The Expression of the Emotions in Man and Animals allows cultural factors only an auxiliary role in the shaping of expression. This biological emphasis leads to an appreciation of the universal nature of expression, with its implication of a single origin for the entire human species; and Darwin points to the significance of emotional communication with children in their psychological development. Darwin 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 (probably inspired by his cousin, Francis Galton) in his preparatory
The Expression of the Emotions in Man and Animals shows how human emotions link mental states with bodily movement, and are genetically determined, deriving from purposeful animal actions. He comments on the implications of the book: a single origin for the entire human species, with universal human expressions; and he stresses the social value of expression, citing the emotional communication between mother and child. This was one of the first books to be illustrated with photographs – with seven heliotype plates – and the publisher John Murray warned that this "would poke a [terrible] hole in the profits". The published book assembled illustrations rather like a Victorian family album,