The question remains, why the hedonic ceiling that is achievable with drug use is so high? Whereas evolution has not dealt with the amounts of drugs consumed, neither could it have provisioned for the future use of morphine, heroine, vodka, cocaine or hashish to enable such a high amplitude (and thus a very wide range) of their brain effects. Why are there in place mechanisms that allow development of craving, be it drugs or food (positive and negative reinforcements are both involved)? The latter, as well as other mania-like cravings supported by respective hedonic states and unrelated to drugs (e.g., gambling and other high-risk activities, sexual, kleptomania), suggest the answer to these questions. These conditions are extreme variants of the behaviors that have evolved to support actions of direct importance to Darwinian fitness (reproduction, resource procurement), thus highly motivated and reinforced by pleasure. While high, this hedonic ceiling is within the norm of our species’ reaction to natural stimuli.
