The Magical Number Seven, Plus or Minus Two

There are some core concepts about how minds work that are reasonably important, whether you’re developing an interface, writing, or just trying to work more effectively with yourself or others.

I first ran into The Magical Number Seven, Plus or Minus Two quite some time ago, and it’s influenced my approach to many things over time.  I just happened to run across the above link to an online version, so I figured I’d include it here.

“My problem is that I have been persecuted by an integer. For seven years this number has followed me around, has intruded in my most private data, and has assaulted me from the pages of our most public journals. This number assumes a variety of disguises, being sometimes a little larger and sometimes a little smaller than usual, but never changing so much as to be unrecognizable. The persistence with which this number plagues me is far more than a random accident. There is, to quote a famous senator, a design behind it, some pattern governing its appearances. Either there really is something unusual about the number or else I am suffering from delusions of persecution.”

Although of course there’s no substitute for actually following the link and reading the whole thing, the upshot of this is that most people can manage to keep seven discrete items in their mind simultaneously, although some folks can deal with as many as nine, and others as few as five.

This has an immediate impact on a lot of things.

If you’re dealing with a large number, for example, it’s easier for people to memorize it (or even retype it correctly) if you break it into chunks of five digits or smaller.  Think phone numbers, credit card numbers, social security numbers.

A core NLP model is the concept of “chunking” information.  How we deal with large amounts of data is to “chunk up” to higher levels of hierarchy, or “chunk down” to specific details, allowing us to work with an amount of discrete items that is comfortable for us (5 - 9). 

For example, a “general chunk” item is a forest.  This can be broken into smaller chunks (grove, stand, tree, limb) until we come to a “specific chunk” item, a leaf.

Different people have different default learning strategies that they are comfortable with, in different contexts.  Some people use a “general chunk” strategy where they prefer to get the big picture first, and then dive in and look at specific details as they gain familiarity.  Other people favor “chunk specific”—they don’t want to talk about “forest” until they’ve got a handle on “leaves”.

Understanding these strategies begins to allow flexibility—if you’re the “chunk specific” type, you can “try on” a general chunk strategy if that’s the way a specific piece of material is presented to you.  Likewise, if you’re attempting to teach a group, you can alternate between general and specific chunk material as necessary to keep everyone in the group learning comfortably.

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