It's no secret that pain is often pleasurable here. The whole principle of BDSM is that the line between pain and pleasure is fine - so fine, in fact, that pain can enhance pleasure. While yes, a good deal of that is the neurotransmitter cocktail the right dose of pain doles out, a lot of it has to do with human perception.
Take this TED Talk from psychologist Paul Bloom, where he discusses the origins of pleasure and why, exactly, we are so attached to certain objects, sounds, and sensations.
"We don't just respond to things as we see them, or feel them, or hear them," he says. "Rather, our response is conditioned on our beliefs, about what they really are, what they came from, what they're made of, what their hidden nature is."
This phenomenon is called essentialism - meaning that how we experience something, anything, is determined in its essence. He uses paintings done by famous artists as an example. Would you prefer a Picasso original to a forgery? Of course! Some of why you enjoy that piece of art is how it looks, but a larger part is the piece of history it carries.
Another example is music. Would you still like your favorite guitar player's music if you had no idea they were the one playing? Maybe, but maybe not. This can be applied to almost anything: food, travel, smells, and yes, sexual acts. Interesting enough, this theory doesn't just hold up with pleasure - it's also true of pain. If you think someone hurt you on purpose, for example, it will actually hurt worse than if you think it was an accident. Here's what Paul Bloom said on the matter:
"The most extreme example of this is that in some cases, pain under the right circumstances can transform into pleasure. Humans have this extraordinarily interesting property that will often seek out low-level doses of pain in controlled circumstances and take pleasure from it - as in the eating of hot chili peppers and roller coaster rides. The point was nicely summarized by the poet John Milton who wrote, 'The mind is its own place, and in itself can make a heaven of hell, a hell of heaven.'"
When you consider that your feelings about certain kinds of pain, pleasure, and fetishes matter more than the objective qualities of those things themselves, sex itself starts to make a lot more sense. If your perception of being tied up by a trusted partner is positive, you're a lot more likely to not only participate but to thoroughly enjoy it. Masochism and sadism take on a bit of a newer shine.
Growing up, my mom always said that life was 99 percent about your attitude - and as more and more research about psychology and neurology comes out, it seems to me that she might have been quite literally right, especially when it comes to the sexual stigmas we each carry. Not every kink or person is for everyone, of course, but perhaps we have more control over what we like and don't like than we think.