Moral Disgust Linked to Primitive Emotion

A new study reveals insights into the ancient roots of our
modern-day sense of moral disgust.

Research from the University of Toronto suggests that our sense of right and
wrong appears to be directly linked to a primitive survival instinct that
caused our ancient ancestors to find foul-tasting, poisonous foods
disgusting.

The study appears in the Feb. 27 issue of the journal Science.

"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," principal
investigator Adam K. Anderson, PhD, says in a news release.

Morality and Disgust

Morality has been widely considered to be a somewhat recent phenomenon,
evolutionarily speaking, that is closely tied to our ability to reason.
Disgust, on the other hand, is considered an ancient and primitive emotion,
which helped to keep early humans from eating foods that would kill them.

Anderson, lead study author Hanah Chapman, and colleagues conducted a series
of experiments designed to determine if morality and disgust are more closely
related than experts have thought.

"We wanted to see if there was any truth to the expression, 'It left me
with a bad taste in my mouth,' when we talk about something that is morally
offensive," Chapman tells WebMD.

"Does that have anything to do with the feeling that you get when you
open up that take-out container that has been in the fridge too long or walk
into that subway bathroom that hasn't been cleaned in a long time?"

The researchers employed a technique known as electromyography to record
electrical activity that directs muscle movements.

They focused on one specific muscle, known as the levator labii, which is
involved in raising the upper lip and wrinkling the nose -- movements
characteristic of the facial expressions people make in response to
disgust.

'More Than a Metaphor'

In one experiment conducted to evoke the most basic, primordial form of
disgust, participants drank a bad-tasting bitter liquid. In another, they
looked at pictures of things generally recognized as disgusting, like dirty
toilets.

In the final test, which measured moral disgust, participants were treated
unfairly in a classic psychological experiment.

In all three situations, the participants showed activation of the levator
labii muscle, indicating that reactions to tasting something bad, looking at
something disgusting, and experiencing unfairness all involved similar
disgust.

"People think about morality as being this pinnacle of human evolution
and development," Chapman says. "But we showed that this very old and
primitive response is playing an important role, too."

Harvard researcher Joshua D. Greene, PhD, tells WebMD that the research is
consistent with studies he has done suggesting that emotion plays a key role in
moral judgment.

"The idea that the emotion that causes us to reject something poisonous
has been co-opted for use in social judgment is certainly intriguing," he
says. "This study does not prove this, but it is pretty strong evidence for
the idea that disgust in a moral context is more than just a metaphor."

By Salynn Boyles
Reviewed by Louise Chang
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