Machiavelli advocated deceit. In The Prince, he wrote that “no enterprise is more likely to succeed than one concealed from the enemy until it is ripe for execution.” So it would be a problem for a would-be Machiavellian if there existed some method for identifying amoral backstabbers before they plunged the knife.
A new paper hints that there might be such a method. Researchers gave 43 salespeople the Mach-IV test, which is a commonly used exam to determine whether someone has Machiavellian tendencies. They then used a 3-D MRI machine to analyze the subjects’ brain structures. Researchers hypothesized that that there would be differences in volume in certain regions -- basal ganglia, prefrontal cortex, insula, and hippocampus -- between so-called high Machs and low Machs.
And that’s what they found. There were, they write, "[s]ignificant positive differences for high versus low Machiavellianism” in gray matter volume in those particular areas of the brain. They speculate that this is because of neuroplasticity, that is, the fact that the brain physically changes in response to environmental factors. Just as teaching people to juggle alters the structure of their brains, perhaps being deceitful bulks up one’s left prefrontal cortex, which is “used in planning to outsmart people and regulation of negative feelings.”
There are an abundance of caveats here. Because of the small sample size and the fact that only people from one profession were studied, the results may not apply to the rest of us humans. And it’s not as if they isolated a Machiavellian part of the brain; the left prefrontal cortex isn’t employed just for nefarious purposes.
Besides, the results don’t do you much good if you’re trying to figure out whether the guy two cubicles over is plotting against you. Bob is unlikely to provide you with MRI scans of his brain.
But maybe the answer is in his face. A 2009 paper tried to determine whether we know someone has Machiavellian tendencies just by looking at him. Researchers showed participants pictures of the faces of people who had taken the Mach-IV. Using functional magnetic resonance imaging, they found that participants’ amygdalas, which process emotion, were activated more when they viewed the faces of high Machs. They also lit up when they viewed people who scored high on psychopathy measures, though not on faces of people who scored high on narcissism (incidentally, psychopathy, Machiavellianism, and narcissism make up what psychologists ominously call “the dark triad”). From the paper:
This indicates facial geometry contains accurate and reliable signals that reflect an individual’s trustworthiness and the neurology associated with threat detection is sensitive to these features.
Again, there are reasons to be skeptical. I haven’t come across follow-ups to this study (let me know if I’ve missed them) and there are scientists who think this kind of light-it-up brain-scan research is hooey.
Both of these studies depend on the widely used Mach-IV measure, which asks participants to agree or disagree with 20 statements like “All in all, it is better to be humble and honest than to be important and dishonest” and “Most people who get ahead in the world lead clean, moral lives” and “The best way to handle people is to tell them what they want to hear.” You have to wonder whether a true high Mach would really answer those questions honestly.
(The first paper mentioned is titled “The Making of the Machiavellian Brain: A Structural MRI Analysis” was published in the Journal of Neuroscience, Psychology, and Economics. You can find the abstract here. The second paper, “Trustworthy? The Brain Knows: Implicit Neural Responses to Faces that Vary in Dark Triad Personality Characteristics and Trustworthiness” was published in the Journal of Social, Evolutionary, and Cultural Psychology. The full paper is here.)
