Serotonin in the News

Posted in Behavior at 9:14 am by justakim

This serotonin story has been in the news last week.

Serotonin functions as a neurotransmitter associated with anger, aggression, mood, and appetite. In this study, the appetites of half the participants were modified to have lower levels of serotonin. Then both groups were presented offers in an ultimatum game. One person suggests how to split a sum of money and the other can either accept their share and end up with something, but less than the other person. Or they can refuse, so that neither party receives anything.

In Crockett’s study, detailed this week in Science, 20 participants were given a number of attempts at the game, with fair offers, defined as 45% of the stake, unfair offers, defined as 30% of the stake, and very unfair offers, defined as 20%. Participants were randomized to get the serotonin-lowering treatment or a placebo.

While placebo participants rejected about 65% of very unfair offers, those with low serotonin rejected more than 80%.

Researchers also measured the mood, fairness judgement and reward processing of participants. They found these to be unaffected by lower serotonin, clearly implicating the neurotransmitter in the more aggressive response to injustice.

Or in other words, from TierneyLab:

But in this experiment the players rejected that deal 80 percent of the time when their serotonin levels were low, and it wasn’t because they were cranky or depressed, the researchers report. They conclude that lower levels of serotonin “can selectively alter reactions to unfairness,” and note that in the experiment this condition “increased retaliation to perceived unfairness without affecting mood, fairness judgments, basic reward processing or response inhibition.”

Now… I don’t have access to the article itself, and I know that they say that they controlled for all of these factors, but only using only 20 participants seems weak to me. 10 people got the placebo. 10 people got the serotonin-reducing drink. I’m sure the difference is significant but the sample size is so small, I’m skeptical.

The other thing that I’m leery of is the whole slew of conclusions across the swath of stories reporting these results. They would have you believe that this is proof that low serotonin causes aggression, impulsivity, poor social decision-making, irrational behavior. Are these really the reasons for intolerance of unfairness?

I don’t have much tolerance for it myself. My integrity and pride has a certain value, and I would rather maintain a reputation of fairness than accept some spare change. Yes, I can be induced to accept an unfair deal, but it’d either entail a significant sum of money, or a benefit down the line. Perhaps I am aggressive. Perhaps I am angry. But I’m not cheap.

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