Partisanship goes beyond rational discourse. It becomes membership in a tribe. This tribalism goes beyond policy-making, it becomes a mark of identity where your group fights off the other group. This leads to prejudice, irrationality, and closed-mindedness. I think we’re all susceptible to this bias.

It turns out partisans are really are prejudiced and irrational.

So here we go with neuroscience again:

By scanning subjects’ brains while they were thinking about people either politically like or different from them, researchers have found that different areas of the brain are active in the two cases. The researchers said their findings offer insight into the neural machinery that gives rise to perceptions that other racial or ethnic groups are different from one’s own.

Here’s what they did. They picked Boston college students who were ardent “liberals” – those believers in free inquiry and tolerance, you know. They then measured them to see if they self-identified with a target person.

Specifically, one “target” person was described as having liberal views and taking part in activities typical of students at Northeast liberal arts colleges. The other person was described as a fundamentalist Christian with conservative political views and activities–unlike most of the students.

The researchers found that the ventral mPFC region was, indeed, more engaged when subjects considered the target person like them, and the dorsal mPFC region was more engaged while considering the target unlike them… The researchers found that the more similar the subjects considered themselves to either target, the greater the response in the ventral mPFC. Conversely, the more dissimilar they considered themselves from the target person, the greater the activity in the dorsal mPFC.

This is interesting.

This means that if you identify someone as a member of your political tribe, you approach them with positive emotions and engage the rational portion of your brain. Membership in the tribe grants you access to a person’s trust.

On the otherhand, if someone is a political “other” who has different politics from you, then your mind is flooded with negative, distrusting emotions and the rational part of your mind closes.

Basically, liberal Boston College students are racists. We all are.

This is perhaps an evolved trait. Hunter-gatherer tribes competed for resources in a difficult environment. Other tribes were rivals for survival. So how do you interact with the Other? You stab them with pointy-sticks, that’s how.

Here’s the full paper.
Judgments of Similar and Dissimilar Others

There are some other studies that show partisans interprete new information through emotion rather than reason. Partisans select information which reinforces their belief and makes them feel good while emotionally blocking off contradictions.

This shows the danger of identifying yourself as a member of a political tribe or identity group. Identity groups are social constructs that encourange irrationality and bias against rivals.

Wonderful. This is somewhat damaging to the ideas produced social science. The ignorant will continue to make up myths and fantasies regardless of any empirical evidence. In fact, I’m doing it right now, those damned people unenlightened hoi polloi.