The putative reward function of equine stereotypic behaviour

A review of physiology and behaviour–based studies on the function of stereotypic behaviour indicates contradiction and inconsistency within the literature. By considering appropriate neurochemical data alongside an existing model of motivation (Hughes and Duncan, 1988), a greater understanding of the function of stereotypy may be gained. The Hughes and Duncan model (1988), described stereotypies as highly motivated appetitive behaviours performed repeatedly in an environment where consummatory goals are denied. Moreover, appetitive behaviours activate reward circuitry such as the ventral tegmental area and nucleus accumbens and are thus considered to have a reward value associated with their performance (Carr, 2002; Jones et al., 1990). Stress induced sensitisation of reward circuitry may result in appetitive ‘stereotypies’ having increased reward value, perhaps becoming consummatory in their own right. In such a scenario, stereotypic behaviour could function as a coping tool, allowing the animal to counter the effects of an aversive environment.