Work Header

Psychophysical Examinations of Perceptual Effects of Differential Somatic Stimulation (or: Fuck Off And Leave My Bloody Balls Alone, Would You, Sherlock?)

Work Text:


Previous research on the sexual response patterns of subject JW has been fragmentary and extremely poorly documented. The present study aims to rectify this oversight with a comprehensive somatosensory mapping endeavor. A strong positive correlation was found between response intensity and seconds since commencement of the trial (r=0.74), implying sensitization as opposed to habituation while in an aroused state...


Sherlock doesn't usually ask permission before setting off on his madcap expeditions into the world of scientific discovery, so when he takes the time to explain the details of his current hypothesis, John is too busy being grateful for the warning to pay attention to what he's actually saying.

"...the effectiveness of various haptic stimuli on the somatosensory component of hedonic response," concludes Sherlock. "All right?"

"All right," says John, because it's usually easier not to ask for clarification when it comes to Sherlock's home-cooked science projects.

Sherlock waits expectantly.

"What?" says John.

"Take them off, then," says Sherlock impatiently. He glares at John's trousers like they've just said something rude about his mother.

"Wait," says John. "Go over that again, the part about somatosensory stimulation?" He's not a neural specialist, but they don't let you graduate med school without learning a thing or two about the parietal lobe, and he's not at all sure he wants Sherlock using him as a subject for tactile sensation experiments. Particularly if they involve the removal of his trousers.

"My applied research in the area of targeted haptic stimulation requires significant further investigation before my expertise reaches an acceptable level. I need to perform additional trials. You said all right," he adds reasonably.

John pauses for a moment to decode. "You want to be a better lay," he translates slowly, "and you're asking if you can fuck me for practice."

"For the third time, yes," says Sherlock.

John breathes a sigh of relief. He was worried he'd just signed up for torture sessions. "Right," he says, and begins to strip.


If the point of the thing is to improve Sherlock's skills in bed, John is of the opinion that there should be a bed involved. Or a sofa, shower, or kitchen table. John's had sex standing up, but not without any kind of vertical surface involved for leverage, and he has his doubts about whether Sherlock's muscular endurance is up to the challenge.

"We're not having sex yet," says Sherlock. "The standing is to minimise sensory noise. Mark F3."

"You're stimulating my cock," says John. "I think it's at least borderline sex."

"Shut up and mark the LMS sheet before you invalidate my data. You're getting too erect."

"Never had that complaint before," mutters John, but he obediently marks the line labeled F3.

Sherlock pokes the back of John's knee. "F4."

"That tickles," says John, trying not to wriggle as he marks the sheet and flips the page. He hopes the knee is a control or something, and Sherlock isn't planning on fucking it. He doesn't really want to think about how that would work. Not that he would put it past Sherlock to come up with a way to shag someone's knee.

He's never had sex holding a clipboard before, either. He looks down at the series of labelled lines on the paper. "I have to say, this measure seems a bit woolly," he says.

"Studying sensation at all is woolly," says Sherlock. "The LMS is fine for a within-subject design. G1." He sticks his finger up behind John's balls.

"Oi!" says John. "Can't you warn me when you're headed to the dark places?"

"Certainly not," Sherlock says, his expression innocently neutral. "That would compromise the science. G1, mark it."


John moves the little plastic slider back and forth, watching the line on the laptop screen go up and down. He's not sure he's going to be able to focus on keeping it accurate while he's getting a blowjob. Oh well. At least he gets to sit down for this bit.

He looks down to where Sherlock is resting a piece of paper against his stomach. "Give me a paper cut on my dick and I will drop out of this study immediately," John warns.

"Don't look at this," says Sherlock, hiding the paper with his hand. "Don't look at the screen during the trial, either. And remember that you're not reacting to intensity, you're reacting to pleasure." He props a stopwatch on the arm of the sofa. John averts his eyes from the screen and positions the slider in the middle.

All at once, Sherlock hits a key on the laptop with one hand, presses a button on the stopwatch with the other, and drops his mouth down onto John's cock. John shifts the slider a bit to the right, then a bit more when Sherlock seals his lips around John's cock and sucks.

Then Sherlock bites him.

"Ow ow, what the fuck!" John squawks, and hammers the slider against the left edge of its track. "What was that for?"

Sherlock mumbles something about calibration and goes back to sucking. John reluctantly moves the slider back to the middle. "You do that one more time and I'm not letting you anywhere near my genitals ever again," he says.

Sherlock mumbles something else.

"Bloody right," says John. "I'll impede your scientific process like a crazed ferret in a centrifuge, I--oh fuck, yes, that thing you just did, with the tongue..." He fumbles for the slider.


"A4," says Sherlock, touching John's nipple.

"I agree, the sheet does appear to be A4," says John as he marks it.

Sherlock's finger moves to the head of John's dick, right at the tip. "B1."

"Bollocks, you've sunk my battleship."


That's the crease of John's thigh, which is surprisingly sensitive. He marks it higher than most of the rest as he says, "That reminds me, I ought to take my multivitamin."

"B3." Sherlock touches his inner wrist.


Sherlock frowns at him.

"What?" says John. "As long as I'm a smartarse the whole way through, it's fine for a within-subject design, isn't it?"

"C1," says Sherlock, and touches the underside of John's dick.

John sighs and marks the paper. "Can we go back to the blowjobs soon? I was quite enjoying that. Apart from the teeth."


Sherlock is giving John a look that falls somewhere between a pout and a glare. John remains unmoved. He may be willing to indulge his insane flatmate to unreasonable extents, but he does have limits.

"You are not sticking a ruler up my arse and that's final."

The pout-glare shifts further toward the pout, like Sherlock's expression has a little plastic slider of its own. John shakes his head and keeps his bum planted firmly and inaccessibly on his bed.

"Why not?"

"It would hurt."

"If I gave a toss about human suffering, I'd've run my methods past an institutional review board," grumbles Sherlock. "We all have to make sacrifices for knowledge, John."

John folds his arms. Sherlock sighs in a persecuted sort of way. "All right then, I won't do it."

He's still holding the ruler. John doesn't move.

"I'll use my finger and then measure the finger," says Sherlock impatiently. "Much less exact, but I suppose it'll have to do. Turn over."

John has heard that some research participants get rewarded for their time and effort. Some scientists pay their subjects actual money. That sounds rather nice. Better than verbal abuse and anal violation, at any rate.

The anal violation doesn't go all that badly, actually. Sherlock uses enough lube and doesn't try for more than one finger, and it's not like John hasn't done this before. It's pretty much exactly like a prostate exam, the way Sherlock feels around for the gland and prods it from a few angles when he finds it.

The finger withdraws, and Sherlock says, "Three point four centimetres from the anus."

A thought strikes John. "Why are you bothering to measure?" he asks. "You can find statistics about things like that online."

Sherlock doesn't answer. Instead, he inserts his finger again and commences prodding. John buries his face in the duvet and waits it out.


"No, really," says John. "Why did you take that measurement?"

Sherlock regards him as if he's stupid.

John bristles. "And another thing," he says, irritated. "Why are you quantifying all this data from just one person? You can't run statistical analyses on a sample of one, and you're never getting anyone else to--"

Then he works it out.

He stops short, then shakes his head. "Bloody hell, Sherlock," he says. "Only you. You are the only person in the universe sneaky enough to shag someone for a week and a half without ever letting on that you actually want to shag them."

Sherlock smirks. "Maybe you're just the only person in the universe oblivious enough to be shagged for a week and a half without noticing."


Sherlock lays off the experimentation for a couple of days. He spends a lot of time on the computer, presumably analysing his data. John enjoys the reprieve from molestation. The blowjobs were all right, if oddly structured, but the rest of it wasn't all that much fun. Just goes to show that science can't solve everything.

Then Sherlock ambushes him from behind as he's making his bed one morning. One moment John is matching up the corners of his pillowcase to the corners of the pillow inside it, and the next there are slim arms snaking around his waist, deftly slipping off his bathrobe and teasing shivers out of his nipples and hips.

John's never had someone so much taller than him before, and the benefits are clear when Sherlock bends his head forward to tongue that one spot just above John's collarbone. John tilts his head to give Sherlock better access, and feels Sherlock's hands roaming slowly down his stomach. John is hard already, and gets harder when Sherlock runs a gentle finger down the crease of his thigh. Surprisingly sensitive, John remembers. He pushes forward into the touch, wanting more, and Sherlock obligingly begins stroking his cock.

This is familiar too, the way Sherlock is focussing his touches on the bits of John's cock that he marked the highest on the sheets. John is beginning to suspect that Sherlock may have actually had some idea of what he was doing with those.

The hand that isn't on John's cock moves around behind him. There's the sound of a click and then lubed fingers probing at John's hole. John is really going to have to find out what kind of tube Sherlock's lube comes in, because he's never managed to do that one-handed in his life.

Sherlock's grip on John's cock tightens a bit just as the second finger slips in, and suddenly there are two fingertips pressing on just the right spot to make John moan embarrassingly loudly. Sherlock kisses up John's neck to suck briefly on his earlobe, then he's going down on his knees. John panics for a moment about whether he's showered recently enough for that to be a good idea, but Sherlock ducks down past his arse and starts licking the back of his knee instead.

John has just enough time to think What the... before he comes all over his neatly made bed.

"It's shocking," Sherlock says, sounding far too smug, "that in today's day and age, there are still people who doubt the scientific method. Dreadful, really."


The first time John goes down on Sherlock, he uses his teeth, just to be a bastard.

Sherlock draws in a long breath that doesn't sound much like pain and says, "Do it again."

John raises his eyebrows at Sherlock's belly button. Perhaps he ought to conduct a little research of his own.