Scientists have analysed brain activity to better understand why people experience 'cute aggression' -- the urge to squeeze a puppy or pinch a baby's cheeks. The study, published in the journal Frontiers in Behavioural Neuroscience, found that when people are overwhelmed by cuteness, the brain's reward system responds with aggression.Until now, research exploring how and why cute aggression occurs has been the domain of behavioral psychology, said Katherine Stavropoulos, an assistant professor at the University of California (UC) Riverside in the US.

However, Stavropoulos has taken formal study of the phenomenon a few steps further. In her research, Stavropoulos uses electrophysiology to evaluate surface-level electrical activity that arises from neurons firing in people's brains. Baby Lip Syncing to 'Girls Like You' With Dad is Too Cute to Handle, Watch Adorable Video.

By studying that activity, she gauges neural responses to a range of external stimuli. Stavropoulos wondered whether there was a neural component to cute aggression. She hypothesised that the brains of people who reported experiencing cute aggression would, in fact, provide evidence of detectable activity.

She suggested the activity might be related to the brain's reward system, which deals with motivation, feelings of "wanting," and pleasure, or to its emotion system, which handles emotional processing -- or, more likely, to both.

UC Riverside doctoral student Laura Alba recruited 54 study participants between the ages of 18 and 40, all of whom agreed to wear caps outfitted with electrodes. While wearing the caps, participants looked at four blocks of 32 photographs.

After viewing each block on a computer screen, participants were then shown a set of statements and asked to rate how much they agreed with them on a scale of 1 to 10. The survey was designed to assess how cute participants found each block of photographs -- known as "appraisal" -- and how much cute aggression they were experiencing in response.

Participants also rated how overwhelmed they felt after viewing the photos and whether they felt compelled to take care of what they had just viewed.They self-reported more significant feelings of cute aggression, being overwhelmed, appraisal, and caretaking toward cute baby animals than toward less cute adult animals.

Among the two categories of babies -- cute (enhanced) and less cute (non-enhanced) -- the researchers did not observe the same pattern. Using electrophysiology, Stavropoulos also measured study participants' brain activity before, during, and after viewing the sets of images.

Based on the neural activity she observed in participants who experienced cute aggression, Stavropoulos's findings offer direct evidence of both the brain's reward system and emotion system being involved in the phenomenon.

"There was an especially strong correlation between ratings of cute aggression experienced toward cute animals and the reward response in the brain toward cute animals," Stavropoulos said.

"This is an exciting finding, as it confirms our original hypothesis that the reward system is involved in people's experiences of cute aggression," she said."Essentially, for people who tend to experience the feeling of 'not being able to take how cute something is,' cute aggression happens," Stavropoulos said.

"Our study seems to underscore the idea that cute aggression is the brain's way of 'bringing us back down' by mediating our feelings of being overwhelmed," she said.