Abstract: This article explores the contribution of animal psychology to animal welfare. Since animal welfare includes subjective welfare, it is crucial to know the subjective world of animals. Analysis of the concept of anthropomorphism is particularly important because it is a basic idea of animal ethics. The history of animal psychology, focusing on anthropomorphism and behaviourism, is briefly described, and then measurement of the subjective experience of animals in two ways, namely animal cognition and pleasure or reinforcing effects, is reported. Finally, it is suggested that animal welfare is not a permanently fixed idea, but a socially constructed one that can be changed. To gain widespread agreement about a socially constructed idea, it is important to know in which circumstances ordinary people employ metaphorical extension to an understanding of animal behaviour. In other words, a survey of “folk animal psychology” is important in order to establish a consensus about animal welfare.