The Bad Taste of Moral Turpitude

A new study reveals the oral origins of moral disgust

Protester in Iceland shows her disgust after US toxic assets infect global markets.
Image: Der Spiegel
The greed and avarice responsible for the current economic meltdown has resulted in a growing distaste for business as usual. As it turns out, evolution may explain just why this is. Speaking about his reaction to the economic crisis, Jeremy Warner, writing in the British newspaper The Independent, states that:

The spectacle of secretive deal-making on luxury yachts and at five-star hotels amid the Mediterranean playgrounds of the world's super rich leaves a bad taste in the mouth and is plainly offensive to the thousands of ordinary lives likely to be affected by it.

This kind of physical expression of distaste for immoral behavior is commonplace in our language. A used car salesman’s offer seems “fishy” or the crimes of a corporate banker are condemned as “wretched” behavior. Even the word "turpitude" is based on the latin root turpis for something foul. But why would something as abstract as morality be associated with these physical expressions of digust?

Now, a study by psychologist Hanah Chapman and colleagues in the latest edition of the journal Science (subscription required), has sought to understand this connection and its evolutionary implications. In a series of careful trials, carried out at the University of Toronto, Chapman recorded facial data while participants were engaged in three separate experimental conditions to simulate different forms of disgust: oral, visual and moral.

In the first set of experiments, the researchers focused on the levator labii muscle region of the face, the muscle group responsible for raising the upper lip and wrinkling the nose. These facial muscles were thought to be the most important group for the expression of disgust. By using a technique known as electromyography (EMG), the activation of the muscle cells in this region could be precisely recorded. EMG data were then recorded from participants while they drank small samples of unpleasant-tasting bitter, salty and sour liquids. Then, by comparing the muscle response of participants while drinking the foul liquids to that of something sweet or neutral (such as water), the researchers hoped to demonstrate the levator labii region as the muscles responsible for the expression of oral disgust.

Confirming their predictions, the unpleasant drinks caused significantly more activity from the levator labii than either the sweet drink or the water produced. With their baseline measurements established, Chapman and her team could then move on to determine if more abstract feelings of disgust tapped into the same brain network as the disgusting tastes did.


Foul tasting liquids cause levator labii muscles to evoke expression of disgust.
Image: Chapman et al.

The researchers then recorded EMG facial data while showing a series of disgusting photographs such as feces, serious injuries or crawling insects to elicit an expression of visual disgust in the participants. They also showed sad and neutral photographs to act as controls in the same way that the sweet liquid and drinking water did in the previous test. Once again, only the disgusting photographs resulted in a significant activation of the levator labii muscles and the characteristic appearance of disgust in the participant. Now that the same group of muscles were shown to be activated in two separate forms of disgust, the researchers moved on to their final goal: moral disgust.

Having determined that both the primitive distaste response and more complex forms of disgust evoke levator labii region activity that is proportional to the degree of disgust or distaste experienced, we next examined whether the same pattern of results would hold for moral transgressions. Given that fairness is a cornerstone of human morality and sociality, we examined the facial motor activity associated with violations of the norm of fairness.

The researchers used a simulation known as the Ultimatum Game to model unfairness in social interactions. In this game, two players split $10: The first player, the proposer, makes an offer suggesting how the money should be split, which the second player, the responder, can accept or reject. If the responder accepts the offer, the money is split as proposed, but if they reject the offer then neither player receives anything. Each participant played 20 rounds of the Ultimatum Game in the role of responder while EMG data recorded their facial movements. The offers ranged from “fair” (an even $5:$5 split) to very “unfair” (proposing a $9:$1 split). The EMG data was then used to interpret the varying levels of unfairness that participants experienced as part of the game.

What the researchers concluded was that, when offers reached very unfair levels (such as an $8:$2 or $9:$1 split) the levator labii muscles activated revealing the players feeling of disgust at being cheated. Fair offers or offers that were in the players favor did not evoke this response. These EMG responses fit with the self-report that participants felt about the level of unfairness. During times where they felt cheated, they were disgusted by the other player’s behavior and their face responded accordingly. As the authors summarized their findings:

When participants received unfair offers, they judged their experience as most similar to tasting or smelling something bad. . . even though the “bad taste” left by immorality is abstract rather than literal.

French poster condemning the economic crimes of the rich. No translation necessary.
Image: Snup Paris.com

What these findings suggest is that reactions based on moral disgust influence decision-making in the same way that oral disgust would keep you from eating something noxious. This was certainly the case in the Ultimatum Game as the more disgusted the responder was by an unfair offer the less likely they were to accept it. It would seem that our economic decisions are not based purely on logic, but also on a physiological response based on our innate reaction to immoral behavior. As principal investigator Adam Anderson told United Press International:

These results shed new light on the origins of morality, suggesting that not only do complex thoughts guide our moral compass, but also more primitive instincts related to avoiding potential toxins. . . Surprisingly, our sophisticated moral sense of what is right and wrong may develop from a newborn's innate preference for what tastes good and bad, what is potentially nutritious versus poisonous.

Perhaps what’s most intriguing about this study is the implication that moral disgust “hitched a ride” on the more primitive reaction to poisonous or spoiled food. This process, known as exaptation, is where a trait or behavior that was adapted for one function is later co-opted and used for something entirely different (such as bird feathers adapted for use in thermoregulation and only later being useful for flight). In this case it would seem that our evolved neurological template for moral behavior tapped into the previously existing neural pathway for oral disgust. In this way, a physical aversion to immorality could have served as a check upon anti-social behavior in our ancestors and helped to reduce its prevalence in the social group.

Morality has long been thought to be a learned behavior and that if evolution were true it would mean that we are condemned to live in an immoral universe. The current economic crisis would seem to suggest that humans are indeed rotten to the core and in need of moral salvation. However, what this study demonstrates is that our intuitive sense of moral crimes are the direct result of our evolutionary history. As we continue to rinse our mouths of the policies that led to our current crisis we should keep in mind that, while trickery and deceit are a permanent part of our character, evolution has provided us with the very skills we need to create the kind of society that doesn't leave us reeling with a bitter aftertaste.

Reference:

H. A. Chapman, D. A. Kim, J. M. Susskind, A. K. Anderson (2009). In Bad Taste: Evidence for the Oral Origins of Moral Disgust Science, 323 (5918), 1222-1226 DOI: 10.1126/science.1165565