The challenge for the CPDD is to derive, utilize, and defend scientific standards for defining abuse liability. The tautological argument that a definition of abuse must include marijuana use because marijuana use must be drug abuse is exactly the misuse of terminology both Cicero and Brady have complained about above. Nonetheless, the question of validity is always important in evaluating scientific reasoning.

"How can the self-administration model validated? First, . . .there must be concordance between animal and clinical results. In order to define the limitations of methodologies, more effort should be placed on determining the reasons for discordant results. Secondly, there also must be some sort of concordance between both the incidence and perniciousness of street abuse on one hand, and the results of both animal and clinical studies on the other. Because fads and trends play a major role in drug abuse patterns, a good concordance can be expected only for those drugs whose street abuse is well established."(25)

The validity of the conceptual model behind reliance on self-administration has been established by research on the biological actions of drugs of abuse. Brady discusses the synergy between biology and behavior in his acceptance of a lifetime achievement award from the CPDD in 1990.

"[L]aboratory procedures for the generation and maintenance of drug self-administration have become the hallmark of abuse liability assessment based upon the kind of functional models that have proven most useful and productive in the experimental analysis of behavior. The most important conceptual and methodological consequence of this interactive research has been the analysis of relationships between the biochemical/ pharmacological properties of drugs and their environmental/behavioral stimulus functions."(26)

"The explosive advances in new knowledge of neurotransmitter and receptor dynamics combined with the demonstrated specificity of action and good correspondence with drug discrimination generalization profiles now provide a more precise behavioral reflection of neurochemical mechanisms."(27)