Cats do smile, but not in the way that humans do – while we bare a grin to show our happiness, cats smile with their teeth, says Marci Koski, a feline behavior and training consultant. Cats smile by narrowing their eyes, shutting them partly or completely. Their pupils may also be dilated while doing this.
Humans by nature are more expressive, using the muscles in our faces to express happiness, disgust, anger, excitement and other emotions.
“Cats don’t have that range of facial expressions,” Koski says. “They evolved in an area or areas that were relatively resource-limited, so their territories were very large and close-up interactions between cats were fairly limited.”
Instead, cats use exaggerated body movements or expressions to show similar emotions. This could be hissing, growling, putting their ears back or to the side, puffing up their bodies or twitching their tails.
Smiling with their eyes is a more subtle expression, but it’s one they do with their humans and other cats alike. Two of Koski’s cats, who are mother and son, show this behavior – the son, Oliver, will only approach his mom to snuggle when she appears relaxed, with her eyes nearly closed.