Most people who can only wink one eye have nothing wrong with their facial nerves. The asymmetry comes from how your brain controls each side of your face differently, combined with natural variation in facial nerve anatomy and motor skills you developed (or didn’t) as a child. Your brain’s default setting is to blink both eyes together; winking is an active override of that program, and it turns out that override works better on one side for most people.
What Winking Actually Demands From Your Brain
A blink looks simple, but the neural machinery behind it is surprisingly complex. Two sets of muscles around each eye work against each other: one circles the eye socket and squeezes it shut, while another lifts the upper lid and holds it open. During a normal blink, both sides fire together in a synchronized pattern governed by circuits spread across the cortex, deeper brain structures, and the brainstem.1Clinical Neurophysiology. Neural control of blinking The whole thing happens automatically and symmetrically, which is exactly the problem when you try to wink.
Winking requires you to break that symmetry on purpose. You need to activate the closing muscle on one side while simultaneously suppressing it on the other, and keep the lifting muscle engaged on the eye that stays open. That is a much harder ask than a bilateral blink, because your brain has to override its own deeply ingrained reflex to close both eyes at once. Think of it like trying to pat your head and rub your stomach: the challenge is not in either motion alone, but in sending different commands to two sides at the same time. When one side consistently fails at this trick, it usually means the neural pathways responsible for that independent override are less developed or less efficient on that side.
The Handedness Connection
If you are right-handed and find it easier to wink your left eye (or vice versa), you are not imagining it. The same brain lateralization that makes you favor one hand for writing and throwing also creates lopsided motor control across your face. Your brain’s left hemisphere primarily controls the right side of your body and the right hemisphere controls the left, but facial muscles have a more complicated arrangement. For deliberate, voluntary movements of just one side of the face, the evidence consistently points to a contralateral pattern linked to handedness.
A study measuring deliberate unilateral facial movements found a significant inverse relationship between handedness and which side of the face performed better.2PubMed. Asymmetry of facial expression related to handedness, footedness, and eyedness: a quantitative study A separate investigation put numbers to this: roughly 59% of right-handed people found it easier to perform facial exercises with the left side of their face, while about 73% of left-handed people performed better with the right side.3PubMed. Functional asymmetry in the face The pattern was even more pronounced among left-handers. So if you are right-handed and your left-eye wink is the easy one, the odds are that your brain’s lateralization is driving that preference.
More recent research has confirmed that handedness shapes facial asymmetry in structural ways too. Right-handed individuals tend to have slightly more prominent features on the right side of their face, while left-handed individuals and males often show greater prominence on the left.4PubMed Central. The relationship between facial directional asymmetry, handedness, chewing side preference, and eyedness These are subtle structural differences, but they reflect the deeper reality that your two hemispheres do not invest equally in controlling each side of your face.
Eye Dominance and the Eye That Refuses to Wink
You have a dominant eye just like you have a dominant hand, and it plays a specific role in which eye you struggle to wink. A study of students who could only wink one eye found that, consistently, the eye they could not wink was their dominant eye.5PubMed. Inability to wink an eye and eye dominance In other words, the eye your brain relies on for tasks like sighting down a camera viewfinder or lining up a target is the one it most resists shutting voluntarily.
This makes intuitive sense once you think about it. Your dominant eye is the one your visual system prioritizes, the one your brain treats as the primary source of spatial information. Closing it on command means deliberately shutting off your most-trusted visual input, and your brain pushes back against that. The non-dominant eye, by contrast, is more expendable from a sensory standpoint, so your brain has an easier time letting it close independently. If you want to test this, try the simple “triangle” test: extend your arms, overlap your hands to form a small triangle, and look at a distant object through it with both eyes open. Close one eye at a time, and whichever eye keeps the object centered in the triangle is your dominant eye. There is a good chance it is also your hard-to-wink eye.
Your Facial Nerve Is Not Symmetrical
Even if brain lateralization and eye dominance explained everything, you would still expect some variation from person to person, because the facial nerve itself is wildly variable in its anatomy. After the facial nerve exits the skull, it fans out into branches that control different zones of the face. The branching pattern of that nerve is not standard from one person to the next, or even from one side of the same person’s face to the other.
A detailed dissection study of facial nerves identified 12 distinct branching patterns, and the two most common types each showed up in only about 21% of cases.6PubMed. Extracranial Course of the Facial Nerve Revisited Some patterns involved simple connections between a few branches, while others formed complex networks linking four or more branches together. The number of terminal branches reaching the muscles was described as highly variable. What this means for winking is that the nerve supply to the muscles around your left eye may be wired quite differently from the supply on your right. One side might have more cross-connections between branches, giving it more redundancy and finer control, while the other has a sparser network that makes isolated movements harder.
This kind of anatomical variation is invisible to you. You cannot feel or observe your nerve branching pattern. But it helps explain why some people can wink both eyes easily, some can only manage one, and a small number struggle with both. The underlying hardware is just different from person to person.
Children Have to Learn This Skill
If you are watching a young child try to wink and failing adorably, there is a good reason. The ability to close one eye while keeping the other open is not innate. It is a learned motor skill that develops through childhood in a predictable sequence.
Research tracking how children learn to use one eye found four distinct stages. At around age three, children place a viewing tube at the midline of their head and keep both eyes open. By about age five or six, they shift the tube toward one eye but still keep both eyes open. Around age seven, they start turning their head to compensate. It is not until roughly age nine or ten, on average, that children consistently close the non-viewing eye, the response adults take for granted.7Vision Research. Learning to Look With One Eye: The Use of Head Turn by Normals and Strabismics
The progression reveals something important: shutting one eye independently is not a basic motor reflex that everyone is born with. It is a sophisticated skill that requires years of neural maturation and practice. Some children reach the adult stage earlier than others, and some adults who never had much reason to practice one-sided eye closure may retain a mild version of an earlier developmental stage on their weaker side. If you can wink one eye but the other side just scrunches your whole face, you may have simply never built the neural pathways for that specific motion as thoroughly during childhood.
Can You Train Your Weaker Side?
The short answer is: probably, at least to some degree. Facial muscles respond to repetitive exercise much like other muscles, and the neural pathways controlling fine motor skills can be strengthened with practice. That said, there are real limits set by anatomy.
One challenge is fatigue. Facial muscles tire faster than you might expect during sustained effort. A study measuring how quickly facial muscles lose strength found that sustained contraction led to significant declines in muscle activity: roughly 35% for brow raising, 23% for smiling, and 29% for lip pursing.8Archives of Physical Medicine and Rehabilitation. Measuring fatigue related to facial muscle function This means your practice sessions should be short and frequent rather than marathon attempts. If you try to force your weaker side for too long, the muscles tire out and the quality of the motion gets worse, not better.
People who have trained themselves to wink their difficult eye generally describe a process of gradual isolation. You start by holding the easy-wink eye open with a finger while practicing closing the other. Over time, you try to replicate that motion without the finger assist. The brain eventually builds stronger pathways for the independent command. Some people achieve a smooth wink on both sides within a few weeks of daily practice; others reach a functional but slightly awkward version; and some never quite get there. The underlying nerve anatomy and degree of brain lateralization set a ceiling that practice alone may not overcome.
The Role of Motor Overflow
When you try to wink your difficult eye and your entire face scrunches up, or the other eye closes too, you are experiencing motor overflow. This is when a command intended for one set of muscles leaks into neighboring muscles that you did not mean to activate. It is the same phenomenon that makes children stick their tongues out while concentrating on cutting with scissors.
Motor overflow is especially common in the face because the muscles are packed tightly together and many of them share nerve branches. The circular muscle around your eye does not operate in perfect isolation; it has connections to muscles in your cheek, forehead, and nose. When your brain sends a strong “close this eye” signal down a side with less refined neural control, the signal bleeds into adjacent muscles. Your forehead furrows, your cheek lifts, your nostril flares, and the whole effort is visible as a grimace rather than a clean wink. On your good side, the neural pathways have been refined enough to send a more targeted signal with less spillover.
This is also why people who are very expressive or who use a lot of facial gestures sometimes have an easier time with bilateral winking. They have spent years sending fine-tuned, independent commands to their facial muscles, which gradually reduces overflow on both sides.
When One-Sided Difficulty Might Signal Something Medical
For most people, the inability to wink one eye is a benign quirk, not a medical concern. But there are situations where a change in winking ability, or unusual movements linked to winking, should prompt a conversation with a doctor.
Facial synkinesis is a condition where a voluntary movement of one facial muscle triggers an involuntary contraction of a different facial muscle. It most commonly develops as a result of moderate to severe facial palsy, such as Bell’s palsy, when the nerve regenerates but some fibers grow back along the wrong paths.9PubMed Central. Pathogenesis, diagnosis and therapy of facial synkinesis The result is that trying to close one eye might cause your mouth to twitch, or smiling might make your eye close. This aberrant nerve regeneration leads to involuntary co-movements that can affect facial expression and quality of life.10PubMed. Synkinesis after facial palsy
A rarer condition called Marcus Gunn jaw winking involves abnormal connections between the nerves controlling jaw movement and those controlling the eyelid. People with this condition may find that their eyelid rises when they chew, open their mouth wide, or suck through a straw. It is typically present from birth and results from prenatal wiring errors where nerve fibers meant for one muscle end up innervating another.11PubMed. Marcus Gunn jaw winking with trigemino-oculomotor synkinesis of the inferior division of the oculomotor nerve
The key distinction is between lifelong asymmetry and new-onset changes. If you have always been able to wink only one eye and nothing has changed, you are almost certainly dealing with normal neurological and anatomical variation. If you used to wink both eyes fine and now one side is weak or produces strange accompanying movements, that is worth investigating because it could indicate nerve damage, a recovering palsy, or a neurological issue affecting the facial nerve.
Why Faces Are Built for Symmetry, Not Independence
It helps to step back and consider what facial muscles evolved to do. Primate faces are primarily built for social communication: expressing emotions, mimicking others’ expressions, and directing gaze during interaction.12Current Opinion in Neurobiology. The many facets of facial interactions in mammals Almost all of those functions are bilateral. A genuine smile activates both sides of the mouth. A fearful expression raises both brows. Surprise widens both eyes. The neural architecture of the face evolved under pressure to produce symmetrical expressions, because lopsided expressions look unnatural and send confusing social signals.
Winking, by contrast, is a culturally specific gesture that has no deep evolutionary precedent. Your brain did not evolve under pressure to get good at it. The fact that most people can manage at least one side is more of a fortunate side effect of general motor sophistication than a purpose-built ability. Viewed this way, the real surprise is not that you can only wink one eye. It is that you can wink at all, given that the system was optimized for a very different set of tasks.
Sensory Feedback and Why the Mirror Helps
People trying to train their weaker wink often notice it is easier in front of a mirror. This is not just a psychological comfort. The sensory feedback loop for facial muscles is unusually weak compared to, say, your fingers. You have excellent proprioception in your hands and arms: even with your eyes closed, you know exactly where your fingers are and what they are doing. Your face has much less of this built-in position sensing. Research into the sensorimotor regulation of facial expression has identified this as a significant gap in our understanding of how people control their faces.13PubMed Central. Sensorimotor regulation of facial expression – An untouched frontier
Without strong internal feedback, your brain relies more heavily on visual confirmation (what you see in the mirror) and social feedback (other people’s reactions) to calibrate facial movements. When you practice winking in a mirror, you are essentially giving your brain the feedback it cannot generate internally. You see whether the correct eye closed, whether the other eye stayed open, and whether your whole face scrunched or stayed relaxed. Over time, that visual feedback helps your brain build a better internal model of the motion, which is partly why mirror practice tends to speed up the training process.
This weak proprioception also explains a common frustration: you think you are winking normally, but a friend tells you it looks more like a twitch or a squint. Without a mirror, your brain’s estimate of what your face is doing can be surprisingly inaccurate, especially on the side with less practiced control.