Charles Darwin evolution animals

| is famous for his prolific writing about biology. In addition to publishing his theory of evolution, Darwin wrote books about coral reefs, earthworms and carnivorous plants. But the eminent naturalist made important contributions to more than just the life sciences. It turns out Darwin was also an early experimental psychologist.

Darwin conducted one of the first studies on how people recognize emotion in faces, according to new archival research by Peter Snyder, a neuroscientist at Brown University. Snyder’s findings rely on biographical documents never before published; they now appear in the May issue of the Journal of the History of the Neurosciences.

While looking through Darwin’s letters at the University of Cambridge in England, Snyder noticed multiple references to a small experiment on emotion that Darwin had performed in his house. With the help of librarians, Snyder uncovered the relevant documents—research notes and tables filled with the illegible scrawl of Darwin’s elderly hands and the neater writing of his wife Emma. Although Darwin’s fascination with emotional expression is well documented, no one had pieced together the details of his home experiment. Now, a fuller narrative emerges.

"Darwin applied an experimental method that at the time was pretty rare in Victorian England, " Snyder said. "He pushed boundaries in all sorts of biological sciences, but what isn’t as well known are his contributions to psychology."

In 1872, Darwin published The Expression of the Emotions in Man and Animals, in which he argued that all humans, and even other animals, show emotion through remarkably similar behaviors. For Darwin, emotion had an evolutionary history that could be traced across cultures and species—an unpopular view at the time. Today, many psychologists agree that certain emotions are universal to all humans, regardless of culture: anger, fear, surprise, disgust, happiness and sadness.

In writing Expression, Darwin corresponded with numerous researchers, including French physician Guillaume-Benjamin-Amand Duchenne, who believed that human faces expressed at least 60 discrete emotions, each of which depended on its own dedicated group of facial muscles. In contrast, Darwin thought the facial muscles worked together to create a core set of just a few emotions.