In recent days, I have been obsessively staring at telephone numbers. That is partly because I have just moved house and am flicking through my contacts list to send out change-of-address notes. But there is a second reason too: I have just stumbled on a fascinating little paper written by a Princeton cognitive psychologist called George Miller on the topic of “chunking”. And while this piece of research is half a century old, it has a curious relevance today - particularly in relation to those telephone numbers which are now so unthinkingly woven into the fabric of our 21st-century lives.

If Miller is correct, whenever we recite those digits, we unconsciously reveal the degree to which we are hardwired to sort information into mental boxes. And that trend has important implications - even (or especially) though most of us never give a moment's thought to the shape of those numbers.

The issue revolves around memory. Back in the early 1950s, Miller, like many psychologists and neuroscientists, was fascinated with the question of how brains retain information. Until that point, many scientists assumed that memory varied according to innate ability. However, Miller believed there was a more fundamental pattern. His research suggested that most people had a limit to how many pieces of data, such as numbers or letters, they could memorise when presented with a list. This usually ranged between five or nine data points but the average was “the magic number seven”.