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The assessment and promotion of positive affective states as opposed to consideration of negative states alone has now become an accepted component of animal welfare thinking. However, methods for assessment of positive affective state are comparatively underdeveloped compared with their negative counterparts. Due to the current lack of established physiological methods for assessing positive effect in animals, behavioural measures are likely to be the closest proxies. In this paper, we broadly review spontaneous behavioural measures that have been utilized in mammals to determine positive affect. This includes luxury behaviours, facial expression, vocalizations and laterality. Play and anticipatory behaviours expressed in animals have received greatest research attention. However, these methods require care in interpretation due to the influence of age and other factors, such as social status on their …