The number of things you can hold in your mind at once has been traced to one penny-sized part of the brain.Two research teams operating independently using different techniques have come to the same conclusion: that this "Short Term Working Memory" is implemented by one small section of the brain, in Humans anyway.
The finding surprises researchers who assumed this aspect of our intelligence would be distributed over many parts of the brain. Instead, the area appears to form a bottleneck that might limit our cognitive abilities, researchers say.
"This is a striking discovery," says John Duncan, an intelligence researcher at the Cognition and Brain Sciences Unit in Cambridge, UK.
Most people can hold three or four things in their minds at once when given a quick glimpse of an image such as a collection of coloured dots, or lines in different orientations. If shown a similar image a second later, they will be able to recognise whether three or four of these spots and lines are identical to the first set or not.
But some people can only catch one or two things in a glance, while others can capture up to five.
This very short-term memory capacity is thought to be related to intelligence. In the same way that a computer with a larger working memory can crank through problems more quickly, people with a greater capacity for holding images in their heads are expected to have better reasoning and problem-solving skills.
Such a "Short Term Working Memory" is essentially the same as a "Cache" in Computer Science terms. For example, your browser has a "Cache" of recently-visited sites and images, so that if you hit the foward and back buttons rapidly, the data doesn't have to be retrieved again over the Internet, it's available quickly.
What does this mean for research on Intelligence? Bugadifino, as they say in the Classics. But it's a significant step in the journey to a better understanding of how our minds work.