Going beyond ethics, scientists have found that physical experiences influence other aspects of cognition, too. In 2014, researchers in Germany had people read an ambiguous conversation while touching either a rough or smooth surface. When they touched the rough surface, participants were more likely to think the conversation was adversarial and harsh. And a 2010 Science study found that people tended to rate a job candidate more highly if the candidate’s résumé was attached to a heavy, rather than a light, clipboard.
So my urgent need to brush my teeth as I steered my boyfriend away from discovering his gift may not have been a tool to mask my untruths. Instead, it might’ve been a personal need to absolve myself of guilt as I cleaned my lying mouth. As Schaefer tells me, “The Macbeth effect is very interesting because it describes a link between physical cleaning and moral purity. When you’ve done something bad to a person, like lie, you have the need to clean your body, and if you get to, you feel better.”
This intrigued me, not only as a guilty, serial gift-liar, but also as a neuroscientist. And it has intrigued other neuroscientists and psychologists, too, such as Schaefer.
Surprisingly, that activity was much stronger after writing a lie than writing the truth
In a study published last December, he and his team asked 35 participants to read various scenarios and then speak or write a prepared response that was either truthful or a lie. In one scenario, the volunteers found an important document that could hurt a colleague if they didn’t return it. Then the subjects told the colleague they did find it (the truth) or didn’t (a lie). Afterward, researchers showed the participants two products: a hand soap and a toothpaste or mouthwash. Then they asked them to rank each product’s desirability on a 4-point scale.
Like previous studies, this one found that if participants lied, whether verbally or in a written note, they gave the hygiene products better scores than after telling the truth. If they spoke the lie instead of writing it, they rated toothpaste and mouthwash higher than hand soap (and vice versa.) So it seems people find cleaning the “dirty” part of their body — the part that commits the lie — more desirable than cleaning the “honest” parts.
But connections between cleanliness and morality have been made before; Schaefer wanted to know what was happening in the brain. “The interesting thing is we have a map in our brain of our body,” he says. “So, everything on our body surface is represented in that map.” It’s called the somatosensory cortex, and it’s organized by body part. A touch on the foot would register in a certain part of the cortex, and a touch on the nose, another.
Using fMRI, Schaefer and his team saw that when the study participants were rating hand-washing products, the part of their brains’ somatosensory cortex linked to the hand showed a flurry of activity. Surprisingly, that activity was much stronger after writing a lie than writing the truth. The same thing happened when they rated mouth-related products. After speaking a lie, the cortical area dedicated to their mouth was much more active while people scored toothpaste and mouthwash products than it was after they told the truth.
Now I’m faced with a problem. If my boyfriend reads this, he might wise up to my own Macbeth effect, giving me away during future Christmas discussions. Maybe there’s some other Shakespearean-inspired psychological phenomenon to help me deal with my lies? Or maybe I’ll exploit the findings of another study.
“The interesting thing is we have a map in our brain of our body,” he says. “So, everything on our body surface is represented in that map.”
In a paper published in Social Cognitive and Affective Neuroscience in 2011, researchers at Yale described their discovery that people who touched a warm object were more likely to invest money with a stranger than people who touched something cold. And, like Schaefer’s study, the team observed the temperature-influenced trust effect in the brain, in an area known as the insula. Along with regulating other functions, the insula becomes more active when someone faces risk.
When a participant held something cold before deciding whether to trust a stranger, the activity in the insula intensified. But when the participant held something warm, the insula remained in a calmer state. And a more relaxed insula is a more trusting insula.
Turns out this warmth angle may actually be doubly useful for me. In a 2008 Science study, marketing professor Lawrence Williams and social psychologist John Bargh found that people were more likely to pick out a treat for themselves if they had recently held something cold. Yet when they’d held something hot, they were more apt to choose a gift for a friend.
So maybe this December I’ll just manipulate my boyfriend’s insula and generosity with a warm cup of tea. What could go wrong?