Fifty years ago, learning theory, whose principles were derived from experiments on conditioning in animals, was a central focus of much of experimental psychology. But the cognitive revolution that swept through human experimental psychology in the 1960s, especially when it was taken up by many animal psychologists themselves, seemed to consign traditional learning theory to the scrap heap. Liberation from the shackles of old-fashioned behaviourism, however, should not be bought at the price of dismissing associative learning theory. Suitably modi ed and extended, associative theory is capable of explaining much of the behavior of animals and of pointing precisely to the ways in which that behaviour is complex. And under some circumstances, at least, the behaviour of people mirrors that of other animals and is equally amenable to an associative analysis. preface to Munn' s Handbook of psychological research in the rat, commended the volume as essential reading for undergraduate and graduate students as well as professional psychologists [who] will nd in these pages a treatment of some of the most important aspects of general modern scienti c psychology (Carmichael, 1950).And anyone who has read Hull' s or Skinner's autobiographies (Hull, 1952; Skinner required three volumes for his : Skinner, 1976: Skinner, , 1979: Skinner, , 1983 will not be left long in doubt about the value they placed on their work.If this was hubris, divine retribution was swift and harsh. The decline of animal learning theory from its pinnacle of importance was rapid and, at one time, seemed complete. Two sets of statistics give some measure of the change. In 1946, the American Psychological Association published two main journals devoted to reports of empirical research in mainstream experimental psychology, Journal of Experimental Psychology and Journal of Comparative Psychology. In that year, just over 20% of the articles appearing in the former, and 50% of those appearing in the latter were reports of experimental studies of animal learning (narrowly de ned-excluding, for example, research on animal behaviour, ethology, or physiological psychology, which made up the other 50% of the Journal of Comparative Psychology). Thirty years later, in 1974, the last year in which the Journal of Experimental Psychology was published as a single journal, less than 5% of its articles were on animal learning, and the contents of Journal of Comparative and Physiological Psychology, which had long since replaced Journal of Comparative Psychology, were now largely (over 75% ) devoted to physiological rather than comparative psychology.More recently, Thomas and Blackman (1991) reported that between 1977 and 1989 there had been a decline of over 20% in the number of British psychology departments with an animal laboratory. They also reported that although there had been a signi cant increase in the overall number of research students in psychology over this 12-year period, the number undertaking research requiring a Home Of ce licence had halved.What is t...