Kids face up to disgust surprisingly late

BOSTON — Young children have a gift for doing things that adults find disgusting. But kids themselves take a surprisingly long time, until about age 5, to grasp the meaning of adults’ facial expressions of disgust, according to evidence presented May 28 at the Association for Psychological Science annual meeting.

This conclusion flies in the face of a popular idea that evolution has produced an innate facial expression for this emotion that even infants should comprehend, said Boston College psychologist James Russell. Theoretically, an ingrained recognition of adults’ disgusted expressions would keep youngsters from eating poisonous and potentially fatal items or putting them in their mouths.

“From that traditional view, it’s surprising that kids don’t understand facial expressions of disgust until age 5,” Russell says. “But we find that, until then, they see a ‘disgust’ face as being angry.”

Russell regards the new results as consistent with his controversial rejection of an influential theory that six emotions that are built in from birth — happiness, sadness, anger, fear, surprise and disgust — appear in distinctive facial expressions displayed by people everywhere. Instead, Russell proposes that two core feeling dimensions, high arousal to low arousal and positive reaction to negative reaction, provide the building blocks for emotions that get elaborated in each culture.

Russell’s team has previously found that a majority of children misidentify feelings expressed in adults’ facial expressions. Even at age 14, a substantial minority still errs on this task.

In two new experiments, Russell and his colleagues observed that youngsters often know the meanings of words for emotions before they comprehend the meanings of the facial expressions that go with them. The researchers studied nearly 600 children age 2 to 7. Children lived in middle- to upper-income families in the Boston area.

Kids viewed images on a computer screen of adults displaying the six basic emotional expressions. The kids’ task was to assign faces to boxes at the bottom of the screen that had been designated for specific emotions, such as an “angry” box. The boxes were tagged with written labels for older children; the researchers read the expression names to younger subjects.

At age 2, children’s accuracy was limited to putting happy faces in a “happy” box. Toddlers treated all negative emotional expressions as being angry.

Shortly after age 3, an appreciation of sad faces emerged. About a year later, kids could accurately identify angry faces and had generally stopped putting faces with other negative expressions into the angry box. Correct designations of other facial expressions soon followed, with comprehension of disgusted faces appearing last.

Kids displayed an understanding of each expression at slightly later ages when emotion boxes were labeled with facial images rather than with written labels.

Children may not figure out the meaning of facial expressions of disgust until age 5, but they use words synonymous with disgust, such as “gross” and “yucky,” much earlier, remarked Stanford University psychologist Lera Boroditsky.

The concept of disgust encompasses a variety of concerns, from being appalled at moral infractions to being nauseated by the sight of worms, Russell noted. So kids could learn to use “gross” and related words in certain situations years before they recognize facial expressions for disgust, he proposes.

Psychologist Debi Roberson of the University of Essex in England agrees. Each emotional expression consists of numerous signature muscle movements on the face that children gradually learn to see as a meaningful whole, she says.