Big World, Little Brain

Art by Paul Kim. Copyright Rebecca Schwarzlose

How does your brain—an organ smaller than a soccer ball—represent the big, wide world of sensations, events, and meaning unfolding all around you? 

Your experience of the world feels so seamless and boundless that you may never have thought to ask this question. But once asked, the question demands an answer. Or, in this case, it demands three answers. Because it is only thanks to three solutions that you can perceive your world at all. And it is these solutions, in turn, that determine exactly how you experience your world.

You Miss More Than You Think

The first and simplest solution is that your brain doesn’t represent everything taking place around you. Not even close. You perceive only a small fraction of the energy and information buzzing all around you.

Much of that buzzing information goes unseen and unfelt because your body lacks the capacity to detect it. Whereas birds can see ultraviolet light, snakes can see infrared light, insects can see the polarization of light, mice can hear ultrasonic frequencies, and electric fishes can detect faint electric signals with their skin, you can do none of these things because your eyes, skin, and ears lack the cellular machinery that would allow you to detect them.

Although having infrared vision would be a great party trick for you or me, it is vital for snakes that need to hunt their prey in the dark. Every creature’s body is mostly blind and insensate, only detecting those faint signals from the environment that it needs to survive.

But being mostly blind to the goings-on around you is only part of the solution. That’s because you can only comprehend the thrum of information you do receive from your eyes, skin, ears, nose, and tongue if it is processed by your brain. This processing depends on the activity of brain cells called neurons and the connections between them. Brains with more of these interconnected neurons can process more information, but they are also heavier and require more energy. As a result, perceiving any feature of one’s world comes with steep costs: a larger, heavier head to house one’s brain and a larger appetite to sustain it.

Your Brain Is Full of Maps

This brings us to the second grand solution that makes perception possible. Creatures on earth, including humans, eke more abilities out of their brains by organizing neurons into literal maps. These maps allow creatures to pack more neurons into a brain while keeping the costly connections between them as short as possible.

Your different brain maps represent different features of your world: information about light detected with your eyes, information about sound detected with the cochleae in your ears, pressure detected with your skin, locations in space around your body, and so much more. Thanks to maps, your brain can house five senses rather than just one or two, all while keeping your hat size small and your appetite manageable. 

Yet brain maps alone cannot solve the problem of perceiving a big world with one measly brain. There is still too much detailed information reverberating in the world around us and only so much energy and headspace to go around. As a result, your brain maps cannot faithfully represent all the information striking the surfaces of your skin, the backs of your eyeballs, and the deep recesses of your ears.

Your Maps and Your Perceptions Are Warped

This brings us to the third grand solution: Your brain maps are warped, preserving some details while sacrificing others

Much like Manhattan real estate, territory in the brain is both finite and expensive. Brains evolve and develop to make the most of that modest terrain. Your brain maps are distorted to save energy and space. And these distortions, in turn, distort how you perceive your world.

Consider your sense of sight. You can see far more detail at your center of gaze, or where you are looking at any given moment, than “out of the corner of your eye.” For an illustration, just try reading these words without looking right at them.

Ideally, you would be able to see things equally well out of the corner of your eye as you do at your center of gaze. But you need more neurons, and more connections between those neurons, to represent fine details. In order to see equally well in your visual periphery as you do at your center of gaze, the visual maps in your brain would have to be thirteen times larger. If this change sounds innocuous, think again. It would make your visual brain maps alone too large to fit inside your skull. And that would leave no room for the brain maps you rely upon to hear, feel, and move.

To avoid such catastrophic outcomes, brain maps devote most of their estates to representing detailed information from “sweet spots” for perception, at the expense of practically everything else. 

When it comes to touch, your sweet spots are your fingertips. You can measure your ability to detect fine detail by asking someone to apply two points of pressure against your skin and testing how far apart they need to be for you to detect that they are two points rather than one. With your index finger, you can distinguish between two pressures a mere millimeter apart—a true feat of detailed tactile perception. That distance must be about seventy times greater—roughly the width of a woman’s hand—for you to distinguish between them on your back.

Oddly enough, your ability to perceive crucially depends on all that you don’t perceive. Thanks to our limited senses and distorted brain maps, you can experience and interact with your world… and do it all with a brain that’s smaller than a breadbox.

This post first appeared on Psychology Today

Brainscapes Coming Soon

Figure from Brainscapes showing the layout of a brain map that represents touch on the body’s surfaces. Illustration by Paul Kim.

My book, Brainscapes, will be released this coming Tuesday and I could not be more excited to share it with the world. Brainscapes tells the story of brain maps–actual maps of space, action, and perception written into the surfaces of your brain. These maps represent the world around you, dictating what you perceive and shaping how you move, imagine, remember, and dream.

I will be posting more updates about Brainscapes after its release and as more reviews and associated interviews are posted. For now, I want to share a few links to early reviews of Brainscapes, as well as information about two virtual launch events for the book organized with indie book stores. I hope you will join me for one of the events and learn about the book and your own brainscapes.

Here are the upcoming events. . . .

Brainscapes Event, The Novel Neighbor, June 16, 7:00-8:00 PM Central

Brainscapes Event, Seminary Co-op, June 29, 6:00-7:00 PM Central

Here is a recent interview about the book for the Smart People Podcast

And here are a few early reviews of the book . . .

“Neuroscientist Schwarzlose debuts with a fascinating deep-dive into the “remarkable maps” in the human brain. . . . This is deeply enjoyable and thoroughly researched—science-minded readers should take note.”
Publishers Weekly starred review

“The scope of the book is staggering, as is the potential of technology’s role in decoding minds, and yet Schwarzlose successfully and enthusiastically relays the research in relevant, understandable, and absorbing language.”—Kirkus

“This potentially dense and impenetrable subject is illuminated and rendered comprehensible in Schwarzlose’s skilled hands. A fascinating in-depth exploration of the maps contained within our brains. Recommended for science lovers.”Library Journal

The Act of Falling


Facing the future with another hand in yours. Photograph by Stephanie Bassos.


I recently had the honor and pleasure of reading something at the wedding of two wonderful people: my dear brother-in-law Arvin and his remarkable (now) wife Erica. It was a beautiful and very special ceremony.

My reading was a . . . something (essay? prose poem?) that I wrote for the occasion. In writing it, I was inspired by the couple and their loving ease and flexibility, both together and with extended family. My other inspiration was a cool scientific paper describing the End of History Illusion.

And so, with love and congratulations to happy couple, I am posting the something that they inspired me to write.

Here is a psychological fact: we realize how much we have changed in the past, but we are blind to all of the changing we have left to do. This is as true at 75 as it is at 17. We cannot comprehend that we are each perpetually becoming someone new. It is hard to believe, hard to accept. You will be many different people in the course of a single life.

But what happens when we meet someone and fall in love? We know ourselves and each other right now, at this moment. And we are ready to take this moment forward to forever. But there is a catch. You are not done becoming you and I am not done becoming me. Today is a still-frame but we are movies – unfolding and emerging over time. That is why marriage is a risk, a leap of faith, an act of courage. It is an investment whose return you cannot guarantee.

But sometimes one person finds another, and they fit. Do not call their relationship rock-solid; it is nothing so rigid as that. It is two people who bend and flex, who together weave a future out of cloth and not stone, out of mutual respect and affection, not expectations of permanence or perfection.

Sometimes two people decide to take that leap and to invest in each other, to change and grow together and to commit to honesty and love. Just as a parent can hold a newborn and love all of the people that child might one day grow to be, two people can commit to the certainty of uncertainty, to loving what they have not yet become.

People say that marriage is a balancing act, but it is nothing so contained or so ordinary. It is the act of falling, but of choosing to fall together. It is choosing to create and adapt and sometimes falter and fight because you will have the remarkable privilege of evolving together and of loving the many different people that you will both turn out to be. It is a choice to face an unknown future with another hand in yours. To grow up, or grow out, or grow old – but to grow, and to always keep growing together.

Podcast Interview on Writing Review Articles (Bonus: Grandmother Orcas)


Photo by Robert Pittman, public domain

I was recently interviewed for the Cell Press Podcast about a post I wrote for CrossTalk, the Cell Press blog. The post was a how-to for scientists who want to write a review article that people will actually read.

Awesomely, people actually read the post too. It quickly became one of the most read posts of 2016, even though it appeared in mid-December. I was delighted by the enthusiastic response and equally delighted to discuss these ideas further for the podcast.

My interview comes at 17:10 in the podcast. Find it after post-menopausal killer whales and the vaginal microbiome! You can also listen here:

Be the Sucker Who Waits to Cross


You’ve seen him before: the poor soul who doesn’t cross the street on a Don’t Walk signal, even when there isn’t a car in sight. Even while other pedestrians are streaming past him, crossing the street and continuing along their merry way. Bottom line: you should try to become that guy.

Think of it as a late New Years resolution. Most resolutions are lofty and hard to carry out. Chances are good that if you made a resolution for 2017, you have already broken it. But waiting for the Walk signal is a resolution that you can keep for life. It would be an easy win, and one with a small but increasing likelihood of saving your life – or someone else’s.

First, a few facts. Pedestrian fatalities and injuries in the U.S. are on the rise. A pedestrian was injured from a traffic accident every eight minutes, on average, in the United States in 2014. One died every two hours. The vast majority of these deaths, more than 70 percent, take place in urban areas. Over half of those who die in traffic accidents in New York City aren’t in a car – they are on foot.

Few among us would advocate jaywalking. Waiting for the signal to cross is great in principle, but in reality we have compelling reasons to disobey that lighted hand. The most obvious is that we are in a hurry. There are a million tasks waiting for us at work, with a million more waiting for us when we get back home.

Unfortunately, our long to-do lists are precisely the problem. In modern life, distraction is the norm – even without handheld distractions. The human mind is simply prone to wander. A study suggests that we may spend as much as half of our waking hours thinking about something other than what we are actually doing. In other words, those million tasks aren’t just waiting for us at work; they travel with us (and distract us) wherever we go. If you’re like me, you get from place to place on autopilot. That’s fine if you’re a plane, but less than ideal if you’re a pedestrian.

Distraction isn’t our only enemy. Our social nature is also to blame. We are descended from a long line of creatures who follow each other automatically. Think of our living relatives in the animal world: herds of wildebeest, swarms of ants, schools of fish, or flying bird formations. Like them, we use cues from the creatures around us to determine how and where we move. In the case of crossing a street, when one pedestrian begins to cross the street, others tend to follow – often without noticing the traffic circumstances until they are standing in the street.

I have been the trailing wildebeest, blindly following the herd, more than once in my life. Nothing rivals the sunny day when a friend and I were riding home from high school on our bicycles and stopped behind a classmate on the sidewalk. We chatted while waiting for the Walk signal and, when our classmate rode out into the intersection, we instinctively followed him. Perhaps on some level we assumed that he was crossing with the light, but he was not someone we would consciously have trusted with our lunches, much less our lives. All the same, my friend and I looked up to find a car barreling towards us. When the car screeched to a stop just shy of my left caIf, I stared through the windshield, feeling as if I was inside the car with the driver and her two young children.


Talk (but Don’t Walk) to the Hand. Photo by DMangus CC BY-NC-ND 2.0

Beyond the social pull of fellow travelers, we are also at the mercy of our own internal states. Extreme moods or physical discomfort can distract us from our surroundings, but there is also the elephant in the proverbial intersection: alcohol. Although there have been campaigns against driving under the influence, we don’t talk about walking under the influence. Yet in an estimated 34% of U.S. pedestrian deaths in 2014, the pedestrian had a blood alcohol concentration at or above the legal limit for driving under the influence. If you have a few drinks and make the very good decision to walk rather than to drive home, you still face risks from your inattention and sluggish reaction times.

So how do we keep from following others or meandering into the street when we are on autopilot, distracted, or impaired? Being aware of one’s surroundings is always best, but you also need a backup plan. You can make one by building a new habit. Wait at all signaled intersections until you see the Walk signal – even if there isn’t a car to be found. Wait that extra minute for the signal every time, just as you would if you were a car waiting at a red light. If waiting for the signal becomes a habit, then you will default to it, even when you are on autopilot.

Now consider a few benefits of this habit. First, if you cross for a Walk signal, then you are crossing at the intersection. This alone greatly reduces your risk of being struck by a car. In 2014, 71% of US pedestrian deaths occurred outside of an intersection. And as a moral bonus, creating this habit for yourself can also protect others. If you don’t cross against the light, your distracted fellow walkers won’t follow you out into traffic. That particularly benefits children and the elderly, who may require more time to cross the street.

Over the past two years, I have been cultivating this habit. I have been that sucker who waits for the Walk signal, even when there isn’t a car to be seen. I had the idea of writing this post on the walk to work one day. I arrived at my office with an outline of it in my head – but no recollection of actually treading the sidewalks and crossing the streets along the way.

Still, I know one thing: I obeyed that lighted hand.

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