The paper ‘What neurobiology cannot tell us about addiction’ arose from a conference, the International Addiction Summit held in Melbourne, Australia, in July 2008. Participants at this summit were invited to be as provocative as they wished, in order to stimulate new ways of thinking about addictions. The four commentaries above suggest that the paper has been moderately successful in provoking. All four raise interesting and significant points, even if they disagree in part with the arguments put forward.
Iguchi & Evans  disagree with the contention that studies involving drug administration by the experimenter rather than self-administration are ‘flawed’, and cite the important information that can be obtained from comparisons of the effects of experimenter-administered versus self-administered drugs . I agree completely that such comparisons can provide important information about the neural mechanisms involved in addiction. My use of the term ‘flawed’ applied to studies which employ only experimenter administration of drugs, and regard it as a model of addiction. It is surely not a novel idea that addiction is a disorder of drug-taking as opposed to a disorder of drug action. Koob , cited by Iguchi & Evans, states clearly that ‘drug addiction can be defined by a compulsion to seek and take drug’.
Iguchi & Evans also argue that self-administration was not the only feature differentiating wounded American Civil War veterans who became addicted to opiates from hospital patients who do not become addicted despite receiving large doses of opiates administered by nurses or physicians. They point to post-traumatic stress, unemployment, mental illness, social disruption, genetic vulnerability and other factors that may have differentiated between the two groups. Such factors are also often present in non-addicted patients, but it is precisely because of the multiplicity of factors that modify the response to the same drug in different subjects that one must attempt an integrative approach, rather than examining only the interaction between the drug and specific components of the brain.
This is the main point of the paper, and to varying degrees all four commentaries appear to agree. Iguchi & Evans accept that reductionist approaches ‘are placed in more appropriate context within appropriate and integrated conceptual frames’. This is a much weaker acceptance of the need for integrative thinking than that set out in von Bertalanffy's general systems theory , which is based upon many observations that complex interactive systems function under different laws than do simple isolated processes.
The other three commentaries [6–8] agree more clearly with the need for an integrative approach to addiction research, and bring up important reasons for it. Carter & Hall  rightly stress the risk that social policies designed to prevent addiction by reducing the extent of hazardous drug use may be ignored if excessive emphasis is placed on a neurobiological search for a magic bullet. Potenza  underlines the reciprocal interactions between drug actions, environmental factors and decision-making processes, and describes a potential model for an integrative approach to the study of such interactions. He also points out the need for integrative thinking in the definitions of addiction in future editions of ICD and DSM.
In view of such compelling reasons, one must wonder why the reductionist approach is still so dominant in addiction research. Spanagel  provides one of the reasons: the sheer joy of working in such an exciting and rapidly productive area as contemporary neurobiology. However, another important reason is that granting bodies evidently prefer this approach; their possible reasons for such preference deserve study.