Tag: senses

For Stealthy Electric Cars, Auditory Illusions Could Save Lives

By Mark Changizi | September 13, 2012 9:30 am

Mark Changizi is an evolutionary neurobiologist and director of human cognition at 2AI Labs. He is the author of The Brain from 25000 FeetThe Vision Revolution, and his newest book, Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man.”


The silent purr of an electric car is a selling point over the vroom of a gasoline engine, but it comes with an undesirable side effect: An electric car can pounce on unsuspecting passerbys like a puma on prey. In fact, the NHTSA found that hybrid electric cars are disproportionately dangerous to pedestrians. To deal with this problem, it has been proposed that sound be added to hybrid and electric vehicles, whether it be bird-songs or recordings of someone making “vroom vroom” sounds.

In this light, I wondered whether it might be possible to add “smart sound” to these dangerously quiet cars destined to rule the road in the near future. The solution, I realized, might come from faster-than-light-speed objects on the moon. I’ll get to this crazy-sounding part in a bit.

The Melody of Movement

In setting out to solve this problem, I reasoned that when electric cars are moving very fast they make enough sound to be heard due to the rumblings of the car parts. It’s when they’re moving at lower speeds that they’re most perilous, because at these speeds they’re most silent. Therefore, if electric cars are to be fitted with some sound, it should be designed to work even at lower speeds—or, especially at lower speeds.

Next question was, What sort of sound do we want on slowish, stealthy electric cars? To answer this, it helps to grasp the sorts of cues your auditory system uses for detecting the movement of objects in your midst.

The most obvious auditory cue is that nearer objects are louder, and so when you hear a moving object rising in loudness, you know it’s getting closer.

But that’s not the most important auditory cue. To illustrate why, imagine walking along a curb with traffic approaching and passing you from behind. The important observation here is that when this happens you aren’t in the least worried. Even without seeing the car, you know it’s merely passing you despite the massive crescendo in its sound. Why?

Doppler shift illustration
The Doppler shift changes the observed pitch of the siren as the car moves.

You know the car isn’t going to hit you because of its pitch. Due to the Doppler shift, this car has a falling pitch, and this falling pitch contour tells your brain unambiguously that, although the car is going to get arm-reachably close, it is going to pass you rather than collide with you. If it were going to collide with you, its pitch would be high and constant—that’s the signature of a looming collision.

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CATEGORIZED UNDER: Mind & Brain, Technology, Top Posts

Turning Japanese, or, How to Change Your Self’s Ethnicity in Just 1 Week

By Mark Changizi | May 25, 2012 8:45 am

Mark Changizi is an evolutionary neurobiologist and director of human cognition at 2AI Labs. He is the author of The Brain from 25000 FeetThe Vision Revolution, and his newest book, Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man.”


Tom Stafford, co-author of the excellent book Mind Hacks, recently wrote a piece for the BBC about one of the most fundamental principles in the brain’s arsenal. This principle is so important that it ought to have a super-excitingly electrifying name; alas, it’s misleadingly boring. The principle is “adaptation,” or otherwise called “tuning out” or “getting used to it.” In an effort to help further communicate the sorts of powers adaptation gives us, it struck me to relate a remarkable “adaptation encounter” I recently had.

In 2011 I had the pleasure of visiting Japan for the first time. In addition to fascinating neuroscience, priceless culture, wonderful food, and world-class skiing, during my week there I had the mind-blowing experience of…turning Japanese.

You don’t think it’s possible for a white person to turn Japanese? Well, you can…perceptually. In fact, although it is I who had turned Japanese during my stay, from my first-person perspective it seemed as if every Japanese person had turned Caucasian!

As Twilight Zone-ish as this may sound, this sort of transformation is well-known and commonplace. What made it so intriguing for me was the extent to which I was, by virtue of my research proclivities, consciously aware of what usually flies below radar.

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CATEGORIZED UNDER: Mind & Brain, Top Posts
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