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Cover Quote: February 2000

That people have a single locus of attention is not always a drawback. Magicians exploit this characteristic shamelessly. A good magician can fix the attention of an entire audience on one hand so that not a single spectator will see what the other hand is doing, although that hand is in no way concealed. If we know where the user’s attention is fixed, we can make changes in the system elsewhere, knowing that the changes will not distract the user. This phenomenon was exploited in designing the Canon Cat. When a user stopped working, the Cat stored a bit-for-bit image of the screen—exactly as the display appeared when she stopped—on the first track of the disk. When the user again loaded her disk, the Cat placed the most recently viewed image on the screen, in only a fraction of a second. It takes about 10 seconds for a person to switch contexts or to prepare mentally for an upcoming task, but it took only 7 seconds for the Cat to read into memory the rest of the disk. So while the user was staring at the static screen image, recalling what she had been doing and deciding what she was going to do next—her locus of attention being the preparations for the coming task—the system finished loading. Only then did the screen become active, although it did not change appearance, except that the cursor began to blink. Only a handful of users ever noticed this trick. Most Cat owners thought that the product magically managed to read in the whole diskette in the fraction of a second that it took to display the first screen. Presto!

- Jef Raskin
The Humane Interface: New Directions for Designing Interactive Systems, 2000
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