Who Needs Emotions? The Brain Meets the Robot

organization of motivational–emotional systems 63
Figure 3.7. Crayfish prefer an environment associated with the psychostimulants
amphetamine or cocaine. A: Crayfish were infused with the
drugs and then placed in a striped visual environment; control infusions
were associated with a plain visual environment. On a test trial following
conditioning, no drug was given and the animals were allowed to swim
through the aquarium. B: Significantly more time was spent in the presence
of psychostimulant-paired contextual cues. * = significantly different with
respect to control; # = significant difference between amphetamine and
cocaine values. (From Panksepp & Huber, 2004, with permission.)
wondering about the ultimate or functional causations of behavior, or “why”
drug use and addiction have evolved as major human behaviors. Clearly,
chemical systems mediating emotions and adaptive survival behaviors did
not evolve so that humans could discover the benefits of pleasurable drug
states. The field of Darwinian medicine explores the mechanisms of natural
selection that lead to vulnerability to disease (including addiction), and here
some insights have been provided. Certain genotypes may have conferred