Why Do Dogs Blink? An Investigation of Canine Blinking

Do dogs blink and, if so, how does their blinking behavior differ from that of humans? Dogs blink, but they blink much less frequently than humans. While people blink 15-20 times a minute, dogs blink an average of 1-2 times a minute. This is due in part to the fact that dogs have a third eyelid that helps keep their eyes moist between blinks.

To learn more about how dogs blink and what their blinking behavior means, we will review studies of eye anatomy and behavioral research on dogs as well as a range of other species. By looking at the characteristics of blinking in different animals, we can learn a lot about the evolution and function of blinking behavior and its relationship to cognition. This will give us a more complex understanding of the apparently simple act of blinking.

The Biological Reason Dogs Don't Blink as Much as Humans

The biological reason that dogs don't blink as much as humans has to do with the differences in their eye anatomy. Dogs have a third eyelid called the nictitating membrane, which moves from side to side across the eye to provide extra moisture and protection. This means that dogs don't need to blink as much as humans because their eyes are constantly being kept moist by this extra membrane.

In contrast to humans, who blink 15-20 times a minute, a study in the Journal of Veterinary Behavior found that dogs blink between 2.5 and 14.5 times a minute under normal circumstances. Just like in humans, external factors like wind, dust, and allergens can affect how often a dog blinks. However, a dog's emotional state and focus can also affect their blink rate, with dogs blinking less when they are focused on something.

Sometimes changes in a dog's blink rate can be a sign of a health problem. For example, keratoconjunctivitis sicca (KCS) is a condition in which a lack of tear production leads to dry eyes. Symptoms including thick discharge, corneal ulcers, and changes in blink rate can lead veterinarians to assess the quality of a dog's tear film using tests like tear breakup time. While the biological reason for dogs' blink rates is rooted in evolution, understanding the biological reasons for the behavior can help us better understand the messages dogs are sending when they blink.

What Evolutionary Biology Can Tell Us About Dog Eye-Blinking

To better understand why dogs blink, it’s helpful to look at the evolution of this behavior across species. A comparison of dog eye-blinking to that of their closest evolutionary relatives, primates, can offer some interesting clues.

A wide-ranging analysis of eye-blinking in 71 primate species found that the frequency of eye-blinking is closely related to a number of factors, including body size and social structure. For example, diurnal primates (those that are active during the day) had higher rates of eye-blinking than nocturnal primates. The study also found that the number of blinks increased with group size, even when the researchers controlled for body size, which suggests that eye-blinking may have a social communicative function in primates.

The researchers also observed that nocturnal animals, including both mammals and birds, blink much less frequently than diurnal animals. This is consistent with the fact that dogs only blink 1-2 times a minute, while humans blink 15-20 times a minute. This difference is likely an adaptation to the lifestyle of the species, with the nictitating membrane helping to keep the eyes moist in dogs.

More clues come from studies of amphibious fish, such as the mudskipper. These studies have shown that these fish, which live both in water and on land, have evolved a blinking behavior that serves the same functions in tetrapods—moistening, cleaning, and protecting the eyes. This suggests that the evolution of blinking may be tied to the transition to life on land, a major evolutionary step that dogs and humans have in common.

In the end, the wide range of eye-blinking in different species suggests that it’s an important adaptation that may be related to a number of factors, including social behavior, sensory requirements, and the challenges of moving from water to land. Understanding these evolutionary factors can help us better understand the eye-blinking behavior we see in our dogs.

Blinking as a Way Dogs Communicate With Humans

Blinking is one of the many non-verbal ways dogs communicate with their human friends. A recent study even found that dogs and their owners engage in mutual eyeblink synchronization, with dogs blinking about a second after their owner or a stranger blinks. However, the owner blinks immediately after the dog blinks, while the stranger takes longer to blink.

This mutual blink synchronization is thought to help dogs and their owners understand each other and bond. Research has also found that when dogs look into their owner's eyes, it can lead to the human releasing more oxytocin. Often referred to as the "love hormone," oxytocin is important in maternal behaviors and social connections. This oxytocin-mediated positive feedback loop helps build the bond between dogs and their human parents.

Owners can also learn a lot about their dog's emotional state and intentions by paying attention to their blinking behavior. For example, experts say that slow, exaggerated blinking may be a calming signal or an attempt to negotiate, while fast, frequent blinking may indicate a dog is feeling stressed or fearful. Understanding these cues and incorporating them into their interactions with their pets can help owners better communicate with their dogs.

Clinical Applications in Veterinary Medicine

The ability to monitor and assess a dog's blink rate can be used to evaluate their health and well-being. A systematic review published in the journal Physiology & Behavior found that monitoring dog behaviors, including blinking, can be used to assess their welfare in a variety of situations, including veterinary clinics and animal-assisted interventions.

Changes in a dog's blink rate can also be used to detect potential health problems or pain. For instance, keratoconjunctivitis sicca (KCS), a condition that causes dry eye in dogs, is often associated with clinical signs such as thick discharge, corneal ulcers, and abnormal blink rates. In this case, veterinarians can diagnose and treat the condition by evaluating blink rates and other factors, such as tear breakup time.

Recent studies on the assessment of dogs' emotions and facial expressions have shown that regular eye exams and monitoring of blink rates should be part of routine veterinary care. By learning about the biological and evolutionary factors that influence dogs' blinking, veterinarians can better understand the behavior and use it to detect and treat potential health issues in their dog patients.

Conclusion: What Canine Blinking Means

This article has delved into the world of dog blinking, covering the biological, evolutionary, and communicative aspects of this simple behavior. Dogs blink much less frequently than humans, and this difference is largely due to the anatomy of their eyes and the presence of a nictitating membrane.

The many factors that influence dog blinking, from environmental factors to emotional states, can be used to improve dog-human communication and deepen the bond between people and their dogs. The interspecies eyeblink synchronization that was observed between humans and their dogs or cats shows that blinking plays a role in forming positive emotional connections.

In addition to these insights, the study of dog blinking has the potential to improve veterinary care. By monitoring changes in blinking patterns, veterinarians can catch a variety of eye conditions early, which can lead to better outcomes for dogs and cats.

As we learn more about the cognitive and behavioral abilities of animals, the study of blinking and interspecies eyeblink synchronization provides a unique perspective on the evolutionary and communicative abilities of dogs. By taking this information into account, we can build a deeper understanding of dogs and cats, improve our interactions with them, and gain a greater appreciation for the amazing adaptations that have made dogs such an important part of human history.