By Richard Day in The Conversation.
The last time you went to see a doctor, it was probably because you were in pain – it’s by far the main reason people access the health service. And if you did go because of pain, your doctor probably asked you to rate it on a scale from zero to ten. Zero being no pain and ten being the worst pain you can imagine. This pain scale is so simple and intuitive, that it’s hard to imagine a time when doctors didn’t have it.
Before World War II, measuring pain mainly focused on how much a specific stimulation would be needed to elicit a pain response. This is the so-called pain threshold, the point at which an external stimulus changes from a non-painful sensation to a painful one. For example, increasing pressure is applied to the skin until the subject reports feeling pain. Early psychologists also explored pain tolerance, where a painful stimulus would be applied and the duration a person could withstand the pain would be measured. But neither of these measured the nature or intensity of pain.
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