They studied 42 parents of children with autism, a complex developmental disability that affects an individual's ability to interact socially and communicate with others. Out of which 15 parents were classified as being socially aloof.
"This manifests as a tendency not to prefer interactions with others, not to enjoy 'small talk' for the sake of the social experience, and to have few close friendships involving sharing and mutual support.
"This characteristic is really a variation of the normal range of social behaviour and not associated with any functional impairment," said psychiatrist Joe Piven at the University of North Carolina at Chapel Hill and director of the Carolina Institute for Developmental Disabilities.
In the study, parents were shown images depicting facial expressions of emotion that were digitally filtered so that only certain regions of the face were discernible--the left eye, for example, or the mouth. The researchers measured how they make use of the face to judge emotions.
The subjects were then asked to decide as quickly as possible if the emotion depicted was "happy" or "fear." The part of the face shown, and the size of the revealed area, randomly varied from trial to trial.
The team found that "aloof" parents relied much more heavily on the mouth to recognize emotion than they did on the eyes, as compared to non-aloof parents and, to a greater extent, to a group of parents of children without autism.
"We found that some parents who have a child with autism process face information in a subtly, but clearly different way from other parents," said neuroscientist Ralph Adolphs of the California Institute of Technology
"This is evidence for the hypothesis that the parents with the autistic child have brains that function somewhat differently as well," he added.
However, it is been currently investigated through brain imaging studies. One area of interest is the amygdala, a region located on either side of the brain in the medial temporal lobe that is known to process information about facial emotions and may have abnormal volume in both autistic individuals and their nonautistic siblings.
The finding indicates that certain aspects of autism do run in families.
"Our data strongly suggest that genetic factors make a substantial contribution to autism, but that does not mean that the entire cause of autism is genetic," said Adolphs.
"Together with many other studies, our study argues that genetic factors play a very important role in autism, while leaving open a role for other, environmental factors.
"We hope that this research contributes toward a cure for autism, even if only indirectly," he added.