Just in time for the annual Thanksgiving turkey overdose, MIT Technology Review has run Tryptophan, Turkey, and Trust by Emily Singer. Tryptophan is the enzyme abundant in turkey that has been shown to cause drowsiness. Many credit tryptophan for the postprandial coma holiday diners often: fall into. It is also a precursor to seratonin, an important brain signaling molecule. Long known for its role in depression, seratonin is now being studied by neuroeconomics researchers interested in its role in normal behavior. Robert Rogers of Oxford University finds that seratonin seems to have a role in social interactions and trust levels between individuals.

In the new study, presented earlier this month at the Society for Neurosciences meeting in San Diego, half of the volunteers were given a drink that depleted their tryptophan levels prior to the start of the game, thereby decreasing serotonin levels in their brain. Rogers and his team found that dampening serotonin activity significantly decreased the level of cooperation among the players, and that this group also rated fellow players as less trustworthy. “The findings suggest that a serotonin deficit might impair sustained cooperation,” says Rogers.

While it’s not clear why serotonin has this effect, previous research has shown that mutual cooperation might be rewarding in its own right: it enhances activity in the brain circuits that play a role in positive reinforcement. Rogers hypothesizes that reducing the chemical also reduces the reward value of cooperating.

Should neuromarketing-oriented advertisers redouble their efforts on Thanksgiving afternoon and evening in the hope that customers might be more trusting and receptive? Probably not. Although the levels of tryptophan needed to boost trust haven’t been determined, the drumstick you consumed probably won’t have much of an effect. This research may, however, explain why millions of turkeys end up on holiday tables without struggle or complaint: they are simply too trusting! :)

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