Numbering wins

Understanding how our brains remember items on a list can be harnessed to boost memory.

- Marc Wilson

We've run out of milk and bread, so I'm going down to the supermarket to grab some. "We also need onions, and get some fish for dinner. Maybe some cereal and bananas for the boy," comes a shout from the lounge. And I need some star anise, too. I'm sure I can remember that.

This will be familiar to you all. A list sufficiently short that we tell ourselves we don't need to write it down, and research backs up our belief.

In a 1955 address to the US Eastern Psychological Association, American cognitive psychology researcher George Miller opined that he had, for seven years, "been persecuted by an integer". This whole number stalked him across his research and the data he routinely collected, and peeked out from the scholarly journals he read. Though it didn't always take exactly the same guise, it never changed, "so much as to be unrecognisable".

The title of the address was "The magical number seven, plus or minus two: Some limits on our capacity for processing information", so you can probably guess what that integer was.