Maybe her new roommate can help.

Karen was unsurprised to find her coworker Melissa lounging on her couch when she arrived home.

"Hey!" Melissa said. "Welcome home."

"Thanks," she grumbled. She didn't even know Melissa had her address. They weren't particularly close; Melissa was an introvert and visibly awkward and nervous in the company of others.

"Hey, come in here!" Melissa said, hopping up from the couch. "I wanna do something."

Karen shut her door with a sigh before letting Melissa lead her into the kitchen. She raised her arms with a sigh before putting them back down. Melissa was rummaging in the fridge now.

"What are you going to do?" Karen asked. All this beating around the bush was just the price of talking to Melissa. She shivered briefly from the cold.

Melissa wiped her mouth and smiled innocently. "I'm already doing it."

"You're not doing anything different from what you always do."

Melissa grabbed a paper towel to wipe off her face and straightened up. Karen rolled her eyes at the smug grin on her coworker's face.

"Here, hop up on the counter," Melissa directed. Karen did as instructed, wondering when Melissa was going to leave. She giggled involuntarily.

"Something funny?" Melissa asked. Her face was covered in white foam.

"That tickles! And yes, you look ridiculous! Not exactly out of character for- ahaha, quit it!"

"What if I told you I'm acting out of character right now?" Melissa's hands felt good on her bare back, a warm buffer against the tile backsplash.

"But you're not," Karen objected.

"Let's try something," Melissa said. "Why don't you start listing things I'm currently doing and see if any of them feel out of place?"

Karen shrugged. "Ok, I guess. You're breathing, you're talking to me, you're eating... oh, is it weird to eat in front of me? It seems perfectly normal for you to eat where I can see."

"Mm-mm," Melissa said. She shook her head, smearing cream everywhere and tickling Karen again, then raised it to speak. "You're on the right track."

"Is it what you're eating?" Karen asked. "I mean, I really can't see what's weird about eating whipped cream but I guess that's the point. Guess which perfectly ordinary thing seems weird to you? This could go on forever! We'll run out whipped cream, and I doubt you want to lick barbecue sauce off my tits."

Melissa snort-laughed, spraying whipped cream everywhere, and Karen had an insight. "It's something about that, right? It's weird that you're licking my tits?"

"Bingo!" Melissa said to her left nipple.

"So you're saying if you want to feel them, you can only use your hands? And is all licking banned, or just boobs? This doesn't make any sense." Karen shivered as Melissa sucked her right nipple between her teeth.

"Here's a thought experiment," Melissa said after spitting out a stray hair. "What if everyone's ability to tell what's normal was broken?"

"But everyone-"

"It's just a thought experiment," Melissa interrupted. Poor, shy Melissa, just as cringing and nervous as ever. "Picture this: a person loses all ability to detect abnormalities. Not you, a fictional person. Let's call him Tom. Tom can't tell usual from unusual - seeing his neighbor pissing in his mailbox is no more noteworthy than seeing him mowing his lawn."

"Ok," Karen muttered. The faster she indulged this the sooner Melissa would go home. It did remind her of how people were being aggressively normal no matter how weird she was...

"Oh, shit!" Karen said. "Everybody else can't tell what's normal! That's why they're acting so nonchalant about everything. Doesn't that mean you can't tell if I do something weird?"

Melissa was now roughly groping her right breast. "For all I know, you could have been acting weird since you walked in. Oh, and I'm gonna live with you rent-free. We can share a bed."

"Are you serious?" Karen grunted, bracing herself against the motorboating she was receiving. "You couldn't tell if I was doing anything strange? Shit, I just remembered I lost my spare key. We'll have to go get mine cloned for you."

"Thanks. And I'm telling you, as far as I can tell you're behaving exactly as you always have." Melissa asked.

"You seriously don't see anything weird about my behavior?" Karen asked. "Think about it. You groped me for twenty minutes. Melissa, I'm not even into girls!"

"Does that mean you didn't like it?" Melissa asked, a sly smile creeping across her features

"Not necessarily."

"Good to hear," Melissa said, and pinched Karen's left nipple between her teeth. Karen yelped. "Next question: could someone who lost the ability to perceive deviations even learn that they have the condition?"

"...I guess not," Karen said thoughtfully. "Because the condition is abnormal. I guess you'd have to approach it in a more abstract- ow!"

Melissa grinned up at her and finished her thought. "...way, like setting up a hypothetical. But even then there's a certain intuitive leap that she would have to make. She'd have to, without prompting, recognize the parallels between the hypothetical and her experience, and even then-"

Karen cut her off by shoving Melissa's face into her breasts. She laughed, partially from the motorboating and partially because she now had a foolproof way to cut off another monologue about thought experiments from her shy, quiet roommate.