“Perfect Circles: Why We Can Spot Them, But Can’t Draw Them” by Rachel Nuwer

Article featured in BrainDecoder

“(…) Most people can quickly pick out an imperfect circle, but the ability to draw a perfect one freehanded seems to elude all but the legendary Giotto and similarly accomplished masters. This is because the seemingly complimentary tasks of recognizing imperfection and then correcting it to produce perfection actually have little to do with each other—at least so far as our brains are concerned. While the visual cortex handles image processing involved in detecting off-kilter spheres, completely different parts of the brain responsible for coordination and fine muscle control, combined with the complexity of the arm’s structure, are to blame for our inability to draw a perfectly round sphere.

(…) “The majority of us don’t have a lot of practice in drawing, but we all do have a lot of practice in identifying complex stimuli,” says Rebecca Chamberlain, a postdoctoral researcher in the laboratory of experimental psychology at the KU Leuven in Belgium. (…)

To pull off processing immense amounts of information—from the smallest nuances in an image to the convergent big picture—our visual cortex is organized in a hierarchical fashion(…) The primary visual cortex, the first brain area to process pixel-like input coming from the eyes, has a precise map of the retina and is highly specialized for detecting patterns, thanks to groups of neurons that each tune in to a certain visual feature. Some, for example, detect edges, such as a bright line on a dark background, while others pick up on small differences in orientation and color. In higher visual areas, others still respond to curvature, ultimately processing circles and other curved shapes.

(…) All of that extra effort takes a toll, as evidenced by the fact that, when people are asked to speed up their circle drawing, the resulting figures precipitously decline in symmetry. Other studies have shown that, when asked to produce horizontal, straight lines—an easier shape than circles— people draw lines that tend to deviate diagonally up or down, and the effect is amplified when subjects are asked to simultaneously think about something like simple math problems. In both cases, deterioration of drawing quality seems to correspond with a slackening of the elbow as people let their brain revert to a simpler, shoulder-driven formula for coordination. “The brain doesn’t have enough resources to focus on corrections of movement and do cognitive tasks at the same time,” Dounskaia says.

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