Why You Should Blink at Your Cat

The Duchenne smile, with its charming crescent-moon-shaped eyes, touches the soul. It is universal, spanning across cultures and even species, albeit in different forms. Narrowing the eyes has been found to indicate positive emotions across species including dogs, horses, and cows. But while it is commonly said that cats narrow their eyes or blink to show love and trust, research had yet to test this empirically. Thus, Humphrey et al. (2020) conducted a study to test how cats react when humans blink at them.

In Study 1, the researchers recruited 18 indoor/outdoor cats from 14 different owners to observe their reactions to their owners’ blinks. The study was performed at home for the comfort of the cats. The researchers trained owners to perform the slow blink sequence, “a series of half-blinks followed by either a prolonged eye narrow or an eye closure." The eye closure at the end had to be at least 0.5 seconds long. In the control condition, the owners were in the same room as their cats but did not interact with them. Responses of the cats were coded through the CatFACs, "an anatomically based system designed to objectively measure facial actions based on their underlying muscle movements." Results indicated that cats slow blinked more when their owners slow blinked at them versus when they did not interact with them.

In Study 2, the researchers sought to understand whether cats’ responses generalized to strangers (i.e., the experimenters), and whether slow blinking would attract cats to them. Study 2 included 18 new cats from 8 different owners and again took place in the cats' homes. To draw out approach behaviors, experimenters sat or crouched down and held out a hand to the cat. They either performed the slow blink sequence or showed a neutral expression with no eye contact. Findings were that, again, cats were more likely to blink at strangers who blinked at them versus strangers who showed no expression or eye contact. In addition, in this condition, cats were also more likely to approach strangers. Overall, cats showed approximately 5% more approach responses in the blinking condition as opposed to the neutral condition.

In summary, despite the many anecdotes about kitty blinks, this study was the first to empirically demonstrate that 1) blinking is a positive form of communication for cats; and 2) blinking can make a cat approach a stranger.

However, there is still much more to learn about that cat’s blink, or their “Duchenne smile." First, we don’t know the exact emotions associated with their blinks—is it really love?—or the exact purpose of their blinks. While laypeople claim that kitty blinks show love and trust, Humphrey et al. (2020) posit that the blinks may have a more practical origin—specifically, that they may serve as a way to interrupt a stare, which is often threatening to cats. In relation, we still don’t know the actual origin of the blink. The researchers suggest that future studies examine whether blinks are an evolved or learned behavior among cats.

Humphrey et al. (2020) also point out the implications of the cat blink. Given their positive nature, kitty blinks can be used to evaluate how well cats are doing in different settings, including with veterinarians, in shelters, and in foster homes; and importantly, to enhance relationships between cats and humans.