VISION AND MOTORCYCLING
Vision is not just about eyesight. It’s a lot more cerebral than it ‘seems’. The seeing is just a part of the story and a large half of it goes on inside the grey matter. Motorcycling depends on ‘seeing’. No matter what skills you have and hardware you ride, vision is the source matrix of every verb, adverb and adjective associated with biking, be it survival, fun, freedom, show-off, commute, life-style etc etc. You ride strictly and primarily in accordance with what you see. This article here is about knowing and understanding this process of sight and vision, biased towards benefiting us as motorcycle riders.
Text: Sandeep Goswami (Old Fox/xBhp)
The traditional measure of good eyesight is the standard eye-test that uses the Snellen eye chart and declares your prefect eye-sight as 20/20. (here 20/40 would mean ‘weak’ eyesight, the numbers implying that you can only see from 20 ft what someone with ‘normal’ eyesight can see from 40 ft away). Vision is not just for reading speedometers and tachometers when riding a bike. So just a measure of near or far sightedness that constitute ‘refractive errors ‘ which reduce ‘distance visual acuity’ and is correctible by wearing proper lenses is just a tiny part of the story. Vision is dynamic and it is this dynamic component that is of vital importance to a motorcyclist, driver, athlete, ballgame player, fighter pilot…..in short, practically everyone. As I had stated in my previous article on vision (Seeing is Believing, Hard Torque, October 2010 issue) “MAINTAINING VISUAL ACUITY IN AN ENVIRONMENT AS DYNAMIC AND SPONTANEOUS AS MOTORCYCLING REQUIRES MORE THAN MERE 20/20 VISION.”
Visual acuity or the ability of the eye to see clearly and for the brain to build a ‘realtime’ picture of one’s situation and environment requires a very close co-ordination between the eyes and the brain. We don’t ‘see’ with the eyes alone. The image built by the eye is processed by the brain, which refines it to make it congruent with the real world around us and it is this ‘edited’ image that we eventually get to ‘see’. The fact that the edges of a table remain straight and parallel, no matter how up-close you view them from is ample proof of some tweaking of the seen image by the brain. A pure picture of the table from up-close would show curvature of the far ends of the table’s edges as any curved lens gathering light distorts it around due to that curvature. The brain uses stored inputs from other senses (your hands tell you the edges are straight, the fact that the edge is at equal distance from the wall all along and so must be as straight as the wall etc etc) and your prior experience and refines the picture. This processing of the image before you get to ‘see’ it is where the benefits and traps of vision lie hidden for a motorcyclist.
Depth Perception or 3-D Vision
So let’s delve deeper into the mechanism of sight by the eyes and of the way the brain constructs that sight and converts it into useable intelligence. Among the major contributory sight mechanisms, stereoscopic vision is a major plus for any dynamic activity. It makes ‘depth perception’ possible. Stereoscopic vision involves synchronized use of both the eyes. Each eye sees the object in front at the same time but a little differently from the other. In layman’s terms, the left eye sees more of the left side of the object than the right does and vice-versa, the right eye sees more of the right side than the left eye does. These differing images are sent to the brain which processes them and builds up a 3-D composite image that you finally get to ‘see’. Depth perception allows you to gauge the exact distance between you and the object with millimetric accuracy, to update you about any change in this distance as the object moves away from or towards you and to even judge the extent of empty space between you and the object. The eyes-brain combo allows this to be done many times over in a second to give dynamic 3-D vision. You wouldn’t be able to catch that ball thrown towards you or enjoy movies like ‘Avatar’ was it not for stereoscopic 3-D vision.
Test yourself for 3-D Stereoscopic Vision: Place a magazine about 3ft in front of you and level with your eyes. Look at this black circle in fig 1. Now hold a pencil or a pen some 1 ½ ft in front, between your eyes and the magazine. With both eyes open, look at the pen. You’ll perceive the single black circle become two and appear on either side of the pen. Now stare at the black circle and you’ll see the single pen become two pens straddling the circle. Being able to see this ‘parallax induced effect’ means both your eyes are working together to make your 3-D stereoscopic vision functional.
Check which is your ‘Dominant Eye’: To check which eye is the ‘dominant’ one, overlap both hands with your arms extended in front of your face and leave a small hole, about an inch across, between the hands by sliding them apart. Look at a distant object through this hole with both eyes open. Now, without moving either your head or hands, close one eye at a time. The eye with which you can look at the object, i.e. the eye that lines up the object with the hole, is the dominant eye. See if it is on the same side as your dominant hand.
Dominant Eye
But do both the eyes always work together. No. In fact, one of the eyes is always the ‘dominant’ one while the other follows its movement as its slave. This ‘lead and follow’ thing induces a slight time difference between the vision through both eyes. The interesting thing of this ‘dominant eye’ stuff for a motorcyclist lays in the fact we all tend to have a dominant hand too. Meaning that we are either right handed or left handed (of course a few rare exceptions are ambidextrous but then let’s discuss the majority here, shall we?). The issue of interest for a motorcyclist resides in the fact that those of us who have the dominant eye on the same side as our dominant hand (i.e. if we are right handed and our right eye is the dominant eye), then we have a distinct advantage at hand-eye coordination in all things dynamic. Which means we are naturally equipped to be more skilled riders though how well we develop and use those skills are of course entirely upto our training, attitude and aptitude. The latter implication points to the fact that through the right training, attitude and aptitude, you can become a better rider than someone who has the ‘dominant eye/hand’ advantage.
Peripheral Vision
The human eye has two types of light receptor cells on the retina called rods and cones. Named so for their appearance under a microscope. Of these, the cone receptors are sensitive to colour while the rods are to low light and movement. Both have their own strengths and weaknesses. Cones require an appreciable amount of light to be able to distinguish colours and are located in a cluster occupying the middle of the retina. The rods surround the cones and are extremely sensitive light detectors. So sensitive that on a dark moonless night, they react to individual photons striking them and generate grainy noise in our vision. But that’s beside the point here. What’s important is that these rods are responsible for our peripheral vision. Their extreme sensitivity to changes in incident light makes them super-sensitive to detecting movement. That’s of great importance to a motorcyclist. Movement detected by our peripheral vision prompts us to direct our gaze at it and ‘resolve’ it into a clearer and more informative picture. The peripheral vision helps the motorcyclist monitor his immediate surroundings for movement without having to shift focus from a high threat area he is looking at.
Check your ‘Peripheral Vision’: Extend both arms along your sides, parallel to the ground, and keep those thumbs vertical. Looking straight ahead, without moving the head or the eyes, slowly start moving the hands in front together. The thumbs will creep into your awareness when the hands have moved some 6 inches or so. These mark the outer boundaries of your peripheral vision.
Improving ‘Peripheral Vision’: Sit in your room and while looking straight ahead without moving either your head or eyes, start making a mental list of all that you can see apart from straight ahead. Cross check by looking around. Do this in strange surroundings. Your list grows in length as your peripheral vision improves.
Tracking or Visual Pursuit
There are two parts to the mechanism of dynamic vision. One where we ‘acquire’ our object of interest through a visual search or scan. And second when we stare at it or ‘fixate’ on it to see or resolve it clearly by using our central or ‘foveal’ vision. The human eye has a very narrow field of focus, barely 3 deg which is about the width of your thumb held at an arm’s length in front of your eyes. No wonder we need to constantly move our eyes even while reading this one single sentence. This narrow focus is necessary to help the brain reproduce the ‘seen’ object in great detail. High resolution. But clearly we need to see more while riding. And for that the eye moves or tracks a moving object. This smooth ‘visual pursuit’ though is pretty slow by motorcycling standards, barely 70 degrees a second which equates to a person walking across, fast, a few feet away from you. Any faster than ~70 deg/sec and the brain would not be able to produce a 3D stereoscopic image that gives us depth perception.
Improving Tracking or Visual Pursuit ability: Make a friend move a pencil or a pen from left to right (or vice-versa) about 3-4 feet in front of your face and follow the movement just with your eyes, without moving your head.
Saccades
To improve its ability towards faster visual pursuit, the eye ‘saccades’. Saccades are a very rapid re-positioning of the eyes from one ‘fixation’ to the next. This movement can exceed even 700 degrees a second or is 10 times faster than smooth pursuit. Saccades are also often aided by head rotation when the arc of vision is greater than 20 deg or so. These saccades are so fast that all visual input to the brain ceases during it. This ‘saccadic suppression’ of vision during a saccade is a natural consequence of the fast eye movement. The image produced on the retina is a barely recognizable blur during it and of no use to us. So the brain blanks it out of our consciousness. But to maintain continuity of vision, the brain superimposes the last seen image on our sight and so we are not really aware of that momentary sightlessness. We get the impression that we were not momentarily blind while our eyeballs were moving but in fact we are. (Check this out by looking at your image in a mirror from one side to the other. You will never see your eye-balls moving while a friend watching you will do so.) Trouble is that this ‘saccadic suppression’ begins just before the actual saccade. And a rider saccading between the road and the tachometer will not see anything that happens in-between as the eyes are ‘switched off’ between ‘fixations’. To understand the gravity of the situation, imagine yourself riding down a good clean road at 80 kph (which equates to about 72 ft/sec). Imagine a saccade lasting some one-tenth of a second and within this time span you’ve traveled 8 ft. And were riding blind. Complicating the scenario further is the fact that we blink some 8-10 times a minute, each blink lasting anywhere between 1/3rd to 1/4th of a second. Again about 20ft blind during the blink. If you hit a saccade and a blink in tandem, then you’re blind for almost 30ft and anything could move in into your path during this time. This is where the story of that ‘blasted dog that came out of nowhere in front of my bike’ comes from.
The solution lies in what expert riders call ‘mind riding’. Bring the mind into the picture. Visual prediction, based on past experience, present alertness and future projection takes the rider ahead in time, helping him predict the possible outcome. He has to be in the ‘groove’ while riding, observing, analyzing, evaluating and predicting all that goes on around him. Visualize the route you shall take before you begin the ride. Imagine yourself moving firmly and resolutely through traffic, adding situations from your familiarity with the route and past riding experiences. The brain gets kick-started into the ride by the time you kick-start your bike. And it begins working on the ‘predicting’ just as you slide the Bike into first gear. Expectation will not only make you look in the generally correct direction but will also reduce the actual processing time of the brain. Some even call it the ‘sixth sense’ while in fact, it is the optimized use of one of the five senses, the sight.
Fixations
Fixations occur when you momentarily ‘stare’ at something (this is different from sustained ‘staring’ though) and usually last anywhere between 200-300 milliseconds, depending on the complexity of the visual task and the intention of the ‘looker’. You fixate longer on difficult words than on easier and more familiar ones. Fixations are when the visual scene is processed in great detail by the brain. During a fixation, the most sensitive part of the retina, the Fovea’, is aimed at the strongest area of interest, say a pedestrian about to cross the motorcyclists’ path and is a threat to him. But fixated vision is very narrow, barely 2-3 deg across and the brain tends to concentrate more on whatever lies within this narrow cone than outside it. So a biker who is in a habit of staring too long tends to ‘fixate’ more on what catches his eye and while he manages to gather more information about it than he probably needs, he allows his brain to neglect other possible threats in his field of vision.
The eyes produce a clear and wholesome picture of the scene ahead almost in the manner we stitch together sectional photos to build a panorama. Fixating too long causes the eye to lose its visual acuity meaning that the more you stare the less you see. So it is important to keep moving those eyes across the scene and allow the brain to build up a panoramic view thus giving you the entire visual scene in detail. As a thumb rule recommended by experienced motorcyclists and sports medicine experts, don’t stare at anything for longer than 2 seconds, especially when riding at high speeds. Keep those eyes moving to gather more and more situational awareness information. The point is to move those eyes and not the head. Moving the head blurs your field of vision and the eyes take time to fixate and the brain waits for the head to stop moving before it starts gathering information from the eyes.
Improving ‘Fixation’ efficiency: Play ball games or those involving moving objects like Badminton etc. even if you don’t play yourself, sit on the side-lines as close to the play area and track the path of the ball or shuttlecock by just moving your eyes while keeping your head as still as you can.
NOTE: Saccades are nature’s solution to overcome the drawbacks of a narrow field of ‘foveal’ vision. These quick movements allow the high resolution capable Fovea to rapidly scan the scene ahead and pick out important points to focus on thereby widening its effective field of vision. Also, saccades expose both the rods and the cones to changing light patterns, stimulating them, and so counteract the basic tendency of the human eye that begins to lose its grip on detailing if held still for even a few seconds.
Improving both the physical and visual reflex: Stand about 4 ft from a wall and throw a tennis ball at it. The ball bounces back quickly. Try and catch it with the other hand and throw it back as quickly as you can, again catching it with the hand other than the one you threw it with. As you get faster and better at 4ft, start getting closer to the wall. It gets progressively more difficult to track the ball from so up close and to catch it so fast reflexively. The point here is not to aim for perfection at catching every throw. Whatever effort you put into this exercise gives you direct benefits with improved concentration and better physical and visual reflexes.
Dynamic Visual Acuity
Simply explained, it deals with how quickly the eye focuses between up-close and distant objects. This is a saccade between up close and distant objects and the eye takes time to adjust its focal length. While this adjustment is taking place, the brain blanks out the real-time image and places a substitute last focused image as ‘sight’, for continuity. Now, the quicker the eye can adjust its focal lengths, the quicker you regain ‘real’ vision. If your eye takes long to focus when switching between the instrument panel and the horizon, then you are effectively riding blind while your eyes refocus.
Improving Dynamic visual Acuity: To improve this ability, extend your arm in front with the thumb vertical. Now focus on the thumb till you see a sharp image. Then quickly shift focus to a distant object, say a picture on the wall or even a far off building. Let its image become sharp and again get back to the thumb. Keep flicking rapidly between focused thumb and focused building/picture, willing yourself to be quicker and quicker at focusing. And feel the difference in your riding with a few days of practice.
The ‘Look but Not See ‘Syndrome
The fact that your eyes are fixated upon something is no assurance that you’re actually ‘seeing’ it. Remember the classic case of looking out of the train window and actually not being aware of the scene outside because you’re thinking of something else. So it is important not just to train your eyes to keep moving and looking but to also train your mind to concentrate fully on the task at hand and put to full use what the eyes perceive. Tiny ‘awareness triggers’ help you lock on mentally to your situation. These triggers can be a word of a couple of words you say to yourself when you become aware of your mind drifting away from the task at hand i.e. riding. Giving a commentary of the riding situation around you is also a great tool and quite a preferred one by advanced driving instructors.
The ‘Optical Flow and Motion Camouflage’
Physiologically though, the most salient and obvious feature in a visual scene while riding is movement. Dynamic or moving objects receive the most fixations, especially when the object involved threatens to collide with us. Usually, if the moving object moves against a static background, it is a lot easier to catch. And the ease further increases if it is moving laterally against your ‘optical flow’ i.e. say you’re moving northwards on your bike and an oncoming bike is headed south west or south east. That’s when it would be moving laterally against your optical flow. Also eyes perceive change in distance of a moving object through a change in its apparent size. So another vehicle moving directly towards you will just be detected by a change in its apparent size. For a motorcyclist riding at high speed, this can be a potential vision trap because the increase in apparent size is not actually proportional to the changing closing distance. That’s ‘motion camouflage’ and it is pretty rampant while the object moving in is far. The apparent size increases very slowly initially and then grows quickly rapidly as the closing distance decreases. So it might be too late for a corrective maneuver before a rider realizes that the approaching cyclist is too close for comfort. Also if something more dramatic happens to be closer to the biker (say that shapely girl walking her poodle demands a momentary fixation!) it will draw his attention from the oncoming threat all too easily. Of course, just turn the story around and you as a biker could be the ‘invisible’ one for that car or truck driver. Remember lateral motion helped and so a slight weave across the road will make you stand out easier from the background. And which is why riding with your headlights switched on, even in broad daylight, is so much safer. A moving object might still be missed but a BRIGHT moving object will not as the brightness in effect gives you a stronger visual presence, equivalent to being a larger object than you actually are.
Since a car driver will only sense the closing speed of an oncoming motorcycle by a change in its apparent size, the motorcyclist can make himself visible to the car driver from a further distance by adding a lateral motion to his movement. He does this by gently weaving his bike from one side to the other. This way, the car driver picks up the movement of the biker sooner than he would by a change in his apparent size.
There’s something called the ‘size-arrival effect’ that goes along similar lines. Smaller vehicles like motorcycles appear to approach you slower that they actually are. This can be dangerous for you as a motorcyclist as your closing distance with that car about to cross your path will be underestimated by its driver and he will probably pull out right into your path. Knowing that your ‘small size’ could lead the driver to committing that error gives you lead time to cover your brakes and probably slow down just a bit to match your actual arrival with his lower estimate.
This is where the importance of keeping those eyes moving and not fixating on anything for more than a couple of seconds becomes apparent. Changing sightlines keep your brain primed up for more incoming data and so it processes quicker. Also, the brain’s vision is a continuum of linked images that tell a story and not just a series of separate photos. So the linking to form a story becomes easier to do if the vision brings in information of as much of the entire environment or situation as it can. Which is only possible with a roving eye. All your ‘experience’ is based on linked sensory stories and become the classic stimulus – response action. For example, having seen a dog prick its ears and start moving diagonally towards a bike before starting to chase it make you remember the ‘story in images’ and just the picture of a dog pricking its ears on seeing you triggers a prediction within about what it will do next thus giving you precious advance warning.
Beware of the Visual Autopilot
The actions of riding need to become automatic and that’s exactly what we achieve by practicing them. Otherwise the brain would remain too busy helping you select the right gear and will not have spare processing capacity to handle other riding decisions like the need to swerve for that dog or brake for that car.
No wonder as a learner, even 40 kph is so exciting and overwhelming. Once the basic riding actions get ingrained in the sub-conscious, far higher speeds and complex traffic conditions can be handled with ease. But the point is not to let your riding decisions become automatic. And it is very easy to go into the ‘visual autopilot’ mode by just responding to regular visual clues on familiar routes. The actual riding conditions are unique each moment and need constant alert assessment. This complacency is too easy to get into on routes that you ride on very frequently vis a vis your daily commute. Almost everyone has been caught napping by a fresh new pothole on your office commute route that was dug up after you’d arrived home the previous night. Watch a mouse come out of its hole. Each time it does, even if the last exit was just a couple of minutes ago, it’ll be as alert and attentive as if it’s coming out the first time. Never trust the environment not to surprise you.
Lots of examples abound that support this autopilot mode. Take the example of teaching children and adults to look right – look left and again look right before crossing the road. This look right-look left – look right action could become purely mechanical and once performed, convinces the subconscious that the person has ‘seen’ all that was there to see. In fact, he might have completely missed an oncoming vehicle as he was thinking of something else while performing the seeing action (the look but not see syndrome). So watch out for that pedestrian who ‘look’ in the copybook fashion but fails to see you riding in. And of course so should you check yourself before riding across an intersection. Don’t just ‘see’ mechanically. See with your mind and consciousness in place.
Epilogue
The human eye is a tremendous creation and allied with the superbly capable brain, can show you sights you could never imagine could be seen. Imagine a camera that has a dynamic range as wide as 24 stops either side of proper exposure, that snaps pictures equivalent to 54 megapixels, can adjust focus in fractions of a second and can switch between high resolution stills and high definition videos within a literal blink of an eye and you’ll understand the enormity of the power our vision gives us. Know it better and learn to use it to its full advantage. Not only will you survive the roads but will do so with stupendously beautiful sights and memories captured over the years and decades of fun motorcycle riding.
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