"Intuition is fast, based on pattern matching," explains John Allman, Ph.D., head of a laboratory at the California Institute of Technology that focuses on brain evolution. "Our brains are constantly comparing current experience with the past, trying to find a fit so that we can make a quick decision. When we find a match, often in a fraction of a second, our intuition boils down a lot of experience into a simple, visceral metric: I feel good about this or not," Allman says.