Surprise and disgust are each considered to be a primary emotion, accompanied by very distinct patterns of facial expression. Investigators who study facial expressions have pointed to some key indicators of surprise in adults’ and children’s faces: raised eyebrows, wide eyes and sometimes an open mouth. The ability to recognise expressions of surprise appears to develop gradually between early childhood and adulthood. Surprise has traditionally been seen as a neutral or possibly positive emotion. In contrast, disgust has long been recognised as a fundamental negative emotion. Perhaps because of the obvious difference in the length of adult and infant noses, the expression of disgust appears to be somewhat harder to identify in young infants. In evolutionary accounts of emotional development, the ability to recognise and react to other people’s expressions of disgust is thought to be critical for children’s avoidance of sources of contagion and contamination in the environment.