A toddler, held in his mother’s arms, sees a puppy and points at it. “Puppy,” his mom says, training the boy to associate the word with the dog. “It’s a puppy.” The baby holds his gaze, transfixed, and keeps pointing. He points for a comically long time, for such a long time that he causes the mother and the dog walker to grin. The toddler is looking at just the puppy, only the puppy. His vision is singularly focused on it. All other objects are excluded from his sight. He only has eyes for puppy.
What happens in the brain when you focus your eyes on an object? Imagine you’re playing baseball, standing at the plate watching the pitcher as he winds up to throw a 100-mile-per-hour a fastball. You are singularly focused on spotting that ball the moment it leaves his hand, because you have to make a split-second decision about whether or not to swing.
There’s a lot going on in that split second. Light enters your cornea and gets focused by the lens to the back of the eye. There it gets picked up by the retina where photoreceptor cells convert it into electrical signals. They travel through the optic nerve to your brain, passing through several processing stages including the optic chiasm, the thalamus, and the primary visual cortex near the back of your skull. The visual cortex analyses the signals for visual features such as contrast, motion, and depth. From there the signals pass to the higher-level brain regions of the inferotemporal cortex where they undergo a recognition process — “This is a swingable pitch” or, “This is not a swingable pitch” — relying on stored knowledge from prior batting experiences. Then there’s the decision-making process, to swing or not to swing, which plays out in various brain regions including the prefrontal cortex and other motor-control areas.
Generally, the transmission of electrical signals and basic feature analysis that characterize the initial stages of visual processing occur rapidly, within tens to hundreds of milliseconds. Let’s face it, in the scale of human perception, such speeds are basically instantaneous. No time at all. However, higher-level functions involving recognition, cognitive processing, and decision-making typically take longer. The best major-league batters may process the information in hundreds of milliseconds, whereas the average beer-drinking baseball fan may have no clue if it’s a swingable pitch or not until well after the ball is in the catcher’s mit.
When you focus on an object, you prioritize it at the expense of other objects in your field of vision. The puppy. The baseball. The beer. Whatever the object of focus, it receives the majority of your attention. The region of your visual field corresponding to the focal point is the fovea. It is centered in a tiny area of the retina and contains a dense cluster of photoreceptor cells responsible for discerning detail. Foveal vision attempts to maximize visual acuity of the focal object.
Meanwhile, other visual stimuli that fall outside the immediate vicinity of the fovea are processed in a more coarse, less detailed manner. They are picked up by our parafoveal vision, also called peripheral vision. They receive less attention or they may be excluded from consciousness altogether. We described this phenomenon in the recent post, “Did You Spot the Gorilla?”
The toddler sees the puppy, not the leash, the dog walker, nor the sidewalk. The batter sees the ball, not the pitcher, nor the baseball field, nor the fans in the bleachers. This area of focus is called the visual attentional spotlight. We humans have developed our attentional spotlight through millions of years of evolution dating back to times when spotting a predator or not spotting a predator meant the difference between survival and extinction.
The point is, we focus on the things that are important, at the exclusion of virtually everything else. This makes us good at spotting something once we know what to look for, a skill developed over millions of years of evolution. If our hominid ancestors happened upon a berry patch, they would think, “Oh look, here are some delicious berries on this bush,” and then they would focus their vision on other branches of the bush and nearby bushes to find every delicious berry.
In this type of situation, you form a mental picture of the berry in your mind, and then your eyes scan your surroundings for other objects that resemble that berry. If the berry is red, your eyes dart to other objects that are red. If the berry is fuzzy, your eyes scan for other fuzzy surfaces.
But just as the mental picture in your mind can help you to identify things that are familiar, it can also prevent you from spotting things if you don’t know what they look like, or if they look like something other than the picture in your mind.
Let’s say you misplaced your car key, and you’re in a hurry to find it. You don’t know where you left it but, good news, it should be easy to find because it’s attached to a hoop keychain that’s as large as a tennis ball. You have a mental picture of that keychain in your mind. You scan the area for a tennis ball-sized hoop. Where is it? Your eye goes to everything that’s round like the hoop. Where is that damn keychain? You go from room to room. You start looking in places that are less and less likely, because you didn’t find it in the places that were more likely. You know it must be in the house because you used it to lock the car door when you got home. Eventually, you have to give up and call a friend to give you a lift, otherwise you’ll be late. You spend the rest of the night wondering where that key could be hiding. It’s attached to a big hoop! How could it be lost?!
The next morning you wake up still thinking about the hoop key chain. As you are making coffee, you look across the room and spot it immediately on the low coffee table. The problem was, the hoop was not laying down flat but rather standing on its edge. Therefore, when you were racing around the house the night before and you stood over it looking down at the coffee table, the object appeared oblong, not hoop-shaped, as expected. Your eyes had glanced at it, but because the object didn’t match the shape that you had in your mind’s eye, you did not recognize it.
Nature knows this all too well. The Orchid Mantis resembles an orchid flower. Walking-Stick insects imitate twigs. Vine Snakes look like vines. Leaf-Tailed Geckos are practically invisible when motionless in foliage. When would-be predators approach these creatures, they pass over them because they don’t look like things that look like lunch. Fly Orchids develop flowers that look like female flies, attracting male flies and aiding pollination. The male fly buzzes away in frustration mumbling, “I gotta get my bug eyes checked – I coulda sworn there were some ladies on that flower!”
You can develop techniques for noticing things in your parafoveal vision. There are simple exercises designed to enhance peripheral-vision awareness. Anyone can do them. Just sit and softly focus on an object in front of you. While keeping your focus on the object, relax your vision and try to expand your awareness of the things that surround the object. You’ll notice that as you mindfully expand your attentional spotlight, the vividness of the initial object decreases but you can take in a wider spectrum of sights.
Go ahead and try it now to see how that works.
It takes concentration to maintain this broad view, since it is not the way you normally use your eyes. What you’ll notice is that as you intentionally de-focus your vision, your mind tends to move from area to area surrounding the initial object. In this process, you’re not exactly seeing each objects but, rather, taking in a broad field of vision, establishing an awareness of the surrounding objects in a softer, more diffuse form of vision.
Some flashlights have a similar feature that allows the beam to be focused and concentrated or broad and diffuse. Your vision can operate in the same way. You can concentrate your visual focus in a tight area, as you usually do, or you can spread out your visual field in a less focused manner. With some practice, you can shift back and forth between a tight, vivid focus and a diffuse view of a broader plane.
The point is, your eyes serve you well as efficient task masters, locating the things around you that are important. But this efficiency can also leave you blind to certain things that are right in front of you. Remember, foveal vision attempts to maximize visual acuity of the focal object. If you choose to consciously de-focus your eyes to take in a different perspective, you may give yourself the opportunity to notice things that you wouldn’t notice otherwise.