People with higher scores on intelligence tests are better able to filter out unnecessary background distractions, according to researchers who report the brains of people with high IQs filter out non-essential information better than average.

In the study conducted by a team at University of Rochester, 53 people were given a simple visual test (see below) that asked them to identify the directional movement of black and white lines. The exercise measured unconscious ability to filter out visual movement. Some images were small and filled only the center of the screen, while other clips were much larger. The test subjects were asked to simply state whether the lines were moving to the right or left. Each study participant was also given a standard intelligence test.

The researchers found that the people with the highest IQ did the worst at detecting any movement on the larger clips and noticed movement on the smaller images faster than participants with lower IQ scores.

Based on previous studies, researcher Michael Melnick of the University of Rochester, said the results were not surprising.

"From previous research, we expected that all participants would be worse at detecting the movement of large images, but high IQ individuals were much, much worse," he said in a statement.

Using the example of driving a car or walking down a hallway, the researches explained in most cases, background movement is less important than small moving objects in the foreground. "That counter-intuitive inability to perceive large moving images is a perceptual marker for the brain's ability to suppress background motion," the researchers wrote.

As a person's IQ increases, their ability to concentrate on the foreground and filter out distracting background motion also increases.

An earlier study of 12 people found a 64 percent correlation between motion suppression and IQ scores and the University of Rochester study found the correlation in 71 percent of the 53 people studied.

"We know from prior research which parts of the brain are involved in visual suppression of background motion. This new link to intelligence provides a good target for looking at what is different about the neural processing, what's different about the neurochemistry, what's different about the neurotransmitters of people with different IQs," said Duje Tadin, a senior author on the study.

"Because intelligence is such a broad construct, you can't really track it back to one part of the brain," Tadin said. "But since this task is so simple and so closely linked to IQ, it may give us clues about what makes a brain more efficient, and, consequently, more intelligent."

The researchers also said that the new vision test could remove some of the limitations associated with standard IQ tests, which have been criticized for cultural bias.

"Because the test is simple and non-verbal, it will also help researchers better understand neural processing in individuals with intellectual and developmental disabilities," said co-author Loisa Bennetto.