Links between positive affect and cognition in humans for application to future animal welfare research

Abstract

Animal welfare has to do with affective states, but animals cannot verbally express how they feel, meaning that indicators of affect must be sought in the realms of (non-verbal) behaviour, cognition and physiology. We scoped the human literature to identify cognitive functions linked to positive affect, as inspiration for research into cognitive indicators of positive affect in animals. In humans, positive affect and approach motivation are closely linked but the intensity of approach motivation varies between positive states. ‘Low-approach’ positive affect (e.g. mirth or contentment), most commonly induced in the reviewed studies, appears to facilitate selective attention toward reward, improve creativity, broaden attentional scope, increase cognitive flexibility where tasks present unusual items, and enhance memory for peripheral details. High-approach positive affect (e.g. desire) has sometimes opposite effects, which may resemble those of negative affect, although far fewer reviewed studies induced this affect type. High-approach positive affect seems to narrow attentional breadth and lead to enhanced memory for central details. Both low- and high-approach positive affect appear to promote problem-solving. While most human studies seem to induce low-approach positive affect, it is likely that many animal studies induce high-approach positive affect by using motivators to perform cognitive tasks (e.g. presentation of food rewards, peers, offspring). Taking this into account, alongside arousal and motivation effects, adapting the cognitive tests used in humans to non-human animal species has the potential to enhance our pool of potential indicators of positive affect and our ability to assess positive affect in animals, following rigorous validation.