There have been three major stages in the science of animal behaviour or ethology, and these have had a great impact on attitudes to domestic animals and to the welfare of farm and laboratory animals. Ethology can be said to have begun with the naturalists Lorenz, Tinbergen, Thorpe and others who wrote directly about their observations on animal behaviour. Then from the mid-1950s came behaviourism. The theory of behaviourism postulated, in its most extreme form, that animal and human behaviour may be explained purely in terms of muscular and physiological or hormonal reactions to external and internal stimuli. Behaviourism started with human psychology but spread to ethology from the influence of B. F. Skinner (1904-90) who, in the 1940s, developed the Skinner box for experiments to condition rats, whereby they pressed a lever to gain a reward or avoid punishment. The greatest sin that a behaviourist could commit was to be anthropomorphic.

animals have consciousness and indeed whether they should have rights, in the same way that since the abolition of legal slavery all human beings have rights, had been argued for hundreds of years. The discussions, which had been mostly between philosophers, remained mainly of academic interest until the mid-twentieth century. However, since the 1970s, with the demise of the behaviourist school of research in animal behaviour and the impact of the animal liberation and welfare movements, the study of animal consciousness has achieved the status of a scientific discipline, often called cognitive ethology.