From time to time I witness the wide gap between theory and practice in the field of interaction design and information architecture. I often witness this when simpletons (those who take a non-theoretical and non-scholarly approach to everything in life because they always think everything is black and white) attempt to practice what should be left to those who are better educated. This often comes in the form of misapplying good research findings to areas of practice for which it was never intended.
Ask any information architect or interaction designer and they will undoubtedly tell you that they have heard of “the magical number 7 +-2” principle. However, despite its wide use and popularity, I’ll bet that few would be able to tell you the origins of it. The idea comes directly from a 1956 research study by the cognitive scientist George Miller. In his study, he suggests that the capacity of short-term memory is within the range of 5-8 items. Miller was primarily writing about short-term memory span for digits, but an item could include something more complex such as a long word. He also introduced the idea of “chunking” which means we are able to group similar items together to form one item (such as a string of letters to form one word).
Other studies have been conducted since then that suggest that the capacity for short-term memory is much less. Also other studies suggest that the capacity may vary depending on the type of information (visual, spatial, phonological). What also complicates matters are issues of interference and attention.
The reason why applying such research to the practice of design and information architecture could be dangerous is because there are so many confounding variables in a real-world environment. This is, of course, assuming that the principles were applied correctly. However, the findings of Miller’s research study is often misapplied, as is apparent when some designers and information architects say things like . . . “because people can only hold 5-9 items in short-term memory, I decided that there should only be 7 menu items on this website, or 7 icons, or 7 bulleted items in a category, or 7 subdivisions on the homepage . . . ” and on and on and on. What does Miller’s study have to do with the number of tabs on the top of a web page? Such practices are not the implications of his study! Please spread the word.