BRISTOL, England -- Autistic children have an impaired ability to place unfamiliar faces in memory, possibly explaining some of the social difficulties associated with the disorder, investigators here concluded.
BRISTOL, England, Aug. 30 -- Autistic children have an impaired ability to place unfamiliar faces in memory, possibly explaining some of the social difficulties associated with the disorder, investigators here concluded.
Specifically, children with autism have difficulty with face identity aftereffect, the ability to fix in memory faces that are polar opposites of familiar faces, Elizabeth Pellicano, Ph.D., of the University of Bristol, and colleagues reported online and in the September issue of Current Biology.
The human brain seemingly has the ability to encode new faces in a "face space," Dr. Pellicano explained. Average or typical faces are in the center of the space. More distinctive faces lie toward the periphery, making them easier to distinguish from faces that are closer to average.
In people with normal face recognition abilities, she continued, the brain automatically places a new face in the face space on the basis of deviations from the average.
"The really neat bit is that the precise characteristics of what constitutes an average face are continuously updated based on our experiences in looking at other people," said Dr. Pellicano.
In the current study, the face identity aftereffect capabilities of 14 high-functioning boys with autism spectrum disorder were compared with those of 15 age- and ability-matched nonautistic boys (mean age about 11 years in both groups).
Scores on standardized tests showed the two groups had similar verbal and nonverbal abilities, but they differed significantly on the Social Communication Questionnaire (P<0.001).
The study participants were introduced to the faces of "Dan" and "Jim," who were described as "team captains." The boys then viewed computer-generated faces that resembled Dan or Jim to varying degrees. The two groups of boys demonstrated similar ability to place the new faces on Dan's or Jim's team.
The boys then viewed computer-generated faces that had features that were opposite those of Dan or Jim. After viewing these distinctly different faces, the normal boys substantially improved their ability to place faces that resembled Dan or Jim on the correct team. In contrast, the autistic boys showed little improvement in their aftereffect abilities (P<0.05 versus the normal group).
In the group of autistic boys, aftereffect scores had a significant correlation with Social Communication Questionnaire scores (r= -0.60, P<0.05). For the typically developing boys no significant correlation existed between aftereffect and the communication scores.
Dr. Pellicano and colleagues examined a subgroup of nine autistic boys with high social communication scores associated with more symptoms related to socialization, communication, and restrictive/repetitive interests. The boys' aftereffect was about one-third that of the typically developing boys (P<0.01).
Because the normal and autistic groups demonstrated similar precision for recognizing Dan-like and Jim-like faces, the investigators ruled out poor identification performance or task motivation as the cause of reduced aftereffect in the boys with autism. Moreover, the boys inspected the faces with a similar degree of intensity.
"Reduced attention to the adapting faces could potentially contribute to the weaker aftereffect in autism, and we see the relationship between adaptation and attention as a promising direction for future research," the authors stated.
Although face-reading difficulties might contribute to the social problems characteristic of autism, an early lack of interest in social phenomena could contribute to development of atypical face-coding mechanisms, they added.