Your Brain Decides Trust in Milliseconds

What makes a person trustworthy? They keep promises? Don’t gossip? Responsibility? Well, whatever you think, your brain has other ideas. As per usual.

A study published in the Journal of Neuroscience (.pdf alert) has found that your brain decides if someone’s face is trustworthy in milliseconds, and it doesn’t do so logically.

Researchers monitored the brains of thirty-seven volunteers while showing them pictures of 300 faces for thirty-three milliseconds each. Each face had been rated by a different set of ten subjects, who saw the faces for much longer and rated their trustworthiness.

So what makes a trustworthy face? Turns out, we have pretty uniform opinions. Faces with “higher inner eyebrows and pronounced cheekbones are trustworthy, and lower inner eyebrows and shallower cheekbones are untrustworthy.” Also worth mentioning: some other studies have suggested that we can detect trustworthiness by subtle things like the amount of white in one’s eyes.

Anyway, each subject saw a face for thirty-three milliseconds, after which the image was replaced by “a neutral face mask for 167 milliseconds that disrupted further visual processing of the target”. Basically, research subjects only got to look at the faces subliminally.

Different parts of the brain lit up when research subjects saw untrustworthy faces when compared to trustworthy ones, and they lit up more when a face in question was suspicious. According to researchers, “Faces that appear more untrustworthy and likely to inflict harm are spontaneously tracked by the amygdala, so the amygdala could then quickly alter other brain processes and coordinate fast, appropriate responses to people—approach or avoid.”

So, that sinking feeling you get when approached by the weird guy at work? Your brain’s made that decision long before you consciously did. And that weird guy might not even be that weird at all—that’s just your brain, being a dick for no reason.



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