Her original hypothesis was that children with higher interparental conflict scores would be worse at reading happy, angry and neutral faces. What she found instead was that children in high-conflict households fared just as well as the other children in discerning happy and angry expressions.

“They just couldn’t identify neutral accurately,” she said.

The study has limitations: The children were reacting to posed photos of the same youthful white actors. In real life, of course, faces are moving — something that limits the applications of numerous studies in this area. The children also misread neutral as happy about as often as they misread it as angry, which is different from some other studies in this area. And it’s possible that they will grow out of the tendency as they age, she acknowledged.

Still, the findings support a point other researchers in this field sometimes make: Those most in need of a benign interaction often have the hardest time recognizing one.

A parallel phenomenon has been shown to sabotage people suffering from depression and anxiety.

“People with anxiety disorders are likely to see fear when it’s absent,” and to “misclassify neutral expressions as angry, fearful, or just generally negative,” said Dr. Marsh, the Georgetown professor, who recently published a book called “The Fear Factor: How One Emotion Connects Altruists, Psychopaths, and Everyone In-Between.”

Depression, similarly, has been found to function almost like distortion goggles, filtering out signs of joy and happiness while magnifying signs of sadness or anger.

The good news is that there is some evidence that people can learn to see ambiguity in a more positive light.

Melissa Brotman, a clinical neuroscientist at the National Institute of Mental Health who develops treatments to help chronically irritable children, has found that they have a tendency to “perceive neutral or ambiguous faces as more hostile and fear-producing than typically developing youth.” But after a week of training with a computerized feedback tool in a small early pilot study, not only did the children stop seeing so much hostility in ambiguous faces, but parents and clinicians also noticed that their moods improved considerably.