EXPERIMENTAL ASSESSMENTS AND CLINICAL APPLICATIONS OF CONDITIONED FOOD AVERSIONS.

The history of conditioned food aversions is a bit like the history of imprinting. When Lorenz rediscovered imprinting he used it as a stick with which to beat the behaviourists, claiming that imprinting was a unique form of learning inexplicable in terms of classical or instrumental conditioning. In subsequent, more detailed research, many of the supposedly unique properties of imprinting more or less evaporated, so that, from the point of view of learning theory, imprinting ceased to be an ‘enfant terrible’. On the other hand, interest in imprinting has by no means diminished over the years because, while imprinting is no longer seen as an especially interesting form of learning, it is seen as an especially interesting phenomenon for a variety of other reasons. Something similar has happened with conditioned food aversions. Poison-avoidance learning in rats was initially seen as a direct and extremely serious challenge to established theories of conditioning: it presaged a veritable revolution in the minds of learning theorists. Subsequently, however, conditioned food aversion has been found to have many of the properties of ‘normal’ classical conditioning and so, like imprinting, it has gradually been robbed of much of its uniqueness as a form of learning. It now appears in textbooks on learning alongside Pavlov’s dogs, eyelid conditioning and the galvanic skin response as one of the established procedures for demonstrating classical conditioning. This does not, however, mean that interest in conditioned food aversions has diminished. Food-aversion learning, as this book amply demonstrates, has become a fast-rolling research bandwagon in its own right, and for a variety of reasons. The speed of the bandwagon can be judged from the fact that the book contains 28 tightly-packed chapters plus a bibliography of conditioned food aversions listing about 1400 references. Even more impressive than this, however, is the diversity of the book’s contents. Very few of the chapters consider food aversions specifically from the point of view of learning theory, that is, from the point of view of hypothetical associative processes underlying the learned aversion. Rather, they deal with topics such as the function of food-aversion learning as a biological protection mechanism; aversion learning within the general con.text of how animals learn about new foods; sensitive periods for the formation of learned aversions; conditioned aversions as a means of treating drug addictions, or as a way of assaying the toxicity of new drugs; the pharmacological and psychological effects of different toxins; and conditioned food aversion as a means of pest control. In addition, a couple of chapters step more or less completely outside the realm of classically conditioned aversions in individual animals. Instead, they consider whether or not aversions can be socially transmitted, and how research on learned food aversions has focused attention on other ‘natural’ learning situations. The chapters are divided into five separate sections, each of which is prefaced by a useful introduction to, and summary of, what is coming. Essentially, however, the book consists of a collection of independent research reports. It describes the state of the art, rather then reviewing developments since 1966, the date of Garcia’s classic paper. Like any bandwagon, food-aversion learning has attracted mediocre as well as worthwhile participation. It is not surprising, therefore, that the component chapters of this book are variable in quality. Some are both new and enlightening; some are old-hat; a few are thrown together in a lackadaisical manner with no concern for either content or form. Few ethologists would want to read the entire book, but anyone interested in learning or in feeding behaviour is likely to find stimulating ideas and nuggets of information amongst the contents. In addition, the book as a whole is instructive in that it conveys a strong overall impression that psychologists are becoming increasingly drawn towards a functional (that is, biological) approach to learning. And finally, the contents would constitute invaluable source material for an historian or philosopher of science interested in bandwagonology, or for a linguist specializing in the exponential growth of scientific jargon. T. J. ROPER School of Biology, University of Sussex, Brighton, BN1 9QG, U.K.