John Timmer reports on studies from the journal Science which suggest that ineurotransmitter levels influence perceived fairness:

Exploring the neurochemistry of fairness

First, consider the notion of innate fairness. People who participated in a experimental transaction called the Ultimatum Game (a simple 2-party example of game theory) tended to reject offers they perceive as ‘unfair’ even though doing so results in them receiving less. This reinforces a recurring theme in current economic theory that participants often act fundamentally irrationally (e.g. Dan Ariely’s Predictably Irrational and other efforts in behavioral economics). One hypothesis drawn from the Ultimatum Game is an underlying evolutionary selection of a shared ‘golden rule,’ given the comparative advantage of group cohesion this might reinforce.

Second, the implications of the neurochemistry itself are more sobering. Even basic negotiation is often based on latent manipulation through psychological leverage; more advanced techniques sometimes exploit physiological factors such as room temperature or sleep deprivation to affect pliability. The casino industry has invested heavily in psychological profiling both in developing comp systems and interior design to lower inhibitions and increase the desire to stay on the gaming floor (high ceilings, rounded walls, indirect lighting, running water)—some examples are given in a short featurette on the DVD for Ocean’s Thirteen. Pushed a little further, you can see some of the same techniques deployed in the fields of law enforcement and the military as interrogation aids, as well as within specialized training such as SERE. In each case, the environment and physical comfort of the targeted participant are manipulated to lower their resistance, gain their trust, or ultimately obtain some concession.

Moving from science to science fiction, you can find ready parallels to controlling serotonin and oxytocin with the Pax used to curb aggression on the Outer Rim planet Miranda in Joss Whedon’s Serenity; the drug Prozium in Equilibrium and Soma in Brave New World; and more obscurely, the hormones produced by alien Powers that activate the ‘god module’ (aka neurotheology) in humans from Walter Jon Williams’ Voice of the Whirlwind. In each, the population is effectively controlled through their own neurochemistry by instilling languor, reducing aggression, suppressing emotion, etc.