In the mid 1980s, there was a PBS documentary series called “The Body Human” (I think) that had a whole episode on pain. Apparently, we do not experience our bodies directly; our experience them is mediated through a mental model of the body. It is through this construct that our minds interpret pain messages, and it is through this mental construct that people with amputated limbs experience the sensation of phantom limbs. The nerve endings are still there in a severed limb, but the mind interprets this information in terms of it’s old mental constructs. When the person’s image of his body is revised and corrected, the phantom limb goes away and the sensations are perceived differently.
One’s mental body image is quite robust. They can now hook up electrodes on the scalp to sample where these neurons fire in the brain and, with the aid of a computer, allow people who have lost their limbs, or the control of their limbs, to control artificial limbs with appreciable accuracy. It is also this mental body image that determines one’s threshold of pain through the mechanisms of distraction, expectation, desire, protest, etc. So, while all of this modeling takes place in the mind, the raw sensory material that is interpreted by the model does not.
I injured my elbow a couple of years ago. The pain was so intense I would have to take a couple hundred milligrams of morphine to manage it, and I would still wake up in the middle of the night howling in pain, and I would keep on howling until the meds I took kicked in up to a half hour later. One can only wonder what the neighbors thought.
Its better now, but sometimes I get so engrossed in something like Fluther that I don’t notice that my meds have worn off until I am really hurting. So, yes, there is some mitigation of pain depending on whether your attention is distracted. There is also some mitigation when the pain is considered normal and expected, as some women describe their menstrual cramps, and as I do now when my meds wear off. There is even greater mitigation when the pain is anticipated and desired, as some women report in respect to childbirth, or when you probe a sore tooth with your tongue.
On the other hand, even a slight sensation such as a sharp flick or a thwack with a finger can be perceived as highly annoying when it is persistent and unwanted. Torturers first show their victim the instruments of torture; then they tell them that no one will see how valiantly they resisted or bore up under the pain. The intent is to break down any resistance the person may have by undermining their anticipation and desire for pains that could be interpreted as a glorious martyrdom. From all accounts, it’s hard to predict who will break right away under torture and who will endure for a long time.
Whether a sensation is interpreted as pleasurable or painful is a judgement one makes based on whether the sensation is desired or not. For example, I experienced my first orgasm as painful because I wasn’t expecting it and it scared me, plus there were alarming quantities of all this “stuff.” I was sure I had broken something. A few days later curiosity got the best of me, and things turned out much more agreeably (and from then on, I was hooked). Same sensation, differently interpreted.
But, it is doubtful that I could interpret the pain in my elbow as anything but intolerable; so in this sense, the pain wasn’t “all in my mind.” On the other hand, there is a class of anesthetics, like ketamine and phencyclidine that induce a disassociative state, where you feel the pain but you don’t care because your conscious social self is so disassociated from your body self, it is as if the pain is happening to someone else. So, in this sense, pain is all in your mind.