Tuesday, July 15, 2008

How the Brain Works and Bicycle Visibility

Last week I read an interesting essay which made me think about visibility out on the road. Some excerpts for those who don't want to read the whole article (interesting article but long).
A new scientific understanding of perception has emerged in the past few decades, and it has overturned classical, centuries-long beliefs about how our brains work—though it has apparently not penetrated the medical world yet. The old understanding of perception is what neuroscientists call “the naïve view,” and it is the view that most people, in or out of medicine, still have. We’re inclined to think that people normally perceive things in the world directly . .

Our assumption had been that the sensory data we receive from our eyes, ears, nose, fingers, and so on contain all the information that we need for perception, and that perception must work something like a radio. It’s hard to conceive that a Boston Symphony Orchestra concert is in a radio wave. But it is. So you might think that it’s the same with the signals we receive—that if you hooked up someone’s nerves to a monitor you could watch what the person is experiencing as if it were a television show. . .

The images in our mind are extraordinarily rich. We can tell if something is liquid or solid, heavy or light, dead or alive. But the information we work from is poor—a distorted, two-dimensional transmission with entire spots missing. So the mind fills in most of the picture. You can get a sense of this from brain-anatomy studies. If visual sensations were primarily received rather than constructed by the brain, you’d expect that most of the fibres going to the brain’s primary visual cortex would come from the retina. Instead, scientists have found that only twenty per cent do; eighty per cent come downward from regions of the brain governing functions like memory. . .

The account of perception that’s starting to emerge is what we might call the “brain’s best guess” theory of perception: perception is the brain’s best guess about what is happening in the outside world. The mind integrates scattered, weak, rudimentary signals from a variety of sensory channels, information from past experiences, and hard-wired processes, and produces a sensory experience full of brain-provided color, sound, texture, and meaning. . .

All of this made me think what many of us have probably intuited--drivers literally don't see us because they don't expect us to be there. They've been conditioned to look for cars and only cars, so that's what they see. And it also suggests why they get ticked off when they see you later rather than sooner. Their own perception has been indicted found faulty. Every driver knows they shouldn't overlook somebody on the road, but people like to blame others rather than themselves, so "How did I not see that cyclist? I should pay more attention." becomes "That damn cyclist, what are they doing on the road!"

This new understanding of perception also goes a long way to explain the safety in numbers effect. Scientists who first studied serious injury among cyclists went into the research thinking that where more people biked, injuries would rise because cyclists would feel more secure and thus be less careful. They found the opposite was true, the more cyclists that were in a given area, the less likely they were to be injured.

It also suggests that for people who live in an area without a lot of cyclists on the road visibility should be thought as shocking the perceptions of drivers. Being visible to someone who is looking isn't enough, because the "brain's best guess" is that you aren't there. I'm not a big fan of bike specific clothing, but the hi-vis green and orange shirts that highway workers wear seem like a real good idea. I presently wear red or (regular) green when I ride anywhere outside of downtown where the traffic is going over 30mph, but I'd like to get some cotton hi-vis shirts.

Here are several pictures of the setup I run when I leave the cozy confines of my neighborhood (traffic downtown is pretty good since their are lots of cyclists and pedestrians).

The light on the left is a Planet Bike Superflash, which is very bright, familiar to a lot of people, and the only light I use I night downtown. The light on the right is a Dinotte Taillight (I sell both). The triangle is a reflective hi-vis green triangle with a hi-vis orange center. My family has dubbed the Dinotte the "shock and awe" light. It has a very arresting BAM-BAM-BAM-pause-BAM-BAM-BAM flashing pattern and you literally cannot look directly at it without intensely hurting your eyes. It is visible even in broad daylight. Cars pass at very noticeably slower speeds and greater distances with this light. I could be wrong, but I'm convinced that the car that hit me from behind in Dallas wouldn't have hit me had I had this ridiculously bright light (I was using two Planet Bike BRT-7's at night. Driver wasn't drunk, he just "spaced out." He was about as scared as I was and actually raced me to the hospital himself.)

"Daylight" shot--hi vis triangle doesn't show up as well in the photograph under florescent lights

Low-light Shot without rear illumination

Low-light Short with rear illumination

Shot from the front to give some perspective of just how much light the Dinotte puts out. There it still light coming into the shop from the front window (it was dusk outside) or the light would show even more contrast

Payin' the bills content: Planet Bike Superflash lights are $24. Dinotte Taillights are $170 for the AA version and $230 for the Lithium Ion. Both include batteries, charger, and seatpost mount adapters. (I can tell you how to mount it in other spots if the seatpost isn't a good location for you--mine is attached to a seatstay rack boss. Shipping is free the Dinotte lights and all small part orders over $150 (no wheels, rims, bikes, or frames). I'm not much for "If it saves you one trip for the hospital its worth it" pitches. My take is these expensive lights are worth it for the stress they save you while riding. They buy you more room out there, which makes riding a lot more pleasurable. They're American made and have a two-year warranty. I offer a thirty day trial period for these lights. If you're not satisfied, just return the light--no matter how much you've used it--within thirty days and you'll get a full refund. No one has ever taken me up on that one.


jerry said...

Try AlertShirt.com for the best commuting shirts I have found.

Great stuff and great people.

I'm just a VERY satisfied customer.


David said...

Great post. Thanks for spotting the essay. This is a great example of incredibly complex situations that we're really only beginning to understand scientifically. This will help explain to skeptical riders and motorists why "Bicyclists fare best when..."

Mike said...

Where did you get the triangle light. I almost got killed this morning by a car that did not see me. I need something like that. Thanks

Longleaf Bicycles said...

The triangle is not a light. It is reflective and hi-vis green with a hi-vis orange center. I stock the them. They're $10 each.

Todd Guess said...

Taillights are important, sure, but overtaking collisions only represent 4% of all bike-car collisions. By all means, get a good taillight, but never at the expense of a good headlight.

Ben said...

This reminds me of something mentioned by Prof. Jeremy Wolfe, of MIT. He calls it the "attention bottleneck." Meaning there is only so much that the brain can take in, and so the brain filters out what it deems un-important, and averages in other parts that it assumes is the same (try putting an "x" on a white sheet of paper, then look 3" to the left, wierd huh?). This means that the bicyclist gets "averaged out" in the bottleneck of the brain.

It's an interesting lecture, and he's got many more here:


It is essentially is the same thing as the article, just spoken by a cool northerner.

Bryan said...

I’ve been studying human perception since I was a teenager. Not by going to school or anything cliché like that, but by experimenting on my fellow man. It’s true: people just don’t see what they’re not expecting to see. My work has shown that this varies strongly depending on the culture of the subject. The good news is that the Japanese are almost as perceptive as children. The bad news is that the least perceptive would seem to be the garden variety middle class westerner.

That, to me, is the best argument for Vehicular Cycling; drivers are scanning for other cars, and on a good day they might think to check for a pedestrian or two at a major intersection. But that’s it. If you’re on the sidewalk, do you really think they’re gonna check there to see if a misplaced Buick is charging toward them from somebody’s front porch? No. They’re not. So if waking up on the right side of the dirt is important to you, you’ll put that bicycle exactly where the person trying to kill you, err, I mean driver, is directing his attention. It just so happens that the only place he’s directing his attention is the area where he has a reasonable expectation of finding moving cars.

Yes, you may annoy somebody. You might even cause them to have to slow down or, god forbid, operate the steering wheel ever so slightly. But the good news is that there is an excellent chance that, with lots of expensive therapy and some recreational drug use, they’ll probably manage to get over it some day.