Written by Emily Nagoski, Ph.D.
What I mean is, you know how when someone tickles you and you're feeling all playful and fun and it's enjoyable? And then there's other times when you might be annoyed or bored and someone tickles you and it just pisses you off? Same sensation, different context, therefore different experience. Sensation is contextual.
It's true of pain, as well as tickling.
See, experienced sensation can be described with two different vortexes: intensity and valence. Intensity is the scale of the experience and valence is the direction (good or bad) of the experience. Both are relative and contextual.
Paper cuts hurt, but not as much as a paper cut plus lemon juice, which itself is not as bad as banging your thumb with a hammer, which is not as bad as breaking your leg, which is not as bad as childbirth. That's intensity.
In an ordinary context, a spanking is a slap and a sting. It hurts. But say you're all turned on and good sexy things are being done to you by a partner you like and trust, and then they slap you on the ass. In an erotic context, it's still a slap and a sting, but your brain, primed for erotic sensation, interprets it as erotic.
Let's see if I can remember my neuro-anatomy: there are two basic streams for sensations, one that responds to light touch and one that does deep touch, aka pressure. Tickling is light touch. Slapping is deep touch, as is massage. Stroking is light, squeezing is deep. Note well: sensations are not divided up by "pleasurable" and "painful," but by light and deep. Pleasure and pain are your brain's interpretation of sensation, they are not characteristics of the sensations themselves.
As someone recently said when she learned this, "That makes sadomasochism seem less freaky." Yes indeed. It's just an erotic context for what isn't ordinarily sexy.