Disputing Darwin: On Piloerection and Mental Illness

abstract: Most of Charles Darwin's ideas have withstood the test of time, but some of them turned out to be dead ends. This article focuses on one such dead end: Darwin's ideas about the connection between piloerection and mental illness. Piloerection is a medical umbrella term to refer to a number of phenomena in which our hair tends to stand on end. Darwin was one of the first scientists to study it systematically. In The Expression of the Emotions in Man and Animals (1872), he discusses piloerection in the context of his analysis of the expressions involved in fear and anger, relying heavily on the evidence provided by one of his correspondents, the British psychiatrist James Crichton Browne. This essay reveals how Darwin's initial doubts about the similarity between piloerection in animals and psychiatric patients were eased when studying photographic portraits of female psychiatric patients sent to him by Crichton Browne. It considers arguments against Darwin's reading of these portraits and the apparent contrast between this reading and his own skepticism, in later years, about the value of documentary photography. The article concludes with some notes regarding the reception of Darwin's ideas about psychopathology.