Every inhale and exhale subtly reshapes what you see—a discovery that could transform how we understand perception, attention, and even diagnose neurological disorders.
Have you ever noticed that sometimes you can see details with crystal clarity, while other moments your vision seems optimized for spotting movement or faint objects in dim light?
As it turns out, this shift might be happening with every breath you take.
For over a century, scientists believed that only three factors controlled pupil size: light levels, focus distance, and cognitive processes like emotions or mental effort. But groundbreaking research from Sweden’s Karolinska Institutet has uncovered a fourth fundamental factor that’s been hiding in plain sight: your breathing rhythm.
This unexpected connection reveals that your pupils are smallest when you inhale and largest when you exhale—a continuous cycle that subtly transforms your visual perception roughly 12-16 times every minute.
“When we began this research, we weren’t specifically looking for this connection,” explains Dr. Artin Arshamian, associate professor at Karolinska Institutet’s Department of Clinical Neuroscience. “But the data was unmistakable. Your breathing pattern is constantly fine-tuning your visual system in a way nobody predicted.”
How Your Breathing Reshapes What You See
The research team, led by Arshamian and postdoctoral researcher Dr. Martin Schaefer, conducted five meticulous experiments involving over 200 participants to confirm their unexpected discovery. Their findings, published in The Journal of Physiology, demonstrate that this breathing-vision connection persists across numerous conditions:
- Whether breathing quickly or slowly
- Through the nose or mouth
- In bright or dim lighting
- At rest or while engaged in visual tasks
Just as a camera’s aperture controls both light intake and depth of field, your pupils perform the same function for your eyes. During inhalation, your pupils constrict slightly, creating an effect similar to squinting—enhancing your ability to perceive fine details and improving depth perception.
During exhalation, your pupils dilate, allowing more light to enter and making your visual system more sensitive to faint objects or movement, particularly in low-light conditions.
“Our results suggest that our vision alternates between optimizing for distinguishing small details when we inhale and detecting faint objects when we exhale, all within a single breathing cycle,” Schaefer explains.
“It’s as if nature built in a rapid-fire toggle switch that constantly fine-tunes our vision for different scenarios.”
How the Brain Synchronizes Breath and Vision
This discovery builds upon an emerging understanding that breathing does far more than just oxygenate the body. Recent neuroscience research has revealed that respiration generates rhythmic electrical activity—neural oscillations—that influence numerous cognitive and perceptual processes.
These oscillations originate from two primary sources:
- The preBötzinger complex, a cluster of neurons in the brainstem that regulates breathing rhythms
- The olfactory bulb, which processes smell and responds to air movement through the nasal passages
Previous studies with animals have demonstrated that these breathing-linked oscillations help synchronize various sensory and motor behaviors—from sniffing and whisker movements in rodents to subtle head movements in humans.
One of the study’s most surprising findings was that this pupil-breathing connection persisted even in individuals born without an olfactory bulb, suggesting that the brainstem alone may regulate this effect—highlighting its deep evolutionary origins.
“The fact that this connection exists in people without an olfactory bulb suggests this mechanism evolved very early in our lineage,” notes Arshamian. “It may represent a fundamental way that vertebrate brains coordinate sensory systems with breathing.”
From Daily Tasks to Medical Breakthroughs
The research raises fascinating possibilities about how breathing patterns might subtly influence everyday visual activities.
Tasks requiring precision focus—like threading a needle, reading fine print, or detailed computer work—might theoretically benefit from controlled inhalation. Conversely, activities like nighttime driving or spotting distant movement might be enhanced during exhalation phases.
Dr. Eliza Thornton, a neurologist at Stanford University not involved in the study, finds the potential clinical applications particularly exciting.
“The autonomic nervous system controls both pupillary response and breathing,” Thornton explains. “Abnormalities in this system often signal neurological disorders. This discovery could potentially provide a new, non-invasive metric for diagnosing conditions like Parkinson’s disease, where pupillary dysfunction often appears before more obvious symptoms.”
Arshamian agrees: “One potential application is developing new methods to diagnose or treat neurological conditions such as Parkinson’s disease, where damage to pupil function is an early sign of the disease. This is something we want to explore in the future.”
Attention, Concentration, and Performance
The discovery may also help explain why certain breathing techniques have been used for centuries in practices like meditation, yoga, and martial arts to enhance attention and performance.
Dr. Rishi Kumar, a cognitive neuroscientist specializing in attention at University of California, Berkeley, notes that this research provides a potential neurobiological explanation for these ancient practices.
“Many meditation traditions emphasize specific breathing patterns, and practitioners report enhanced visual awareness,” says Kumar. “This research suggests that controlling breathing rhythms might directly influence visual processing and attention in ways we’re just beginning to understand scientifically.”
For example, the study might help explain why controlled breathing exercises help competitive athletes, performers, and even public speakers achieve what psychologists call “flow states”—periods of heightened focus and performance.
“When we’re anxious, our breathing becomes shallow and rapid, which may disrupt the natural pupillary rhythm,” Kumar adds. “By consciously regulating breathing, we might be directly influencing visual processing in ways that enhance performance.”
Building on a Century of Vision Science
The discovery adds a new dimension to our understanding of human vision, which has evolved dramatically over the past century.
Early vision researchers established that pupil size changes in response to light levels—contracting in brightness and dilating in darkness—a reflex that optimizes light intake. Later studies revealed that pupils also respond to focus distance and cognitive factors like mental effort, emotional state, and interest.
Now, breathing joins this list as a fourth fundamental influence, one that operates continuously throughout daily life.
“What makes this mechanism unique is that it’s cyclical, ever-present, and requires no external stimulus,” says Arshamian. “Since breathing affects brain activity and cognitive functions, the discovery may contribute to a better understanding of how our vision and attention are regulated as a whole.”
Future Research Directions
The research opens numerous avenues for future exploration. Key questions researchers plan to investigate include:
- How does the strength of this breathing-pupil connection vary across individuals?
- Can people learn to consciously control this mechanism for enhanced visual performance?
- How might this connection be harnessed for clinical diagnostics or treatments?
- Does the effect differ in people with respiratory conditions like asthma or COPD?
- Could specialized breathing techniques enhance specific visual tasks?
Some breathing techniques, like the Wim Hof method or pranayama yoga practices, involve controlling breath timing and depth. Researchers now wonder if these practices might inadvertently be modulating visual perception as well.
“We’re particularly interested in exploring whether certain breathing patterns might be beneficial for specific visual tasks,” notes Schaefer. “For instance, could controlled breathing enhance a surgeon’s precision or a pilot’s ability to spot distant objects?”
A Broader Scientific Revolution: The Brain-Body Connection
This discovery is part of a broader scientific revolution in how we understand the relationship between breathing, the brain, and cognition.
Recent research has already established connections between breathing and memory formation, emotional regulation, and even pain perception. The addition of vision to this list suggests that breathing may be a master regulator of numerous brain functions.
“For decades, neuroscience treated the brain as somewhat separate from the body,” explains Dr. Kumar. “Now we’re seeing that physiological processes like breathing create cascading effects throughout the brain’s neural networks. It’s a paradigm shift in how we think about cognition.”
This holistic perspective aligns with traditions like Chinese medicine and yoga, which have long emphasized the central importance of breath regulation for overall wellbeing.
Can You Use This Discovery?
While research into practical applications remains in early stages, some potential ways to apply this knowledge might include:
- Reading and detailed work: Consider the possibility that inhaling slightly while performing detail-oriented visual tasks might enhance your ability to see fine details.
- Night driving or low-light situations: Being aware that your vision might be slightly more sensitive to movement and faint objects during exhale phases.
- Meditation and focus: The research provides additional scientific context for why focusing on breath might enhance attention and visual awareness.
- Digital eye strain: Taking regular breathing breaks when working on computers might help regulate pupil fluctuations that contribute to eye fatigue.
However, Arshamian cautions against overstating immediate practical applications: “The effect is subtle, and we’re still exploring its practical significance. While fascinating from a scientific perspective, more research is needed before we can make specific recommendations about consciously using this mechanism.”
A Timeless Connection, Hidden in Plain Sight
Perhaps most remarkable about this discovery is that it reveals a fundamental connection that has likely existed throughout human evolution—one that influences how we perceive the world roughly 20,000 times per day, yet remained scientifically undocumented until now.
“It’s humbling to realize that basic aspects of human perception can still remain undiscovered in the 21st century,” reflects Arshamian. “It makes you wonder what other fundamental connections we’ve yet to notice.”
The research underscores how deeply integrated our physiological systems are—a symphony of interconnected processes that continuously shape our experience of the world around us.
As you read these words, your pupils are already responding to this rhythm—contracting slightly as you inhale, expanding as you exhale—subtly transforming what and how you see with every breath.
References
Schaefer, M., et al. (2025). Respiration-induced pupil size fluctuations enhance visual processing. The Journal of Physiology.
Arshamian, A., et al. (2024). Respiratory rhythms in neural oscillations and their influence on sensory processing. Trends in Neurosciences.
Zelano, C., et al. (2023). Nasal respiration entrains human limbic oscillations and modulates cognitive function. Journal of Neuroscience.
Yackle, K., et al. (2022). The preBötzinger complex and its role in generating breathing-linked neural oscillations. Nature Reviews Neuroscience.
Shipp, S. (2022). The pupillary light reflex pathway: A review of recent advances in understanding its neural mechanisms. Annual Review of Vision Science.
Del Negro, C.A., et al. (2021). Breathing matters. Nature Reviews Neuroscience.
