The Expression of the Emotions in Man and Animals

is a scientific work published in 1872. Darwin's third major evolution ary study examines the biological origins of human emotional behavior- from smiling and frowning to blushing and surprise. Challenging tradi tional spiritual explanations, Darwin traces these expressions to animal be havior andarguesfor theiruniversalnature across all humancultures. Using innovative methods including questionnaires, psychological experiments, andpioneeringphotography, Darwinestablishesconnectionsbetweenmen tal states and physical movement, forming what some consider the founda tion of modern scientific psychology

the three chief principles stated-The first principle-Serviceable actions become habitual in association with certain states of the mind, and are performed whether or not of service in each particular case-The force of habit-Inheritance-Associatedhabitualmovementsinman-Reflexactions- Passage of habits into reflex actions-Associated habitual movements in the lower animals-Concluding remarks.

will begin by giving the three Principles, which appear to me to account for most of the expressions and gestures involuntarily used by man and the lower animals, undertheinfluence ofvariousemotionsandsensations.[101] I arrived, however, at these three Principles only at the close of my observa tions. They will be discussed in the present and two following chapters in a general manner. Facts observed both with man and the lower animals will here bemadeuseof;butthelatterfactsarepreferable, aslesslikelytodeceive us.

In the fourth and fifth chapters, I will describe the special expressions of some of the loweranimals; andinthesucceedingchaptersthoseofman. Ev eryone will thus be able to judge for himself, how far my three principles throw light on the theory of the subject. It appears to me that so many ex pressions are thus explained in a fairly satisfactory manner, that probably all will hereafter be found to come under the sameor closely analogousheads. I needhardlypremisethatmovementsorchangesinanypartofthebody, -as the wagging of a dog's tail, the drawing back of a horse's ears, the shrugging of a man's shoulders, or the dilatation of the capillary vessels of the skin, - may all equally well serve for expression.