The absent-minded professor is a classic image: someone who's lost in deep thoughts all the time but pays very little attention to what's going on right in front of them. There may be a little something to that cliché (if only just a little) if a study published this week in Current Biology is to be believed. The study showed that IQ scores, an imperfect measure of general mental faculties, correlated with their tendency to ignore an image that may be mistaken for background visual noise.

The results are a bit easier to understand than the interpretation, so we'll start with those. The visual tests all involved a pattern of dark bars on a light background that would move to either the left or right. The study participants were asked to determine which way they were moving, and the researchers timed how long it took. During the same experiments, the participants were given a standard IQ test.

The key feature of the work was that the size of the image—the degree to which the grey bars filled the screen—varied during the tests. In some cases, the bars filled most of the screen, while in others they covered only a small portion directly in the middle.

The researchers found that when the image was small, the IQ scores generally correlated with a quick response—the higher your score, the faster you could pin down the direction of motion. This, the authors surmise, is probably related to the ability to bring focus to tasks. But when the target image was bigger, the exact opposite happened. Here, the higher the IQ score, the longer it takes for someone to recognize which way the pattern is moving.

This, the authors suggest, is also a product of people's ability to focus. When an image takes up most of the screen, it can usually be dismissed as a background, and thus as little more than a distraction that's vying for your attention. So in this view, people who are better at IQ tests are better at filtering out distractions and therefore are more likely to ignore the big image as nothing more than background. As a result, it takes them longer to focus enough to actually register what it's doing.

So why would this be the case? Lots of studies have shown that people have limited cognitive resources. In many cases it doesn't matter; the cognitive resources involved in having an annoying song running through your head are probably different from the ones needed to solve differential equations. Sometimes, though, you can find things that tax the same bits of your brain—for example, you might not be able to recite the song's lyrics as you solve the equations.

Although we think of this in terms of ignoring background distractions and focusing on a task, the authors suggest that what we're really seeing is two things competing for the same mental resources in a brain's visual processing system. One of them is trying to figure out what our conscious brain needs to be aware of and what it can ignore. That's sharing time with whatever part of the brain is trying to identify motion in the scene. In this view, those who score higher on IQ tests tend to give more time to the process that filters out background visuals that we don't have to distract our conscious thoughts with.

So if you forget to notice something like your significant other's new haircut, can you safely conclude that it's okay because it just means you've got a high IQ? Maybe. These are just general tendencies and there's lots of variability among individuals, even if they collectively show a clear trend. And that's without even getting into the value of the aspect of intelligence measured by the IQ score.

Current Biology, 2013. DOI: 10.1016/j.cub.2013.04.053 (About DOIs).