What was the title of Darwin's 1872 book on emotional expression?

Darwin’s 1872 book on emotional expression was The Expression of the Emotions in Man and Animals. It examined how humans and other animals communicate feelings through facial movements, gestures, posture, and bodily changes.

Darwin argued that many expressions are inherited rather than learned from scratch. He compared people from different cultures with infants, blind people, and animals to explore whether reactions such as smiling, fear, anger, grief, and surprise had common biological roots. The book extended evolutionary thinking into psychology and behavior.

The work was illustrated with photographs and drawings, making it an early landmark in the scientific study of facial expression. Darwin suggested that some expressions began as useful actions but later persisted as recognizable signals, while others could arise from nervous-system responses or opposing habits.

The title is sometimes shortened informally to The Expression of the Emotions, but the full canonical title includes “in Man and Animals.” It was published after On the Origin of Species and The Descent of Man, and it helped establish comparative research on animal behavior and human emotion.