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People with higher IQs filter out useless info faster, study finds

What distinguishes somebody with high intelligence quotient (IQ) scores, besides the annoying habit of finding a way to inject that fact into almost any conversation?

According to a new study from researchers at the University of Rochester, it could be their ability to ignore sensory information, specifically irrelevant information we take in with our eyes.

The study, released Thursday by the journal, Current Biology, found that people with high IQs were faster at telling whether an object that looks something like jailhouse bars was moving to the left or the right because their ability to filter out and dispense with useless input allowed them to focus more specifically on what was important.

The results, from the lab of neuroscientist Duje Tadin, were a surprise. Tadin and his co-workers were actually trying to explore another question when the results of a small pilot project with 12 people found the correlation between IQ and visual processing efficiency.

The correlation was so strong, Tadin suspected a statistical fluke. So his lab ran the study again, this time testing 53 people with a more rigorous version of a standard IQ test, and then asking them to tell whether the image was headed right or left. 

People with higher IQs, were much faster at the task.

“When we open our eyes, a huge amount of information lands there,” Tadin explained. “But only a small part of it is relevant. We don’t have the ability to process everything, so the brain focuses on the most important things, and ignores the less important.”

Vanderbilt University professor René Marois, who studies information processing and the brain, called the study significant. He has suggested that our brains are limited by traffic bottlenecks, akin to narrowing or merging freeways. Such bottlenecks can occur when one brain region is trying to communicate with another. So the brain needs to figure out what’s important and drop the rest from traffic flow to avoid a jam. 

“That’s why it’s so hard to multitask,” Marois said. “We can only pay maximum attention to one task, and if you try two tasks, we almost invariably become less efficient.”

Brains probably needed to develop this ability to survive. Animals walking in the jungle don’t need to focus on, and comprehend, every tree, bush or rock. They need to know if that small object moving up ahead is going to kill them, or if they can eat it. The faster you can do that, the better chance you have of living another day.

There may be ways to improve one’s ability to filter out unnecessary information, Tadin said, but he isn’t sure what such an exercise would look like. “Most so-called IQ enhancing exercises focus on how you process things that matter, not how to better suppress those that don’t,” he said.

He doesn’t think the test can or should be used to test IQ, though he thinks it may be a useful adjunct because it is free of the kinds of cultural biases that critics of IQ tests often highlight. It may also be useful for studies of people with reduced ability to suppress information, like those with depression, schizophrenia and the aged.

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Brian Alexander ( is co-author, with Larry Young Ph.D., of "The Chemistry Between Us: Love, Sex and the Science of Attraction," (, now on sale.