Adults and children really don't see eye-to-eye, according to a new study.
The research reveals that kids under the age of 12 perceive visual information differently than adults do. While adults process different visual cues into one unified chunk of information, kids separate visual information. The childhood method of processing may allow kids to fine-tune their visual systems as they grow, the study authors say.
Researchers have long known that youngsters don't fully integrate sensory information until after about age 8. Before then, information received by touch, sight and hearing isn't as closely linked as the same information would be in the adult brain.
But the use of even one organ can provide multiple types of information. In the case of vision, people perceive depth based on several cues, including binocular disparity (small differences between the images produced by each eye) and texture (nearby things are more detailed).
To find out how this information is integrated, scientists at University College London and Birkbeck, University of London asked children and adults to wear 3-D glasses and compare images of two slanted surfaces to judge which was the "flattest." Images presented the participants with texture and binocular information either separately or at once.
While adults were more accurate in their responses when they got both pieces of visual information together, kids weren't, at least not kids under 12. Beyond age 12, children combined both types of information to improve their accuracy. The findings imply that adults combine different kinds of visual information into a single unified estimate, while children do not.
Adult accuracy comes at a cost, however. Once sensory information is combined, it cannot be untangled again, according to the researchers. To find out whether kids were able to avoid this "sensory fusion," the researchers showed the adults and children 3-D discs in which perspective and binocular information sometimes disagreed. For instance, in some images the parts of the disc that appeared farthest away also showed the most details.
Adults proved bad at determining whether the slant of these discs was the same or different from comparison discs, because the conflicting information confused their visual system.
Six-year-olds, on the other hand, had no trouble spotting the differences, which suggests young children can perceive the information separately.
Overall, the children seemed to use the first visual cue their brain processed to make their judgments in the experiments. That made them less accurate than adults, but it improved their speed. Since kids have slower processing speeds than adults, this quick-and-dirty approach may help them keep up while their brains learn to integrate information. It may also allow for tweaks in the system as the face grows, changing the distance between the eyes and the visual information the brain receives.
The researchers hope to use brain-scanning techniques to find out how changes in the brain coincide with these perceptual shifts.
"Babies have to learn how different senses relate to each other and to the outside world," said study co-author Denis Mareschal of the Center for Brain and Cognitive Development at Birkbeck in a statement. "While children are still developing, the brain must determine the relationships between different kinds of sensory information to know which kinds go together and how. It may be adaptive for children not to integrate information while they are still learning such relationships."
The research is detailed in the Sept. 13 issue of the journal Proceedings of the National Academy of Sciences.
