The pebble was tossed into the water by Charles Darwin in 1872 when he declared in his book The Expression of the Emotions in Man and Animals that humans are not the only members of the animal kingdom that experience a wide array of emotions and feelings. Despite the reputation of the renowned biologist, the ripples that this tiny rock generated went largely unappreciated at the time. In fact, these ripples remained quite small until the middle of the next century. In the past 40 years alone, the rapid advances of research in the cognitive sciences and related fields have caused the ripples in the water to swell to thunderous Waikiki-size waves
