The Expression of the Emotions in Man and Animals is a book by Charles Darwin, published in 1872, concerning genetically determined aspects of behaviour. It was published thirteen years after On the Origin of Species and, alongside his 1871 book The Descent of Man (of which it was originally intended to form a part), it is Darwin's main consideration of human origins. In this book, Darwin seeks to trace the origins of such human characteristics as the pursing of the lips in moments of concentration and the mental confusion which typically accompanies blushing. Before Darwin, mental life had often been considered in terms of associationist psychology. Darwin's biological approach links mental states to the neurological organization of movement; and he sought out the opinions of some leading British psychiatrists, notably James Crichton-Browne, in the preparation of the book which forms his main contribution to psychology. Amongst the innovations with this book are Darwin's circulation of a questionnaire in his preparatory research; simple psychology experiments on emotional recognition with his friends and family; and (borrowing from Duchenne de Boulogne, a physician at the Salpêtrière) the use of photographs in his presentation of scientific information. The Expression of the Emotions is an important landmark in the history of book illustration.