Your Shifty Eyes

Some of the most captivating optical illusions are those that involve imaginary motion. Like the pattern of dots shown below, they appear to undulate hypnotically.

Figure 4-3. 

This illusion packs in two tricks. First, it uses contrasting colors that are perceived by different cells in the eye (without which the effect is much more subdued). Second, it varies the shading of different dots, placing the shadows above, below, and to the side of the various dots. (This trick is duplicated in hundreds of optical illusions.) However, neither of these details explains how a static image can fool your brain into seeing nauseating motion.

To really understand this illusion, you need to realize that your eye has a dirty secret—it's only able to see fine detail in a small fragment of its visual field. The pinpoint-sized part of your eye that sees sharply is called the fovea. If you look at a person an arm's length away, the fovea gives you a sharply detailed region that's about the size of a dime.

Figure 4-4. 

Your brain uses a crafty trick called saccades to compensate for this weakness. Saccades are quick, automatic eye movements. They're keenly important for reading books like this one, and they're equally indispensable for taking in the full detail of a visual scene. On average, your eye performs two or three saccades each second, ricocheting about your visual field without you even realizing it, each time capturing the fine detail of another tiny region. Inside your brain, these separate dime-sized pictures are pasted together to create a single, seamless whole.


If you're severely drunk, your saccades slow down, and you start to see the world the way your eye really perceives it—a patch of sharpness surrounded by a blurry field.

With this in mind, the drifting dots you saw earlier are easier to understand. As your eyes jump from one circle to the next, trying to stitch together the complete picture, your brain is confused by the alternate shading. After each saccade, the previously viewed dots aren't quite where your brain expects them to be, and so it assumes that they've shifted ever-so-slightly to the side. This creates the impression of motion.

You can will away this illusion to a certain extent by focusing intently on a small section of the pattern, and refusing to move your eyes. In this case, the center stops moving, but the sides continue to swell and heave like an unsettled sea.


Saccades don't just compensate for the blurriness of your vision outside the fovea. They also compensate for the unequal distribution of color sensitivity in your eye, and they mask your blind spot (which exists where the bundle of optic nerves exits your eye on the way to the brain).

One of the most famous illusions to take advantage of our shifty-eyed nature is the rotating snakes illusion, created by Akiyoshi Kitaoka, and shown in many alternate incarnations at The effect is strongest out of your peripheral vision.

Figure 4-5. 

Saccades are one of the many ways your eyes can deceive you. During a saccade, your brain compensates for the sudden movement by temporarily shutting down your visual input. This ensures that you don't see a dizzying blur streaking across your field of view. However, it also means you can miss sudden events that happen during a saccade (just as you can miss something important when you blink). Not only do the eyes lie, they also omit.

Keeping Focused

As you've seen, your brain keeps your gaze on the move, shifting your eyes to take in a full scene and moving your head to fix on important-seeming objects. This automatic movement creates a sticky problem. It means that it's much more difficult to focus on something that doesn't use the dynamics of sound, flashes of light, and bursts of movement to catch and hold your attention (for example, Gorillas in the Mist the book, rather than King Kong the movie).

This difference is particularly prominent in many business environments, where distractions abound and everything you're expected to do is monumentally boring. In this situation, focusing on a task like data entry is an epic battle between the paranoid parts of your brain, which are constantly on alert and waiting for the cues that indicate danger, and the conscious parts, which just want to get the job done so you can head off to the pub. So what can you do to win the war and keep your attention where you want it?

First, recognize what you can't change. Studies show that it's all but impossible for the brain to tune out distractions by sheer willpower. In other words, if people are given a task and told to ignore something unrelated, they can't. For example, experiments show that if you work on a computer monitor that has a background with a slowly moving starfield, the part of your brain that processes motion remains continuously active. Or, if you're shown pictures of famous faces while working on word problems, the face-recognition region of your brain lights up like a Christmas tree. The same is true when unimportant sound intrudes on your senses—whether it's a ringing telephone or a foul-mouthed coworker, it all gets processed. This is annoyingly inconvenient, but it makes sense. In our deep evolutionary past, tuning out a sound as loud as a hip-hop cellphone ringtone was likely to get you eaten.

With this in mind, here are a few good tips to keep your brain on task:

  • Don't try to fight distractions; eliminate them. Unplug your phone, turn off your radio, and close the door to your workroom. If you insist on doing your taxes in front of the television, you're asking for an audit. It's a skewed battle because the television has the help of your superior colliculus to reel you in.

  • Make boring tasks just a little bit harder. Studies show that the brain will start to tune out some superfluous information when it's wrestling with a challenge. (In the previously described studies, that means the parts of the brain that would ordinarily process the starfield's motion or the famous faces become less active when you're struggling with a tough task.) Obviously, this advice only lends itself to certain chores. For example, if you have to type a long list of names into a computer, you may be able to better keep your focus by racing against a clock, challenging yourself to enter names in larger batches, or playing a risqué rhyming game with each person's middle name.

  • Resist the distractions you can control. Although the automatic processing of your brain gives us all a certain degree of distractibility, studies suggest that roughly half of the distractions that derail us from tedious tasks are self-generated. Examples include snacking endlessly and hunting down rare action figures on eBay. In the corporate world, some businesses have found that a mandatory email-free day once a week boosts productivity, sometimes dramatically. Another email wrangling option: limit the number of times per day you check (in the morning, at lunch, and an hour before heading out, for example).

  • Don't worry about background noise. You should be able to tune out continual soft chatter, humming fans, and keyboard typing through a process known as adaptation, which is described later in this chapter (Ignoring Things). Essentially, the brain adjusts to a continuous stimulus, recognizing that it probably doesn't indicate an immediate threat.

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