Evolutionary tracking of general mechanisms of addiction liability inevitably reaches the level of basic engines of behavior, emotions. Emotions, reflecting perceived reward and punishment, incentives and deterrents, are also the “common fitness metric across different stimuli . . . along which everything, from apples to oranges to cocaine, can be compared” (Panksepp et al., 2002, p. 460). It is illustrative that the brain areas responsible for extinction of fear, one of the primary emotions, and addiction overlap (Peters et al., 2009). The downside of having evolved such common fitness scale is that the brain has also become prone to evaluating cocaine to be as good or, indeed, much better than “apples and oranges”. Whereas the mechanisms underlying the CLA are grounded in this ancient and highly conserved system, which determines incentive motivation and reward-pursuing behavior, drugs produce a false signal of fitness benefit that is very potent (Nesse and Berridge, 1997). Drugs circumvent the complex modulators determining input into the system that assigns a fitness value to an action or experience, by acting upon the system itself. The input provided
