Robert West has taken on a big task. Initially, he intended this book to be a compendium of theories of addiction, and it is that. However, unfulfilled by this task, he created a new theory derived from elements of other theories, drawing on the insights provided. The book weaves these two strands together, and I believe that both elements will be useful for many readers, though I think the book will be remembered most for the new theory.

The new theory is in fact a theory of motivation and the way that elements of the motivation system combine together to affect behavior. There is nothing inherent in the theory that applies to addiction, but the implications for the study of other kinds of behavior are not described in the book. The theory is known as PRIME theory: plans, responses, impulses/inhibitory forces, motives, and evaluations (www.primetheory.com). PRIME theory proposes that impulses and inhibitory forces influence behavior directly, and that higher elements influence each other. Thus plans influence evaluations, which in turn influence motives (or desires) and these act through the impulses or inhibitory forces. This calls attention to the second theme of PRIME theory, which is that behavior is under moment-to-moment control of impulses and inhibitory forces. Higher elements, such as plans and evaluations are generated fleetingly in each moment; West argues that many other theories have objectified and given a kind of internal permanence to concepts such as attitudes and self-efficacy. In West's theory, what gives the motivational system some stability is identity. The labels we give ourselves and the image we have of ourselves — such as that of being an ex-smoker — is what bolsters our motivation system against the temptation to smoke when we are giving up addictive behaviors. The theory calls attention to the plasticity of the motivational system and that all levels of the system are sensitive to learning and influence through habituation or sensitization, associative learning (such as classical or operant conditioning), and explicit memories. Thus, the motivational system behaves like a fly-by-wire aeroplane. The motivational system is exquisitely sensitive to inputs (and this is part of what leads humans to be so adaptable and has led to evolutionary advantage). However, this sensitivity needs constant balancing input as does the fly-by-wire aeroplane to keep it from spiraling out of control; addiction is explained by a lack of balancing input. It may arise because drug use changes elements of the motivational system (for example the way nicotine sets up classically conditioned responses with smoking cigarettes), or perhaps because individuals possess attributes such as depression that mean that the rewards of consuming the addictive substance are relatively greater, or that social environments place people at greater risk, by for example, normalizing smoking.

Chapter 2 defines addiction and sets up what West terms big observations about addiction — the big observations or questions that any complete theory of addiction should answer. For example, why are some substances more addictive than others? Why can most addicts stop, but few maintain abstinence? Why do addicts feel compelled to restart using a substance that they have vowed and seemingly want to live without? These observations, West argues, should be the primary test of any theory of addiction, and if a theory cannot answer these questions, then it should be abandoned. Chapters 3 through 6 consider existing theories of addiction, giving a description of each theory typically in 2-3 pages. It is then followed by a critique, where each theory is tested against the big observations on addiction. As someone who has not read widely about theories of addiction, I found these chapters gave me a really useful `crammer's guide' to many ideas that I was partly aware of but not fully conversant. Each of these chapters ends by drawing out the main themes that will be later incorporated into the synthetic theory of addiction. These chapters are helpful because the explanations are given in easy to understand language and clearly explained, often by reference to examples and by reference to the literature. There is a strong thread of common sense running through these chapters.

The final chapters set out the elements of PRIME theory in more detail. In the final chapter, the new theory is put through the same tests as applied to the other theory. Addiction is defined as a defect in the motivational system arising from one or more of the levels in PRIME theory. The theory is tested against the big observations about addiction. Finally, based on PRIME theory, West sets out some predictions that stem from the new theory. I hesitate to give an overall view of the theory, mainly because it is so different to any ideas I have had about the subject, and I think it needs time to sink in. However, I found that it gave useful insights into parenting my six year old that made sense of his behavior, which is some testament I think, and this new theory of motivation also fits well with my observations of smokers. I imagine this book will be widely read, and I strongly recommend that you do so.

About the Author: Paul Aveyard , M.D., Ph.D., is a senior lecturer with the University of Birmingham, UK. His research interests include pharmacological and behavioral trials for smoking cessation as well interventions in tobacco prevention.