I found this article in the New York Times fascinating, particularly the information about how the brain confuses the literal and figurative.
Consider an animal (including a human) that has started eating some rotten, fetid, disgusting food. As a result, neurons in an area of the brain called the insula will activate. Gustatory disgust. Smell the same awful food, and the insula activates as well. Think about what might count as a disgusting food (say, taking a bite out of a struggling cockroach). Same thing.
Now read in the newspaper about a saintly old widow who had her home foreclosed by a sleazy mortgage company, her medical insurance canceled on flimsy grounds, and got a lousy, exploitative offer at the pawn shop where she tried to hock her kidney dialysis machine. You sit there thinking, those bastards, those people are scum, they’re worse than maggots, they make me want to puke … and your insula activates. Think about something shameful and rotten that you once did … same thing. Not only does the insula “do” sensory disgust; it does moral disgust as well. Because the two are so viscerally similar. When we evolved the capacity to be disgusted by moral failures, we didn’t evolve a new brain region to handle it. Instead, the insula expanded its portfolio.
Not only does the brain fail to distinguish rotten food from rotten behavior, it also fails to distinguish between being in need of a bath and dirty doings:
Another truly interesting domain in which the brain confuses the literal and metaphorical is cleanliness. In a remarkable study, Chen-Bo Zhong of the University of Toronto and Katie Liljenquist of Northwestern University demonstrated how the brain has trouble distinguishing between being a dirty scoundrel and being in need of a bath. Volunteers were asked to recall either a moral or immoral act in their past. Afterward, as a token of appreciation, Zhong and Liljenquist offered the volunteers a choice between the gift of a pencil or of a package of antiseptic wipes. And the folks who had just wallowed in their ethical failures were more likely to go for the wipes. In the next study, volunteers were told to recall an immoral act of theirs. Afterward, subjects either did or did not have the opportunity to clean their hands. Those who were able to wash were less likely to respond to a request for help (that the experimenters had set up) that came shortly afterward. Apparently, Lady Macbeth and Pontius Pilate weren’t the only ones to metaphorically absolve their sins by washing their hands.
And — get this — holding a warm drink affects judging personalities as warmer!
Another example of how the brain links the literal and the metaphorical comes from a study by Lawrence Williams of the University of Colorado and John Bargh of Yale. Volunteers would meet one of the experimenters, believing that they would be starting the experiment shortly. In reality, the experiment began when the experimenter, seemingly struggling with an armful of folders, asks the volunteer to briefly hold their coffee. As the key experimental manipulation, the coffee was either hot or iced. Subjects then read a description of some individual, and those who had held the warmer cup tended to rate the individual as having a warmer personality, with no change in ratings of other attributes.
The author goes on to talk about what really ends bloodshed and creates peace. Highly recommended reading!