Past studies have shown that people who self-identify as politically conservative are more likely to experience involuntary physiological responses to disgusting images. Now, researchers have taken things a step further by using brain scans to predict test subjects' political leanings with freakishly high accuracy.

Above: An example of a "disgusting image" shown to test subjects. This particular photograph is from a 2011 study that demonstrates "individuals with marked involuntary physiological responses to disgusting images, such as of a man eating a large mouthful of writhing worms, are more likely to self-identify as conservative and, especially, to oppose gay marriage than are individuals with more muted physiological responses to the same images."

The last decade or so has seen a number of studies published that point to a decipherable link between biology and political ideology, though the strength and directionality of that link โ€“ i.e., to what extent each affects the other โ€“ remains less than clear. Recently, researchers led by Virginia Tech professor Read Montague set out to assess "the provocative claim that neural responses to nonpolitical stimuli (like contaminated food or physical threats) should be highly predictive of abstract political opinions (like attitudes toward gun control and abortion)." Their findings, which appear (free of charge!) in the latest issue of Current Biology, suggest our brain activity is not only predictive of our political leanings, but stunningly so.

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WaPo's Rachel Feltman provides a compendious summary of the team's work and findings:

The researchers... report that images showing dirty toilets and mutilated carcasses could be used to predict political ideology with up to 98 percent accuracy.

In the experiment, subjects sat in a brain scanner while being shown a mix of images. Some of them were downright nasty, showing filth, rot, and decay. Others were neutral or pleasant โ€” like landscape shots, or pictures of babies. The researchers noted the neural response to each. Afterward, the study subjects took a political survey that asked them about their thoughts on issues, such as having prayer in public schools and same-sex marriage legalization.

The researchers... found that patterns of brain activity after viewing the gross images could be grouped together based on political leanings. In other words, conservatives reacted one way to the images (at least on a neurological level) and liberals reacted another way.

When asked to rate the disgusting pictures, one group wasn't more grossed out than the other. But the subconscious reactions varied enough for the researchers to tell conservatives and liberals apart.

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To the best of the researchers' knowledge, the findings are unprecedented. "This is the first fMRI study revealing multivariate patterns of brain activity that differ between liberals and conservatives during emotional processing of sensory stimuli," they write. "A single disgusting image was sufficient to predict each subject's political orientation" with 94% accuracy, Montague told Cell Press." I haven't seen such clean predictive results in any other functional imaging experiments in our lab or others."

It's an unsettling notion โ€“ that our beliefs could be, to borrow an exhausted and insufficient analogy, "hard-wired" into our neurophysiology. A belief system rooted in a quantifiable, biological substrate, after all, is presumably not only decipherable but malleable in ways that would make a political strategist salivate.

Lest we veer too far into tin-foil hat territory: We are obviously a very long ways away from any reality in which our belief systems are so precisely tinkered with. I mean, a 2012 study out of Cornell found the mere mention of hand sanitizer could temporarily render student test subjects more politically conservative โ€“ but we still don't understand why.

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[Current Biology via WaPo]