You are sitting on the sofa and your cat is across the room, gazing at you. Slowly, almost lazily, its eyes narrow to soft slits and then drift half-closed before opening again. It is one of the gentlest expressions a cat ever makes, and cat lovers have long called it the "slow blink" or the "cat kiss." For years it was treated as charming folklore — a sweet thing cats supposedly did when they were content. Then, in 2020, scientists actually put the idea to the test. The result was one of the first experimental studies to show that this little eye movement is a genuine form of communication between cats and the people they live with. Here is what the research found, what the slow blink really means, and how to blink back.

What a Slow Blink Actually Is

A slow blink is not the quick, reflexive blink a cat does to keep its eyes moist. It is a deliberate, drawn-out sequence: typically a series of half-blinks where the eyelids partly lower, followed by a prolonged narrowing of the eyes or a soft, sustained closure. The whole gesture unfolds over a second or two rather than a fraction of a second. The eyes look relaxed and slightly almond-shaped, the face is loose, and there is none of the tension you see in a frightened or defensive cat. Behaviorists sometimes describe the resulting expression as the feline equivalent of a smile — a signal of ease rather than alertness.

The 2020 Study That Changed the Picture

The key evidence comes from a study led by Dr. Tasmin Humphrey and Professor Karen McComb of the University of Sussex, published in the journal Scientific Reports in October 2020 under the title "The role of cat eye narrowing movements in cat–human communication." The researchers ran two carefully controlled experiments to find out whether slow blinking really works as a social signal.

In the first experiment, owners slow-blinked at their own cats from across the room, and the cats were significantly more likely to slow-blink back than when the owner was present but not blinking at them. In the second experiment, an unfamiliar researcher — someone the cat had never met — either slow-blinked at the cat or held a neutral, non-blinking expression. The cats not only returned the slow blink more often after the human slow-blinked, they were also more likely to approach the stranger's outstretched hand afterward. In other words, a slow blink from a person made cats more willing to come closer, even to a total stranger.

So What Does It Mean?

The Sussex team concluded that slow blink sequences function as a form of positive emotional communication between cats and humans — something close to the feline version of a friendly gesture. When your cat slow-blinks at you, the most likely interpretation is that it feels safe, relaxed, and content in your presence. Crucially, the study showed the exchange runs in both directions: cats respond to a human slow blink with one of their own, which is why so many owners report that blinking at their cat "works."

There are a couple of leading explanations for why the gesture carries this meaning. One is simply that narrowed, half-closed eyes are physically incompatible with aggression or fear — a tense, threatened cat opens its eyes wide and stares hard, so soft eyes broadcast the opposite message. Another is that, because cats often find a direct, unblinking stare confrontational, breaking that stare with a slow blink may serve as a deliberate signal of non-hostility, reassuring the other party that no threat is intended.

More Than Just a Sweet Habit

The slow blink may have practical value too. A separate 2020 study published in the open-access journal of the same family looked at shelter cats and found that cats who closed their eyes slowly in response to a human slow blink — and those who showed more eye-closure behavior overall — tended to be adopted more quickly than cats who did not. That suggests the gesture is not only a sign of a relaxed cat but also something humans intuitively read as friendliness and are drawn to. For cats living in stressful shelter environments, being able to send and receive this signal may genuinely improve their chances of finding a home.

How to Slow Blink at Your Cat

The lovely thing about the research is that it gives you something to do with it. You can try the technique yourself, and many cats will answer:

If your cat does not blink back, that is perfectly normal — mood, distractions, and individual personality all play a role, and a cat that simply looks away calmly is also signaling that it feels at ease.

When Eye Behavior Is Worth a Closer Look

A relaxed slow blink is a good sign, but not every change in a cat's eyes is about affection. Persistent squinting in one eye, excessive blinking, watery or crusty discharge, redness, pawing at the face, or a visible third eyelid can point to eye pain, infection, injury, or other medical problems and are quite different from a calm, two-eyed slow blink delivered from a comfortable distance. If your cat is squinting frequently, holding an eye partly shut on its own, or showing any discharge, treat that as a reason to check in with your veterinarian rather than a love message. The affectionate slow blink, by contrast, is symmetrical, unforced, and comes from a cat whose whole body looks loose and content.

The slow blink is one of the rare cases where a long-standing piece of cat-lover folklore turned out to be backed by real science. Your cat narrowing its eyes at you across the room is, in all likelihood, a small signal of trust — and one you can return.