Consider, for example, the fact that people who use computers touch the machine a lot. Whether through a mouse, keys, joy stick, or touch screen, many people have more physical contact with computers than they do with other people. Moreover, you can now wear computers -- in your shoes, shirt pocket, or belt, for example. Wearable computers, especially when they become as common as underwear, will have unusual opportunities to get to know you in a variety of situations. They could have access to your muscular tension, heart rate, temperature, and so on. Instead of being restricted to perceiving only your visible and vocal forms of affect expression, they could get to know you intimately - or as well as you will permit them to. At this point, they will also, like underwear, probably cease to be shared and will become truly personal computers.

Suppose you have too much stress in your life and your doctor suggests that you learn to relax more. Your wearable affective computer could help you learn what events cause you stress and figure out ways to reduce it. While you are engrossed in playing with the kids, your affective wearable might whisper in your ear, "see how relaxed you are now." A little feedback device you could turn on or off might not only help reduce stress-related disorders, it might also assist in gathering important medical research data or helping patients in recovery. The key to the wearable computer is its constant presence; it is not limited to gathering data in the lab or doctor's office, but can get to know your range of responses during the daily routine.

Affective information could also be communicated in unconventional ways. Imagine that your wearable computer could detect the lilt in your walk as you leave the office and broadcast it to your spouse -- encoded, of course (lest a salesperson learn of your happiness and take this auspicious opportunity to telephone you). The result would be a sort of "mood ring" that alerts you to your spouse's affective state -- one that is more accurate than the dime-store temperature sensors once advertised on late-night television.

Applications of affective recognition could extend to entertainment as well; for example, interactive games might detect your level of fear and give bonus points for courage. When we measured the responses taken of a student playing the computer game DOOM in our lab, we expected the electromyogram of jaw clenching to peak during high-action events -- such as when a new deadly enemy starts an attack. However, the biggest peak -- and it was significantly higher than the others recorded -- occurred when the student had trouble configuring the software! (See figure 13.4.)

What if software companies could obtain similar affective information about people interacting with their products? Unlike questionnaires, an affect-sensing computer could identify the parts of the software that provoke the greatest annoyances and those that produce the greatest pleasure. Not only would the timing of affective responses be easier to relate to specific causes, but they would tend to capture product qualities that are hard to put into words. All makers of environments -- architects, automobile manufacturers, software designers, decorators, hotel managers -- benefit from learning how people feel when they are in their spaces.

Computers coupled with suitable sensors and pattern-recognition algorithms should soon be able to recognize the basic affective states of a willing individual in a typical context. The emphasis on willing participant here is important. Measurements of affective states obtained in an underhanded manner are not likely to be accurate. People who want to deceive such systems will probably succeed. One fellow, for example, managed to fool a polygraph by putting a thumbtack in his shoe under his big toe; he stepped on it every time he was questioned in a particular way. Affective information will be most accurate, and useful, when it is willingly communicated, presumably for the mutual benefit of everyone involved.