Why Optic Flow Restores Us

Boosting optic flow is a powerful and effective way to nourish physical and emotional well-being. Optic flow refers to the unique sensation that occurs when you perceive your environment actively moving in relationship to your body’s movements.

What’s at play here? As you walk, bike, run, or swim, objects in your environment appear to move. During a walk, for example, objects grow larger as you approach; this lets you know you’re getting closer. During a swim, you perceive the bottom of the pool (or lake or ocean) receding underneath you, or objects on the side moving as you turn your head to breathe. In optic flow your eyes move, continually updating your brain on your location.

That’s not all optic flow does for you.

Your visual system links closely with (read: is part of) your autonomic nervous system. Activating your sympathetic (fight-or-flight) nervous system ignites the stress response. This dilates your pupils and narrows your field of focus. Your parasympathetic system, in contrast, constricts your pupils and broadens your focus.

Narrowly focused vision, the kind you use when concentrating on work (or, um, a computer screen or phone) dilates your pupils and ignites sympathetic activation. This gives you the mild arousal you need to pay attention. Stay locked in high-focus visual perception too long, though, and you can experience feelings of anxiety, stress, hypervigilance, and irritability. (See the part of the next section that explores BRAC, your Basic Rest and Activity Cycle, which unpacks this further.)

When you look at the horizon or at a broad vista without focusing narrowly and while taking in your periphery, your pupils constrict. This activates your parasympathetic (rest-and-digest) nervous system. As your eyes move from left to right and up and down and forward in optic flow (panoramic vision), the brain’s stress response quiets.

We know about the strong relationship between vision (or audition) and stress management not just because of neuroscience, but thanks to the tireless efforts of Francine Shapiro. One sunny May afternoon in 1987, Shapiro found herself troubled by disturbing memories. A graduate student in psychology, Shapiro went for a walk in a nearby San Diego park when she made an accidental and astonishing discovery: While recalling the incident, her eyes moved rapidly from side to side. Afterward, the disturbing memories were markedly less intrusive. Shapiro summoned another traumatic memory and moved her eyes in the same way; amazingly, the memory became less disturbing. After writing her Ph.D. thesis on the effect, Shapiro founded the field of EMDR (Eye Movement Desensitization and Reprocessing). Despite skeptics, Shapiro worked hard to legitimize the technique. In 2013, the World Health Organization approved EMDR for use in treating PTSD and other mental health disorders. And independent researchers have demonstrated its efficacy with PTSD.

You can also get some optic flow by walking indoors, e.g. throughout your home. It doesn’t depend on vision: for blind people, optic flow occurs aurally, through sound.

Walking at night is less effective for optic flow. (That’s OK; we don’t need walks to do everything! Plus, night walks can be beneficial, particularly to offload glucose and help digest your last meal of the day; this promotes deeper sleep.) You’ll also find that movement feels more effortful at night. This is because when you move in the dark, you see only objects that are close to you. This decreases the speed of optic flow, causing the sensation that you’re working harder and going farther.

Your body’s movement provides the key mechanism for optic flow. A car, train, or motorcycle may give you pleasure or a mode of transport, but won’t boost your optic flow. A treadmill, stationary bike (yes, even Peloton!), yoga, or other forms of indoor fitness are great in many other ways, but won’t offer the continuous forward movement that characterizes optic flow.

Self-generated optic flow gives you moment-to-moment updates on where your body is located in space. It provides input on the orientation, coordination, and balance of your body as you move. It informs you about your balance, postural control, and the layout of your environment. In these ways, optic flow strengthens proprioception, your sixth inner body sense. (Before finalizing, I verified this with Alexander Borst of the Max Planck Institute.)

My strong personal conviction: Because its effects are strongest and most therapeutic when movement is initiated and maintained by us, optic flow supports body agency, the ability to initiate and to act in a way that matches our intentions. It is also vital to lifting depression and therefore, alleviating seasonal affective disorder.

Moving outside (walking, running, biking, swimming. etc.) sis an ideal way to get light + optic flow at the same time.

Throughout the pandemic, I’ve relied on walking, swimming, and sometimes running for optic flow more than usual. It’s amazing; it resets my mental and emotional state, especially when I build it in consciously.

Tip: when you walk, bike, swim, or run, take time periodically to check in with your vision. Consider promoting deliberate awareness of optic flow every so often—it’s easy and fun! (When I swim indoors in fall, winter, and spring, the bottom of the pool sometimes appears stationary; I take a moment, when turning my head, to register the side of the building “moving” as I go past.)

If you love to listen to podcasts while you move outdoors, check to see that your gaze is panoramic rather than focused, at least for a chunk of time. If it’s too focused, consider taking your earbuds out every other time. Also, since optic flow can happen aurally, taking an earbud break can help you boost it; plus, you’ll be able to hear the sounds of nature, too.

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