Assessment of positive welfare: a review.

As a complement to the concentration on negative states in welfare science, scientists are increasingly considering the desirability of measuring positive outcomes. Since evaluation of an animal's mental state is a critical goal for welfare assessment, considerations of both positive feelings (what an animal "likes") and resources that an animal is motivated to obtain (what an animal "wants") appear to be important. However, since animals may make choices that are not in their long-term interests, an assessment of positive feelings and resources should include an evaluation of any associated actual or potential harms, such as fear, distress, pain, injury and disease. A review of current evidence suggests that positive welfare can be best assessed by evaluation of resources (i.e. inputs) that are valued by an animal and by positive outcomes such as behavioural responses, influences on cognitive processes and physiological markers. Since negative welfare is often inversely correlated with positive welfare measures, current welfare policy will have been achieving some positive welfare outcomes, however the explicit inclusion of positive welfare outcomes in the framework allows for analyses that are both deeper and more in tune with commonsense, which can hopefully yield more objective policies.