People frequently complain that they can’t remember things — and they wish their brains had more storage capacity, like today’s ever-expanding computer hard drives and RAM. If we could just improve the sheer size of our memory, we’d be able to retain and manipulate more data, and we’d become smarter and smarter — right?

Not according to an intriguing new experiment by brain scientists at the University of Oregon. Edward Vogel and a team of students took a handful of volunteers and tested their “visual working memory” — their ability to maintain awareness of events and objects around them. The test asked them to pay attention to red or blue bricks in a visual picture.

Now, visual working memory is highly correlated to intelligence: People with a bigger VWM tend to score much better on an array of cognitive challenges. For years, scientists have assumed that VWM is roughly analogous to cramming info into your head: The more you can fit in there, the smarter you are.

But when Vogel mapped the brain-wave activity of the volunteers, he noticed something much weirder. The people with the largest capacity in their VWM weren’t retaining tons of information. No, they were being quite selective. Their genius lay in being able to strip out inessential information: To pay attention only to the red bricks — to hold only those “in mind” — and to ignore the blue ones. The upshot, as the editors at Nature summarize, is that …

… this also implies that an individual’s effective memory capacity may not simply reflect storage space, as it does with a hard disk. It may also reflect how efficiently irrelevant information is excluded from using up vital storage capacity.

That chart above shows this relationship: The more efficiently the subjects’ brain worked, the bigger their memory capacity. This is not to say that people who can’t screen out stimuli are dumber. As Vogel noted, “Being a bit scattered tends to be a trait of highly imaginative people.” The more you rattle the marbles around in your brain, the more creative new connections you make, as it were — connections that might be lost on those focusing intently on just the red ones.

(Thanks to the Book of Joe for this one!)