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Readers of this Journal have, through the work of Jaak Panksepp (e.g., ), become accustomed to thinking about the ascending mesolimbic dopamine system. Panksepp refers to it as the “seeking” system (and Kent Berridge, in related work—e.g., Berridge & Robinson, 2003—refers to it as the “wanting” system, a term that purposely neglects the motor aspect of dopaminergic function to which “seeking” calls attention). The concept of seeking is crucial to a neuropsychoanalytic understanding of the human mind/brain, because of its correspondence to the Freudian concept of drive. Indeed, seeking has broad implications for human culture. Perhaps, some readers may feel, even Tennyson's Ulysses—the heroic everyman, whose mission was “to strive, to seek, to find, and not to yield”—can be understood at least in part as possessing a dopaminergic system that would not relent. Speculation aside, most readers are further accustomed to thinking about several key brain structures in the seeking system. First and foremost, these are the ventral tegmental area (VTA), in which dopamine is produced, and the nucleus accumbens (aka the ventral striatum), to which it is first exported. Beyond these, various limbic regions—most importantly the anterior cingulate cortex (ACC), amygdala, and orbitofrontal cortex—are end targets where the reward-encoding effects occur. Generally put, dopamine appears involved in encoding the salience—which can be thought of as the absolute value of the valence (e.g., good or bad, rewarding or punishing)—of environmental stimuli. For example, a hungry man could expect to experience increased dopaminergic firing on exposure to a slice of pizza, and decreased firing on biting into it and tasting something unpleasant. An apparently rival, but most likely complementary, hypothesis of dopamine is the “reward prediction error” model of . This complex-sounding concept refers to a rather simpler idea: that dopamine is used to measure the difference between expectations and