Children with autism literally see shadows differently from their counterparts, a new study reveals.
While people can look at the shadow of an object and often figure out what the object is, shadows interfere with how autistic children recognize objects.
These new findings shed light on the sensory abnormalities that accompany and possibly even help cause autism, researchers added.
Growing body of research
Autism is thought primarily to impact how people function socially. However, a growing body of evidence suggests the senses are also affected in autism. For instance, past studies revealed people with autism are better at recognizing details and finding hidden figures within a larger picture, but are deficient at perceiving more complex stimuli — for instance, grainy pictures. Investigators have wondered if these anomalies might even cause some of the behavioral symptoms associated with autism.
One idea behind why these sensory differences exist is that autism results in a kind of noisiness in the way the brain perceives the world, making little details pop out more while masking the big picture. As such, investigating how autistic people deal with shadows might be interesting, scientists in Italy reasoned. Shadows can normally help people figure out the presence, number, relative position and identity of objects in a scene, but they also can obscure other details, functioning somewhat like noise does when it comes to perceiving sounds.
The researchers showed 20 high-functioning children with autism and 20 typical children computerized versions of familiar objects with recognizable shapes, such as apples, bananas, forks or knives. During these experiments, the presence, shape and position of the shadows the objects cast were systematically manipulated — for instance, a vase might cast the expected shadow, the shadow of a cone, or no shadow at all.
The children were asked to say when they recognized the object. When shadows matched the objects, children without autism were faster at figuring out what objects were, taking roughly 310 milliseconds on average compared with 340 milliseconds if shadows did not match objects and roughly 330 milliseconds if no shadows were present.
However, in autistic children, the presence of shadows — either matching or not matching the objects — interfered with recognition, making them take a little less than 350 milliseconds on average to do either. Instead, they reacted faster when there were no shadows present, recognizing objects in roughly 310 milliseconds. A possible explanation is that in autism, shadows go from being simple features worth a glance to extra details they hyper-focus on, potentially eating up their attention.
Very specific rules
During the course of the experiments, the children sometimes required snacks, and the researchers learned that autistic children typically have specific rules regarding food that should not be violated.
"For instance, in one case the child started screaming despite us giving him his preferred snack," said researcher Umberto Castiello, a neuropsychologist at the University of Padua in Italy. "We got very worried and asked the parents to enter the room. They entered and very calmly they said, 'Ah, OK, the snacks are not all of the same color!' For another case, same thing, same sequence of facts — the parents entered the room and said, 'Ah, OK, you did not present the snacks in a particular order.' Then, same thing with another child, and the parents said, 'Of course, the foods touch each other on the plate.'"
The findings regarding the shadows suggest that when one wants to teach children with autism, one might want to provide rooms with multiple light sources that minimize shadows, reducing distractions, Castiello said.
When it comes to better understanding the disorder, "we might be prompted to investigate the neural pathways connecting the object recognition systems with those systems devoted to the planning and organization of overt behavior, and how such pathways might be impaired in the autistic population," he added.
The scientists detailed their findings online in May in the journal PLoS ONE.