Finding your brain's spam filter

And while the capacity of our email inbox is limited only by disc space, our mental 'inbox' of working memory is much more constrained. In fact, several decades of research have indicated that our capacity to hold information “in mind” for immediate use is limited to a mere three or four items. Moreover, just as people vary in height and eye color, we also vary in the capacity of this memory inbox. Interestingly, these differences in working memory capacity are strongly predictive of a person’s ability to perform abstract reasoning, mathematics, and other forms of complex problem solving. This relationship between memory capacity and fluid intelligence has motivated many scientists to try to understand why and how people differ in this important cognitive ability.

Scientific American