Field of Science


You Might Have Outgrown Synesthesia as a Kid

Feeling smug because your normal brain doesn't insist on coloring all its 2's blue and M's purple? Not so fast: you might have been a child synesthete. Some elementary schoolers have associations between colors and letters or numbers that fade as they age. Others' associations expand to take over the whole alphabet, leading them toward a rainbow-hued adult life.

Studying kids with synesthesia is tricky, because first you have to find them—and at a young age, kids don't know the word, or that their perceptions aren't standard. University of Edinburgh psychologist Julia Simner screened 615 kids for synesthesia back in 2009. Starting with six- and seven-year-olds, Simner and her coauthors sat the kids in front of a computer screen and told them to play a game: they'd see a letter or number next to a set of colors, as above, and should choose the "best" color for each one.

After the computer ran through every letter and numeral in random order, it paused for several seconds, then did the entire test a second time. Forty-seven of the kids were significantly consistent in their choices between the two tests—which meant either that they were synesthetic, or that they had a good memory for colors they'd picked at random. The moment of truth came a year later, when those 47 kids sat down and took the test again. People with synesthesia should be consistent not only over a few minutes, but over years. That's because it's not really a test of memory for them; color is simply a quality that a letter or number has, like being even or a consonant. (For rarer types of synesthesia, people might experience colors with sounds, or tastes with words.)

In 2009, Simner found eight girls and boys who passed her tests. For a new study published in Frontiers in Human Neuroscience, Simner and coauthor Angela Bain returned to these patient elementary schoolers—now 10 or 11 years old—and did the test a third time.

They wondered whether any kids' synesthesia would have faded over the intervening years. Anecdotally, some adults say they remember having synesthesia as a child and growing out of it. The researchers started with not just their eight synesthetes, but 39 of the kids who had been classified as near misses in the first go-around—they had been consistent over 10 seconds, perhaps, but not over a year, or their performance had been just shy of statistically significant. Another 40 average kids served as controls.

This time, six kids passed the test. They were consistent both within two trials and compared to their original tests four years earlier. On testing day, these synesthetes made consistent color choices for about 26 out of the 36 letters and numerals they saw. Non-synesthetes were consistent for only 6 or 7.

Five of the children were from the original batch of synesthetes, and the sixth had been a near miss originally. The other three original synesthetes were no longer significantly outperforming their peers in choosing consistent colors. This may be evidence of "synesthetic demise," the authors write.

Young synesthetes losing their colors over time would fit with a popular theory about synesthesia, which says that it comes from an overly connected brain. "All very young children have hyper-connected brains," Simner says; the neurons branch out indiscriminately between different areas. As we grow, the unneeded connections are pruned away, a process that continues throughout childhood. "It may be that synesthetes escape the pruning, so to speak," Simner says. All kids might start out with some degree of synesthesia, which fades away with normal development.

It's also possible, Simner says, that the "near-miss" kids actually had synesthesia that was developing more slowly than their peers'. She found that synesthetes add more and more colored characters to their rosters as they age. When synesthetes were six or seven years old, they had consistent colors for only about a third of letters and numbers. In another year that number had risen to almost half, and at age 10 or 11 over 70% of letters and numbers had fixed colors. Adult synesthetes have consistent colors for 80 to 100% of letters and numbers.

So for people who don't lose their synesthesia as they age, it becomes steadily more consistent. Now that Simner's subjects are 14 and 15 years old, she says, "we very much hope" to test them again. The teenagers may be happy to learn that at least one thing about their lives is becoming less chaotic.

Image: Simner & Bain 2013.

Julia Simner, & Angela E. Bain (2013). A longitudinal study of grapheme-color synesthesia in childhood: 6/7 years to 10/11 years. Frontiers in Human Neuroscience DOI: 10.3389/fnhum.2013.00603

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