Children as young as three recognise "cute" features that encourage care-giving in adults, a study has found.
Even before they start school, children rate puppies, kittens and babies as "cuter" than their adult counterparts.
Cuteness is wrapped up in what psychologists call "baby schema" - a set of infantile features such as a round face, high forehead, big eyes and a small nose and mouth.
Baby schema has been shown to stimulate protective, care-giving behaviour and reduced aggression in adults.
Marta Borgi, from the University of Lincoln, who led the new research, said: "We already knew that adults experience this baby schema effect, finding babies with more infantile features cuter.
"Our results provide the first rigorous demonstration that a visual preference for these traits emerges very early during development.
"Independently of the species viewed, children in our study spent more time looking at images with a higher degree of these baby-like features."
The researchers conducted two experiments with children aged three to six. One tracked eye movements to see which facial areas children were drawn to and the other assessed how cute children rated animals and humans with infantile traits.
Images of human adults and babies, dogs, puppies, cats and kittens were digitally manipulated to make them appear "cuter".
The same photos were also made less cute by giving subjects more adult-like features, such as a narrow face, low forehead and small eyes.
"Interestingly, while participants gave different cuteness scores to dogs, cats and humans, they all found the images of adult dog faces cuter than both adult cats and human faces," said Ms Borgi.
Professor Kerstin Meints, from the University of Lincoln's School of Psychology, who supervised the research, said: "We have also demonstrated that children are highly attracted to dogs and puppies, and we now need to find out if that attractiveness may override children's ability to recognise stress signalling in dogs.
"This study will also lead to further research with an impact on real life, namely whether the 'cuteness' of an animal in rescue centres makes them more or less likely to be adopted."
The findings appear in the journal Frontiers In Psychology.