The Expression of the Emotions in Man and Animals in the field of comparative psychology and his impact on academic psychology was muted, partly because of the widespread influence of the behaviourist school during the twentieth century. The lavish style of biological illustration was followed in work on animal locomotion by photographer Eadweard Muybridge (1830–1904)(leading to cinematography), and by the Scottish naturalist James Bell Pettigrew (1832–1908); in the extensively (and controversially) illustrated works of the evolutionary biologist Ernst Haeckel; and – to a lesser extent – in D'Arcy Thompson's "On Growth and Form" (1917). Darwin's ideas were followed up in William James' "What Is An Emotion ?" (1884); and,
Body language postural expressions of emotions such as anger/aggression, happiness, and fear. These similarities support the evolution argument that social animals (including humans) have a natural ability to relay emotional signals with one another, a notion shared by several academics (Chevalier-Skolnikoff, 1974; Linnankoski, Laakso, Aulanko, & Leinonen, 1994). Where Darwin notes similarity in expression among animals and humans, the Cultural Equivalence Model notes similarity in expression across cultures in humans, even though they may be completely different. One of the strongest pieces of evidence that supports this model was a study conducted by Ekman and Friesen (1971), where members of a preliterate