Azure, teal or cornflower: Infants instinctively seem to know that these are all shades of blue, just as they can categorize avocado and lime as greens and crimson and maroon as reds. However, the brain shifts responsibility for this recognition just from learning the names of these broad categories of colors, a new study reveals.
The findings suggest that two forms of color-category processing may exist: a word-based form centered predominantly in the brain’s left hemisphere and a nonverbal form centered in the right hemisphere. According to the hypothesis, learning the words for color categories triggers the switch from using the right hemisphere to the left.
For the study, Anna Franklin of the University of Surrey in the United Kingdom and a team of collaborators from the University of California, Berkeley, and the University of Chicago researched the reactions of 37 children, ages 2 to 5. The scientists divided the children into two groups based on their ability to understand and correctly name colors. The 18 who qualified as “namers” could accurately identify color categories such as blue and green; the other 19 were dubbed “learners.”
Both groups of children looked at a colored target placed in either their left or right visual field. Sometimes, the target belonged to the same color category as the background. Other times, the colors came from different categories, although the absolute difference in hue—or shading—remained the same. In each trial, the researchers measured the time the child required to initiate an eye movement toward the target from a central fixation point.
Like adults, the children were faster at detecting targets on different-category backgrounds than on same-category backgrounds. The namers and learners also showed about the same speed in recognizing targets.
But the side of the brain that conferred the different-category advantage varied. Namers were quicker in responding to different-category colors shown to the right visual field, reflecting activity in the brain’s left hemisphere. Learners showed the enhanced effect of different categories only when discriminating colors in the left visual field, a sign of activity in the right hemisphere. In other words, the learners’ brain activity resembled that of infants before they acquire language. The namers showed the same left-brain advantage observed in adults.
“This work shows that learning a word for a color changes the way in which the brain categorizes color,” Franklin says. The work appears in the Nov. 25 issue of the Proceedings of the National Academy of Sciences.
This research “furthers our understanding of how color categorization changes as young children learn color words,” says psychologist Jonathan Winawer of Stanford University. Says Richard Ivry, a professor of psychology and neuroscience at the University of California, Berkeley, who was not involved in the research: “Once linguistic categories develop ... people are faster at perceiving color differences in the right visual field, presumably because language facilitates decision processes,”
To look for other similar effects, Franklin plans to investigate other category systems, such as emotions or animals.