Kids whose frustrated parents ask them “can’t you control your behavior?”
may be telling the truth when they say no, new research out of the University of Oregon shows.
Researchers in the University’s Institute of Neuroscience studied the eye movements of 41 people aged 4 to 29 and found that young children are incapable of ignoring objects in their peripheral vision, even when they are told to, according to a press release.
Human physiology professor Paul van Donkelaar, who led the study and spoke about the results at a symposium in Sydney, Australia, on Aug. 16, said the results of the study contribute to
knowledge of how the portion of the brain that controls behavior develops.
In the study, subjects were given two tasks involving looking at a target on a screen in a dark room. In the first trial, subjects were told to look at any secondary targets that flashed in their peripheral vision. In the second, they were told not look at anything but the main target. Despite being repeatedly reminded not to look at the secondary targets, young children had great difficulty not looking, van Donkelaar said.
Movement of the eye occurs when the cerebral cortex decides when to move the eye and what to look at, then sends a signal to the brain stem, which tells the eyes to move. In young children, the brain stem tells the eyes to move without the proper signals from the cortex, van Donkelaar said.
Researchers discovered that the eye movement without signals from the cerebral cortex means children’s initial response to the secondary targets was very fast, but inaccurate, producing a high level of “multiple saccades,” which are rapid eye movements toward a secondary object, in young children.
Normally a saccade is very fast – between 10 and 30 milliseconds – but the youngest subjects were moving their eyes much faster than normal 20 to 30 percent of the time, he said. Multiple saccades are produced when the eye’s initial movement is so fast that it is inaccurate. The eye misses the target the first time and must move again in order to see the
object, van Donkelaar said. He said that because the multiple saccades occurred mostly in trials where the children were told to look at the secondary object, young kids are not in control of their response.
“This is a very simple task that fits into everyday life. Kids may not be in control of their behavior.” he said, “they make decisions to look at things without thinking about it first.”
In older children and adults, the cerebral cortex has developed fully and catches up with the rest of the body, giving healthy people control over their movements and behavior, he said.
This study has potential to be used to help diagnose developmental disorders, including ADD, but the research is especially significant in the study of cerebral palsy, a condition in which the cerebral cortex is delayed into adulthood, van Donkelaar said.