Raj gets asked about his love life and he admits that he broke up with his girlfriend because she didn’t want to see him anymore. Sheldon insults Raj by comparing him to a virgin Isaac Newton. Then Raj really starts to wonder why women don’t really like him. Amy brings up the fact that a group at M.I.T. has developed a detector that correctly reads human emotional levels 85% of the time. Sheldon decides to borrow one to help test it and help him with human interaction though he wants to use it to determine the fears of his enemies so he can destroy them.
The two apartment couples are discussing what to do with Sheldon’s old room. Sheldon suggests a train room; an idea which no one else likes. Also, M.I.T. is sending Sheldon a prototype emotion detector to do a beta test. Raj wants to use it to understand why women keep dumping him. Howard suggests that he just send out a survey to them. Raj decides to invite them all over as a focus group which everyone else thinks is a bad idea. Also Penny announces that she invited her brother out to help him find a job at her dad’s request without telling Leonard. Leonard is not happy and thinks that he’ll just have a new market to sell his drugs in. Sheldon shows up with his emotion detector that reads human reactions and display the results on his phone. It can only detect happy, sad, angry and excited. Raj tells everyone that he is going to have his ex-girlfriend focus group at his apartment to help improve himself. The rest think he is just going to get emotionally hurt. Sheldon uses the detector on Leonard explaining that he is angry about his brother-in-law staying with them which starts a fight with Penny.At Raj’s apartment, he is meeting with deaf Emily, Lucy, Emily and Claire with Howard interpreting for the first Emily. Lucy broke up with him because he forced her into uncomfortable situations like this one. Raj agrees that he can be insensitive about other people’s boundaries. Claire broke up with him because she found him extremely needy and vain. Only one comment per girlfriend. Emily is not comfortable with sharing details about their relationship in front of Howard. She had problems with him in bed. Raj told Howard to leave, though he didn’t. Amy has made dinner and calls it beef loaf because Sheldon is unhappy with the non-specificity of meat loaf. Sheldon is not happy with the device. He has always had problems recognizing people’s emotions, but the device made it so much more real. Sheldon admits that Amy is something of a sad sack, but he loves her just the way she is..
Deaf Emily being interrupted by Howard says that she thought Raj was great, but he was so dominated by his parents. Emily called him a “mama’s boy”; however Raj wrote down “loving son”. Also, all the women found someone new and better and they learned from Raj what they didn’t want in a man. Deaf Emily traded him on for a "Bruce Wayne", another rich guy. They also pointed out that it is great that he is willing to improve himself.
Sheldon returns to apartment 4A and is sorry that he started a fight between the Hofstadters. Penny has decided to tell her dad that it’s not a good time for her brother to visit.
Raj thanks the women, but considers it a waste of time since he just ended up beating himself up. Howard says that that is his job. Howard suggests that if he breaks up with Bernadette that in thirty years the two of them can try to get together. They could attend all the gay pride parades together.
- Guest starring:
- Teleplay: Steven Molaro, Steve Holland & Saladin K. Patterson
- Story: Chuck Lorre, Dave Goetsch & Anthony Del Broccolo
- Title Reference: Sheldon uses a machine to detect people's emotional levels.
- Taping date: January 10, 2017
- This episode was watched by 14.66 million people with a rating of 3.1 (adults 18-49).
- Total viewers including DVR users 19.32 million.
- The Big Bang Theory was ranked #3 for the week ending on February 5, 2017.
- This episode aired in Canada on February 2, 2017.
- Caroline Preece at Den of Geek! - Even by its own standards for strangeness, The Emotion Detection was a very weird episode of The Big Bang Theory. In a lot of ways it was business as usual, with Penny and Leonard (and even, for a while there, Raj) having their stories invaded by Sheldon, and in others it felt like a recalibration of some of the ways the show has been dealing with certain storylines this season and beyond...The first thing we hear is that Raj’s girlfriend who we met once and seemed to be popular with audiences (and an immigrant with an entirely different story to Raj’s, which would be very welcome in 2017) has broken up with him. He doesn’t know why,...Enter the gathering of ex-girlfriends, which was entertaining to me if only because it reminded me that Switched at Birth’s Katie Leclerc was once on this show. This kind of storyline is a trope of sitcoms that usually comes about through some hijinks, but here it’s simply Raj summoning the women of his past to tell him why they dumped him. 
- IMDb user reviews
- Leonard's behaviour during his fight with Penny about Randall getting a job in Pasadena and moving there completely contradicts his friendly, sweet, kind and reasonable personality.
- Emily, Lucy, Claire and deaf Emily all return to talk to Raj at his request. They reappear since these episodes:
- Randall is mentioned in this episode, but does not appear.
- Howard shouldn't be signing for Raj since he learned while he was dating the first Emily.
- Raj just doesn't know this, but he is not alone. There were a few pathetic guys who were bad as Raj is in relationships: Stuart Bloom, Barry Kripke, Leonard Hofstadter, Bert Kibbler, Dr. Oliver Lorvis and Howard Wolowitz. Even Sheldon Cooper himself was terrible with relationships, though this was by choice.
- All of Raj's ex-girlfriends are now in happier relationships.
- Howard and Raj have frequently been mistaken for a gay couple in the past. In this episode, they decide to give a homosexual relationship a try in the future if things don't work out for them right now, as Stuart "dibs-ed" Bernadette.
- Third consecutive episode where Leonard and Penny fight.
- As of this episode and season, Laura Spencer is no longer billed in the opening credits.
- Theodore no longer lives in Apartment 4A anymore since Sheldon's old room was becoming a game room and Randall would be coming and in "The Escape Hatch Identification" (S10E18), Theodore's departure is once again confirmed when Raj moves into Apartment 4A into Sheldon's old room.
- For the first time ever, Amy mentions her father, but unfortunately no information about him is given out.
- Raj found out why his relationships never last: He is too needy, too pushy, a Momma's boy, he reeks of desperation and sometimes he could very arrogant sometimes.
- Howard (to Raj): Is that any way to talk to your future husband?[first lines]
- Penny: Hey, boys, .how's it going?
- Sheldon: I thought we were having a nice conversation. but it turns out I was being offensive
- Bernadette: So, normal, hm?
- Sheldon: Well, I would prefer if people told me exactly what is on their mind.
- Penny: No, no, you don't; you really don't. I can't actually say don't enough.
- Bernadette: You know, I just read that a team at MIT developed a device that helps people read human emotions.
- Leonard: And you think we can get those guys to reprogram Sheldon? Cool.
- Bernadette: It's supposed to be accurate like eighty-five percent of the time.
- Penny: Wow, I find that hard to believe.
- Leonard: That a bunch of awkward scientists with no social skills would invent a machine to do it for them?
- Penny Hofstadter: I take it back; I believe it.
- Penny: So, did you wind up sending that machine back?
- Sheldon: I did .Uh, I'm not even sure how accurate it was. I took it to the trains store; it said everyone was sad.
- Bernadette: I finally got Halley to sleep.
- Penny: You know, I just read a study that suggests new mothers are better at sensing emotions for up to two years.
- Amy: It's true. Pregnancy causes physiological changes in the brain that result in increased empathy.
- Penny: Oh, so all we need to do is get Sheldon knocked up.
- Leonard: Can't. He was already fixed when I found him at the shelter.
- Sheldon: Hey, uh, Bernadette, let's test this theory. What do you think I'm feeling right now?
- Bernadette: Let's .see. You're better than us, a little bit sorry for us, but mostly glad you don't have to be us.
- Sheldon: [to Howard] Keep filling this one with babies; she's good.