Figure 1.

Modes of emotion expression.

Emotions are expressed through several modalities summarised in this schematic. Across species (inner circle) organismal response to a relevant stimulus can evoke changes in locomotion, motor behaviour, facial expressions, vocalisations, cardiovascular, gut and endocrine reactions and arousal (outer circle). Emotions, together with their expressions, have been proposed to encompass different features (middle circle) which are explained in further detail in Box 1.