Why do cats slow-blink?

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29 June 2021
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Dr Lauren Finka explores the latest research into the role of ‘slow blinking’ in cat-human interactions.

Many cat aficionados out there will already be familiar with the special type of ‘slow blink’ that cats often seem to perform in the presence of humans. It is commonly thought that when cats blink in this way they are in effect smiling with their eyes; the slow blink being an indication they are feeling relaxed and happy in our company. Many cat owners might also be regular slow blinkers at their cats (perhaps without even realising). Indeed, when we perform this behaviour towards cats, they can often respond positively (for example, approaching us for interaction).

However, those of us who study cat behaviour for a living, may have also noticed cats sometimes performing these sorts of blinks when the rest of their body language and behaviour would suggest they are uncomfortable.

For example, I have seen many cats slow blink when they are also displaying a range of subtle indicators of discomfort or conflict, such as a tense posture that is angled or leaning away from the person they are blinking at (suggesting they want to avoid contact).

In these situations, the cat might also have a tense facial expression, more rounded than almond shaped eyes, and ears that rotate or flatten slightly. These cats might also tend to perform other conflict-linked behaviours, such as licking their nose, sudden rapid self-grooming, and shaking of their head, or turning it to one side. What these different observations may suggest is that the slow blink may mean different things about how the cat is feeling depending on the situation.

Cats certainly do seem to slow blink when comfortable and relaxed, but this might not be the whole story and we should perhaps be a little cautious in assuming a slow blink is always a sign of a happy cat. Interestingly, until very recently, this form of blinking between cats and humans had received very little scientific investigation. Thankfully, we now have two recently published papers that can help shed some light on the slow blink, and its importance as a form of communication and its impact on the recipient (both the cat and human).

So, what is a 'slow blink' exactly?

The authors of the studies describe the slow blink sequence as a series of half-blinks, where the eyelids move towards each other but the eyes do not fully close, followed by either prolonged  narrowing of the eyes or a full eye closure.

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What were the aims of these studies and what did they do?

In the first study, the researchers aimed to investigate the potential communicative function of the slow blink when performed by cats and humans towards each other.

In the second study, the researchers also aimed to determine the impact of these slow blink interactions on cats’ chances of being adopted when housed in a rehoming centre.

Study 1:

In their first experiment, the researchers enlisted 21 adult cats (10 male, 11 female) and their owners, across 14 different households (some owners had more than one cat enrolled in the study).

All observations took place in the cats’ homes so they would feel comfortable and so that the experiments would take place under real life or ‘ecologically valid’ conditions.

The researchers asked the owners to perform slow blinks towards their cats and recorded the cats’ responses to these blinks. They also filmed the cats when their owners were ignoring them to act as a ‘control’ so that the cats’ responses could be compared across both these conditions.

Once collected, video footage of the cats’ facial responses was studied using the Facial Action Coding system for cats (catFACS).

CatFACS is a training manual specially designed to help researchers precisely code the facial movements and expressions most commonly displayed by cats. Facial expressions can be very difficult to measure and quantify, therefore using the catFACS ensured the cats’ facial movements could be documented in an objective, scientific way.

A further 24 adult cats (12 male, 12 female) were then recruited for their second experiment which also took place in owners’ homes and followed a similar protocol. This time, however, the experimenters were the ones doing the blinking, in order to see how cats would respond when it was performed by an unfamiliar person rather  than the cats’ owners. The researchers knelt down opposite the cat, offered their hand, and called its name. They then either adopted a neutral facial expression or performed a series of slow blinks towards the cat. Cats’ responses were again filmed and coded in a similar way to those in experiment 1.

Study 2:

The researchers recruited 18 adult cats (nine male, nine female) from Cats Protection’s National Cat Adoption Centre (NCAC) in Sussex. Of these study cats, eight had previously been identified as showing signs of anxiety (such as hiding and reluctance to eat or drink) and 14 had already been reserved to be rehomed. The study followed a similar format to the previous experiments, but this time the experimenter sat in front of each cat’s individual pen and performed either a series of slow blinks or had a neutral facial expression.

What were the main findings? Study 1: 

The researchers found that cats tended to respond to their blinking owners by reciprocating with similar eye movements. They found that cats performed more half blinks and narrowed their eyes more when their owners were blinking at them, compared to when their owners had a neutral (non-blinking) expression.

In this regard, they found that male cats were particularly responsive to owners’ blinking, and female cats less so. Interestingly, a similar effect was not detected for ‘full blinks’ (where the eye fully closes) — cats did not perform this type of blinking more when their owners were slow blinking at them.

A similar effect was observed when the experimenters (rather than owners) performed slow blinks towards cats — again, cats responded with more half blinks and eye narrowing. Cats  were also more likely to approach the experimenter after they had slow blinked at the cats, compared to when the experimenter had a neutral facial expression.

There was no effect of the cats’ gender this time, with male and female cats responding similarly.

Study 2:

Similar to the first study, cats in the rehoming centre performed half blinks more frequently and for longer durations in the situation where the experimenter was slow blinking at them. They also narrowed their eyes more. 

Interestingly, cats that fully closed their eyes more often in response to the experimenters’ slow blinking had a lower ‘time to adoption’, meaning these cats were selected more quickly by prospective adopters.

Additionally, the researchers also identified a trend (approaching statistical significance) for cats from the anxious cat group to perform elements of the slow blinking sequence (i.e. half blinking, eye narrowing, and eye closing) for longer durations than the non-anxious cats when in the proximity of the researcher.

Why is this research useful?

These studies indicate that both cats and humans may perceive being slow blinked at by the other as a positive social signal. These special ‘eye messages’ from humans seem to be consistently understood by cats, even when the blinks are performed by someone they don’t know (i.e. an experimenter) and in less familiar or more unstable environments (i.e. the rehoming centre).

In response to the slow-blinking humans, cats performed similar blinking behaviours and were also keener to approach and interact with them. Humans also seem to respond positively to cats’ slow blinking, as those that blinked (and fully closed their eyes) for longer appeared to be rehomed quicker.

Interestingly, the studies also suggest that for some cats, slow blinking at humans might be linked to them feeling anxious. However, as these studies only focused on the cats’ eye movements, it’s not possible to know if the slow blinking in the anxious cats was also accompanied by other behavioural signs of anxiety or discomfort.

This would certainly be an important line of future investigation and potentially help us to better understand the differences between a comfortable and uncomfortable slow-blinking cat.

So, why do cats slow blink and what does it actually mean? 

The action of slow blinking causes a softening of the gaze. As direct eye contact is something that cats may perceive as threatening, slow blinking could be a way for cats to signal that they ‘mean no harm’ or perhaps that its ‘safe to approach’. At the same time, they can still keep their eye on the person in front of them (just in case!), which is not possible if they fully broke their gaze by looking or turning their head away.

Slow blinking might also be an indication that the cat is relaxed or experiencing other positive emotions. For example, similar eye narrowing movements have  been observed in other species such as dogs, horses, and cows when experiencing pleasure. They can also be seen in humans’ faces when we perform ‘happy’ smiles (as opposed to forced ones!).

Both of these explanations could potentially be correct. Perhaps the communicative message behind a slow blink is always similar (e.g. ‘I’m not a threat to you’), regardless of whether the cat is actually feeling comfortable at the time. This theory would also fit with the finding that cats were more likely to approach a stranger when that person was slow blinking at them.

However, what the slow blink means about the cats’ emotional state may vary — in certain situations it may indeed be linked to happiness and in others possibly conflict or anxiety. Indeed, sometimes it may be as, if not more, important, to signal you’re not a threat when approached by a large, scary looking person, than it is when you’re receiving chin tickles from your favourite human.

What are the take home messages?

It certainly seems that both cats and humans interpret the slow blink as a positive form of communication. When looking directly at a cat, it’s therefore a good idea to keep your eyes slightly narrowed rather than having them fully open. Additionally, if you notice a cat that seems a little uncomfortable in your presence, performing a series of slow blink sequences (i.e. half blinking, keeping your eyes narrowed and then closing your eyes) may be a very good way to provide them with some reassurance.

This is certainly preferable to approaching or trying to touch or pick the cat up if they seem a little unsure. The study suggested that cats will use our slow blinking as an invitation to approach, meaning this is a sufficient prompt without us needing to go overboard with our encouragements!

The fact that cats performing aspects of the slow blink were adopted more quickly suggests that we might find this an appealing behaviour. This could be due to the popular notion that slow blinking cats are happy, friendly cats.

However, as highlighted by some of the study results, this might not always be the case. We should therefore be mindful that just because a cat slow blinks at us, it doesn’t necessarily mean they are feeling at ease. It’s therefore really important that we pay close attention to other details of their facial expression, posture, and behaviour (see those mentioned in the beginning of this article) before coming to any conclusions regarding how they may be feeling.