Photograph by John Clark
Imagine for a moment a weather service that uses lots of lookouts, each of whom takes one measurement. Then all of them call in their results to a central phone exchange at once. One specialist reports whether it’s hot, another whether it’s cold, another whether it’s windy, and so on. To save time and money, each lookout indicates the severity of the condition being monitored by the number of times he lets the phone ring before hanging up. For example, one ring signals a light breeze and five rings a tornado. At the central exchange, a forecaster determines the overall conditions by monitoring the collective ringing of all the phones. That, in essence, is your brain analyzing your skin. One set of sensors reports cold, another warmth, another pain, and so forth. As you are about to discover, separate skin sensors sometimes get their lines crossed.
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