The Expression of the Emotions in Man and Animals

The Expression of the Emotions in Man and Animals is a work of observational natural history that asks how and why feelings show themselves in the body. Darwin sets aside physiognomy, the reading of fixed features, and concentrates on the movements, postures, and changes that accompany emotion as it is actually felt.

He opens by stating three chief principles. The first is that of serviceable associated habits: actions once useful under a given state of mind become habitual and are then performed whenever that state recurs, even when they serve no purpose. The second is the principle of antithesis: an opposite state of mind tends to produce directly opposite movements, even useless ones, simply because they contrast with the serviceable ones. The third is the direct action of the nervous system, by which strong excitement generates nerve-force that is discharged in expressive ways independent of habit or will.

To test whether particular movements truly express particular states of mind, Darwin draws on several kinds of evidence. He observes infants, who show emotion with great force and little disguise; the insane, who are subject to strong and unchecked passions; the works of painters and sculptors; and the expressions of common animals such as dogs, cats, and monkeys. Animal evidence is treated as especially trustworthy because it is less liable to deception.

Much of the book catalogues specific states: suffering and weeping, low spirits and grief, joy and tender feelings, reflection and ill-temper, hatred and anger, contempt and disgust, surprise and fear, and finally shame and blushing. Throughout, Darwin argues that the chief expressions are innate or instinctive rather than acquired by each individual, since they appear in the very young, in animals, and with striking uniformity among peoples who have had little contact with one another.

The concluding chapters draw the larger lesson. The community of expression between man and the lower animals, and the bristling of hair or baring of teeth that survive in us, are most intelligible if man descended from a common progenitor in a far more animal-like state. Darwin also notes that expression matters for life itself: it is the first means of communication between mother and infant, it can reveal thoughts more truly than words, and the free expression of an emotion tends to intensify it while restraint tends to soften it.