That magical number 7. Today I read Tufte's delightful rant about how PowerPoint destroys presentations. I recommend it highly, especially for those of you who often run meetings.Tufte attacks, among other things, the concept that one's audience can only remember seven (plus or minus two) items at a time, and that therefore one should limit the amount of information on a slide to that number. He references the famous 1956 paper by George Miller on the topic. I had never read that paper. Go take a side trip to read it now; it's drily witty and quite readable. Tufte points out that Miller's paper does not say “never present more than seven items at a time.” Instead, it says this: Let me summarize the situation in this way. There is a clear and definite limit to the accuracy with which we can identify absolutely the magnitude of a unidimensional stimulus variable. I would propose to call this limit the span of absolute judgment, and I maintain that for unidimensional judgments this span is usually somewhere in the neighborhood of seven. We are not completely at the mercy of this limited span, however, because we have a variety of techniques for getting around it and increasing the accuracy of our judgments. The three most important of these devices are (a) to make relative rather than absolute judgments; or, if that is not possible, (b) to increase the number of dimensions along which the stimuli can differ; or (c) to arrange the task in such a way that we make a sequence of several absolute judgments in a row. Want people to remember or understand more information? Then organize it.The discussion of recoding was also interesting, since recoding is an organization scheme we all use to understand and remember information. For instance, this brief blog entry is a terse recoding of Miller's paper. [Ceejbot]