NOEL KING, HOST:
All right, the holiday season is winding down. This time of year often feels like it's all about the cute and the cuddly. Take a listen to this clip from Disney's "Lady And The Tramp" in which the wife, Darling, gets a big-eyed puppy on Christmas morning.
(SOUNDBITE OF FILM, "LADY AND THE TRAMP")
PEGGY LEE: (As Darling) Oh, how sweet.
LEE MILLAR: (As Jim Dear) You like her, Darling?
LEE: (As Darling) Oh, I love her.
KING: Now, here is something interesting. When some of us encounter too much cuteness, our brains generate ugly thoughts. NPR's Jon Hamilton explains.
JON HAMILTON, BYLINE: Scientists call it cute aggression. Katherine Stavropoulos is one of those scientists. She's a psychologist at the University of California, Riverside. And Stavropoulos says cute aggression is the reaction lots of people have when the adorable factor gets cranked up to 11.
KATHERINE STAVROPOULOS: It could be a cute animal or a cute baby. And they just have this flash of thinking, I want to crush it, or I want to squeeze it until it pops.
HAMILTON: Stavropoulos says those thoughts sound worse than they are.
STAVROPOULOS: When people feel this way, it's with no desire to cause harm. It's just that it's so cute they have this strange feeling. And most people feel like I - you know, I can't explain this. This is weird. I'm probably the only one who feels this way. I don't want to hurt it. I just want to eat it.
HAMILTON: Cute aggression was first described in 2015 by researchers at Yale. But Stavropoulos wanted to know what it looked like in the brain. So she and a colleague recorded the electrical activity in the brains of 54 young adults as they looked at images of animals and people. The images included both grown-ups and babies. And Stavropoulos says some of the images had been manipulated to look either less appealing or extra adorable.
STAVROPOULOS: So big cheeks, big eyes, small noses - all these features that we associate with cuteness.
HAMILTON: The study found that for the entire group of participants, cuter creatures were associated with greater activity in brain areas involved in emotion. But people who felt more cute aggression also had more activity in the brain's reward system. So Stavropoulos says people who think about squishing cute little puppies appear to be driven by two powerful forces in the brain.
STAVROPOULOS: It's not just reward, and it's not just emotion. It seems to be both. So both systems in the brain are involved in this kind of experience of cute aggression.
HAMILTON: The combination can be overwhelming, and scientists say that may be why the brain starts producing aggressive thoughts. The idea is that these negative emotions help people get control of the positive ones running amok. Oriana Aragon at Clemson University was part of the Yale team that gave cute aggression its name.
ORIANA ARAGON: It could possibly be that somehow these expressions help us to just sort of get it out and come down off that baby high a little faster.
HAMILTON: Aragon says about half the population experiences some level of cute aggression. And she says it's often accompanied by other contradictory expressions of emotion.
ARAGON: So people who, you know, want to pinch the baby's cheeks and growl at the baby are also the people who are more likely to maybe cry at the wedding or cry when the baby's born or more likely to also, you know, have nervous laughter.
HAMILTON: Aragon says she's one of these people.
ARAGON: For me, puppies are just amazing and adorable and cute. And I cannot resist them.
HAMILTON: She also says she's a sucker for cute movies. So I test her with the first cute puppy movie that comes to mind, "Lady And The Tramp."
ARAGON: Oh. That's a good one.
HAMILTON: Well, there you go, right (laughter)?
HAMILTON: Jon Hamilton, NPR News.
ARAGON: Too cute, way too cute.
(SOUNDBITE OF SONG, "BELLA NOTTE")
UNIDENTIFIED SINGERS: (Singing) This is the night. It's a beautiful night. And we call it...