Balancing the animal affective scales - Can the methodology of human affect balance be translated to other sentient species?

Assessing the welfare of non-human sentient animals is a multifaceted scientific endeavour. A human psychology approach that holds promise for application to animals is affect balance, based on the idea that how one feels most of the time is determined by the balance between the separate dimensions of positive and negative affect. Affect balance has been shown to have profound relationships with mental and physical health and well-being in humans. The aim of this conceptual article is to evaluate whether the affect balance methodology might offer a useful integrative measure of the affective/hedonic component of animal welfare and to outline key considerations for its potential application. Due to the variation in human affect balance methods, any attempt to translate them to other species requires first extracting their main underlying principles. We extracted four underlying principles, the first three relating to estimating the frequencies of positive and negative affect over time, and the fourth relating to the integration of positive and negative affect into an affect balance score or category. We then discuss how the theory behind the affect balance methodology can be translated to other species, and the theoretical and practical considerations in the development and validation of potential assessment methods. Altogether, we think that this approach holds great potential for animal welfare science and we encourage empirical studies into this topic.