The cute aggression response – the urge some people experience to squeeze, bite, or crush when they're presented with a cute baby or animal – has been measured for the first time in the brain.
The research, published in the journal Frontiers in Behavioural Neuroscience, involved 54 participants undergoing electroencephalogram (EEG) testing — a non-invasive technique for measuring brain activity using what are essentially swimming caps with electrodes sewn into the lining.
Wearing the EEG caps, the participants were exposed to four different sets of images: babies that were edited to look cute (with features such as bigger cheeks and larger eyes); babies that were edited to look less cute (with smaller eyes); baby animals' and fully grown animals.
The participants were then asked to report their feelings looking at the images and asked if they felt a sense of being overwhelmed, an increased need for caretaking, and the amount of cute aggression they were experiencing.
Using those answers, the researchers measured the participants' brain activity in the emotion and reward systems of the brain and were able to map the pathways of cute aggression.
The researchers found that amongst people who experiencing a strong sense of cute aggression, the response was being caused by two strong emotions: a caretaking response and a sense of being overwhelmed by positive feelings.
The people who experienced a strong feeling of cute aggression also showed increased activity in the reward centres of their brains, which is the first time these centres have been implicated in the response.
Lead author of the study, assistant professor Katherine Stavropoulos from the University of California, Riverside, told BuzzFeed News that the results show how cute aggression is an example of the brain trying to "re-balance" itself when a person is feeling overcome by emotion.
The brain shows the same attempt to regain emotional equilibrium when people do things such as begin to laugh while crying, or vice versa.
"I think that cute aggression likely serves as a way to counteract our feelings of being overwhelmed by something cute," she said. "Essentially, if we were too overwhelmed by how cute something was to take care of it, that doesn't work evolutionarily."
The study also highlights the need for researchers to understand why some people experience cute aggression while others don't.
"We know it has a lot to do with whether someone is overwhelmed by their strong feelings, but still do not fully understand why some people are overwhelmed," said Stavropoulos.
Cute aggression was first investigated by researchers from Yale University in a study in 2015, which found that adults reliably reported feelings of cute aggression towards babies that were digitally manipulated to look cuter, as compared to babies that were manipulated to look less cute.
While the response is common, cute aggression doesn't seem to be universal.
Among the participants in Stavropoulos' experiment, 64% reported having ever said a statement such as "It's so cute I want to squeeze it!" and 74% said they had previously squeezed a cute animal.