Emotion in animals teeth in aggressive action. A domestic dog's simple tail wag may be used in subtly different ways to convey many meanings as illustrated in Darwin's "The Expression of the Emotions in Man and Animals" published in 1872. Evidence for emotions in animals has been primarily anecdotal, from individuals who interact with pets or captive animals on a regular basis. However, critics of animals having emotions often suggest that anthropomorphism is a motivating factor in the interpretation of the observed behaviours. Much of the debate is caused by the difficulty in defining emotions and the cognitive requirements thought necessary for animals
The Expression of the Emotions in Man and Animals induce directly opposing movements. Finally, he discusses a "direct action of the nervous system", in which an overflow of emotion is widely discharged, producing more generally expressed emotions. This is followed by a section (three more chapters) on modes of emotional expression peculiar to particular species, including man. He then moves on to the main argument with his characteristic approach of astonishingly widespread and detailed observations. Chapter 7 discusses "low spirits", including anxiety, grief, dejection and despair; and the contrasting Chapter 8 "high spirits" with joy, love, tender feelings and devotion. Subsequent chapters include considerations of "reflection and meditation" (associated