Dolphins are capable of imitation and memorization; they demonstrate foresight, learn from observation, communicate experience, solve complex problems, perform elaborate tasks, and learn multiple procedures simultaneously. Their so-called training is in fact a discipline structured around play, using their natural behavior as the basis for involved maneuvers; they appear to perform primarily for their own enjoyment. In situations of great stress in captivity they have been known to commit suicide by starvation, battering against walls, or drowning. There are many reports of dolphins rescuing people from drowning