanning experiments, we found that reward pathways responded much more strongly to the unexpectedness of stimuli instead of their pleasurable effects." In other words, the subjects' brains were more active when they were exposed to the unanticipated.
"We find that so-called pleasure centers in the brain do not react equally to any pleasurable substance, but instead react more strongly when the pleasures are unexpected," Emory neuroscientist Gregory Berns adds. "This means that the brain finds unexpected pleasures more rewarding than expected ones, and it may have little to do with what people say they like."