They could only watch as their children slipped away.
He just looked like he wasn't there anymore," one mother said.
"Loss of speech, loss of eye contact, loss of socialization," said another.
He would just turn and face the wall," said Tonya Mirtes, whose son, Daniel, has autism.
Could robots crack the autism code?
"Just with this robot, it was able to keep him engaged," Tonya Mirtes said.
"You shoot hoops, and if I'm stressed out, then it will slow down," Daniel Mirtes said.
It sometimes looks like 16-year-old Daniel playing basketball, but he's actually hooked up to a robot. Daniel's heart rate, skin temperature and muscle movements are recorded. From that, the robot reads and responds to his mood.
"If the robot determines that the child is getting stressed out, the robot will change, for example, the speed of the game, may play relaxing music," said Nilanjan Sarkar, PhD, of the departments of Mechanical Engineering and Computer Engineering at Vanderbilt University in Nashville, Tennessee.
"The amazing thing is you can put it all together and learn what a child is feeling," said Vanderbilt Medical Center's Wendy Stone, PhD, a clinical psychologist and professor of pediatrics.
The robot helps humans understand what causes anxiety and calmness, something autistic kids can't put into words.
"If we can adapt our behavior, we're going to have much more success," Stone said.
Researchers found robots predicted the child's emotional state correctly more than 80 percent of the time. The robot was about as good at identifying a child's feelings as an experienced therapist. Robots helping humans understand autism.
Researchers believe the robots work well for children with autism because they are more predictable and consistent than humans. They are working on creating a smaller version of the robot so that parents can work with it at home.