Individuals with autism spectrum disorders (ASD)
tend to stare at people’s mouths rather than their eyes. Now,
an NIH-funded study in 2-year-olds with the social deficit disorder
suggests why they might find mouths so attractive: lip-sync — the
exact match of lip motion and speech sound. Such audiovisual
synchrony preoccupied toddlers who have autism, while their unaffected
peers focused on socially meaningful movements of the human body,
such as gestures and facial expressions.
"Typically developing children pay special attention to human
movement from very early in life, within days of being born.
But in children with autism, even as old as two years, we saw
no evidence of this," explained Ami Klin, Ph.D., of the Yale
Child Study Center, who led the research. "Toddlers with autism
are missing rich social information imparted by these cues, and
this is likely to adversely affect the course of their development."
Klin, Warren Jones, and colleagues at Yale, report the findings
of their study, funded in part by the National Institute of Health’s
National Institute of Mental Health, online March 29, 2009 in
the journal Nature.
For the first time, this study has pinpointed what grabs the
attention of toddlers with ASDs," said NIMH Director Thomas R.
Insel, M.D. "In addition to potential uses in screening for early
diagnosis, this line of research holds promise for development
of new therapies based on redirecting visual attention in children
with these disorders."
A eureka moment in the research came when researchers followed
up on a clue from children’s responses to audiovisual synchrony
embedded in a nursery rhyme cartoon.
While it was known that people with autism do not spontaneously
orient to social signals, it was unclear what early-emerging
mechanism may contribute to that. Nor was it clear exactly what
they were attending to instead. To find out, Klin, Jones and
colleagues tracked the eye movements of two-year-olds with and
without the disorder while they looked at cartoon animations
on split-screen displays.
The researchers borrowed a technique from the video game industry,
called motion capture. They then reduced the movements to only
points of light at each joint in the body, like animated constellations.
These cartoons played normally — upright and forward — on one
half of the screen, but upside-down and in reverse on the other
half. The inverted presentation engages different brain circuits
and is known to disrupt perception of biological motion in young
children. The normal soundtrack of the actor’s voice, recorded
when the animations were made, accompanied the presentations.
Eye-tracking data initially showed that 21 toddlers with ASD
had no preference for the upright animations, looking back and
forth between the two. By contrast, 39 typically-developing toddlers
and 16 developmentally delayed but non-autistic toddlers clearly
preferred the upright animations.
However, responses to one animation didn’t fit the pattern.
The toddlers with ASD changed their behavior and shifted their
attention to the upright figure as it played a game of pat-a-cake,
where the figure claps his hands repeatedly. In this animation
(see movie below), unlike the others, the movements of the points
of light actually cause the clapping sound. This physical synchrony — dots
colliding to produce a clapping sound — only existed on the upright
side of the screen, because the inverted figure played in reverse
and its motions weren’t in sync with the soundtrack. The children
with ASD chose the upright figure 66 percent of the time, a strong
This clue led the researchers to suspect that what initially
appeared to be random viewing by the ASD toddlers might actually
reflect preference for audiovisual synchronies that were less
obvious than the clapping. So they re-analyzed the data, factoring
in more subtle synchronous changes in motion and sound.
"Audio-visual synchronies accounted for about 90 percent of
the preferred viewing patterns of toddlers with ASD and none
of unaffected toddlers," said Jones. "Typically-developing children
focused instead on the most socially relevant information."
A follow-up experiment using new animations optimized for audiovisual
synchrony confirmed these results.
Klin, Jones, and colleagues also recently reported (http://www.nimh.nih.gov/science-news/2008/lack-of-eye-contact-may-predict-level-of-social-disability-in-two-year-olds-with-autism.shtml)
that children with autism look more at peoples’ mouths than eyes
as early as age 2. Since the mouth is the facial feature with
most audiovisual synchrony — lip motion with speech sound — the
researchers propose that their new findings offer a likely explanation
for this phenomenon.
"Our results suggest that, in autism, genetic predispositions
are exacerbated by atypical experience from a very early age,
altering brain development," said Klin. "Attention to biological
motion is a fundamental mechanism of social engagement, and in
the future, we need to understand how this process is derailed
in autism, starting still earlier, in the first weeks and months
NIMH is funding a related research project of Klin and Jones’ that
explores related behaviors in infants who have older siblings
already diagnosed with ASD and who, because of the genetic heritability
risk in autism, have greater risk of also developing the condition.
Also participating in the research were: David Lin, now at Harvard
Medical School; Phillip Gorrindo, now at Vanderbilt University;
Gordon Ramsay, Ph.D., Haskins Laboratories. The study was funded
through the NIH’s STAART Program (Studies To Advance Autism Research & Treatment).
Eye-tracking data shows where toddlers in each of three groups
were looking during the Pat-a-Cake animation. It plays upright
and forward on the left side of screens, upside down and in reverse
on the right side. Red cross indicates where the child was looking.
Toddler with autism is focused on audiovisual synchrony of hands
clapping, while typically developing and developmentally delayed
toddlers focus on face.
Pat-a-cake animation, with audio playing at half-speed and
color scale indicating levels of audiovisual synchrony in child
with autism. The hands clapping show the highest levels of audiovisual
synchrony (red) in the figure on the right, which played upright
and forward. Motion was out of sync with the sound track in the
figure on the left, because it played upside down and in reverse.