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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: I'm Lauren Vogelbaum, and today's question is why our stop

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Speaker 1: signs read? Why not green or purple? Why not mango

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Speaker 1: tango or tickle me pink. In the early days of

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Speaker 1: motor vehicles, the rules of the road were, let's say,

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Speaker 1: they were really more what you'd call guidelines than actual rules.

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Speaker 1: Believe it or not, the first stop signs in America

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Speaker 1: were not put in place until nineteen fifteen. According to

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Speaker 1: historical estimates by the Federal Highway Administration. In nineteen fifteen,

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Speaker 1: they were already almost two point five million cars driving

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Speaker 1: on US roads when those much needed first stop signs

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Speaker 1: finally did show up. It happened in the motor capital

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Speaker 1: of Detroit, Michigan, and they were not the red octagons

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Speaker 1: that we know and love today, but white squares with

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Speaker 1: black letters. Now. Traffic sign codes throughout the twentieth century

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Speaker 1: have recommended several different variations on the basic design. For example,

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Speaker 1: in ninety five, United States got its first official manual

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Speaker 1: on Uniform Traffic Controlled Devices, which said stop signs should

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Speaker 1: be a yellow octagon with black or red lettering. It

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Speaker 1: wasn't until the nineteen fifty four revision of this edition

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Speaker 1: of the manual that the red octagon with white letters

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Speaker 1: became the law of the land. According to that document,

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Speaker 1: the red color is consistent with the accepted use of

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Speaker 1: a red light as a stop signal and of the

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Speaker 1: color red as a special warning of danger. Furthermore, they

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Speaker 1: explained that the original decision to use yellow instead of

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Speaker 1: red was because red pigments were more likely to fade

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Speaker 1: over time with exposure to the elements. However, by the

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Speaker 1: nineteen fifties, the state of California had solved the problem

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Speaker 1: by using porcelain enamel to protect their precious red signs,

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Speaker 1: and higher durability red paints were becoming more widely available,

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Speaker 1: and like that, red became the new yellow. But there's

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Speaker 1: a question that goes deeper than uniform traffic signaling protocol.

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Speaker 1: Why red? Is there any reason to think a red

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Speaker 1: stop sign would work better than any other color at

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Speaker 1: getting drivers to stop zooming straight through intersections at eighty

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Speaker 1: eight miles per hour. One fairly obvious answer is that

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Speaker 1: red is not as likely to blend in with the

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Speaker 1: landscape as some other colors. This explains why the Highway

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Speaker 1: Administration has repeatedly rejected our proposal for a green and

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Speaker 1: brown camouflage pattern to stop sign. Another important point is that,

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Speaker 1: like the aforementioned Manuel says, a red is a color

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Speaker 1: we consistently use to identify warnings and peril, think about

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Speaker 1: the wrong way sign and the do not enter sign.

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Speaker 1: Having consistent color coding helps drivers learn to identify specific

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Speaker 1: colors with specific messages. So even if you only catch

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Speaker 1: the hint of a red sign out of the corner

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Speaker 1: of your eye, you're more likely to react with caution

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Speaker 1: the way you've been taught. There are also some behavioral

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Speaker 1: research findings that might point to the inherent power of

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Speaker 1: the color red to command our obedience. For example, a

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Speaker 1: study published in Psychological Science found that male reesist monkeys

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Speaker 1: under test conditions were less likely to steal apple slices

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Speaker 1: from human experience mentors who were dressed in red. The

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Speaker 1: monkeys didn't seem to care about the gender of the

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Speaker 1: human experimenter, and we're not deterred by green or blue clothing,

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Speaker 1: but a red hat and T shirt were enough to

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Speaker 1: make the monkeys cautious about swiping that fruit. Now, it's

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Speaker 1: important not to read too much into that result. The

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Speaker 1: study was done on monkeys, who could be reacting to

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Speaker 1: red for all kinds of reasons, but it at least

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Speaker 1: suggests the possibility that there is a primate instinct to

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Speaker 1: associate red with dominance or authority, and if humans share

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Speaker 1: this hypothetical primate instinct, the difference between a red stop

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Speaker 1: sign and a yellow stop sign might be the difference

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Speaker 1: between stop and the name of the law. And hey, hey,

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Speaker 1: hey guys, it might be nice if you came to

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Speaker 1: a halter you know, turned off your nitro boosters. Today's

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Speaker 1: episode was written by Joe McCormick and produced by Tyler Clang.

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Speaker 1: For more on this and other arresting topics, visit our

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Speaker 1: home planet, how stuff Works dot com.