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Explain xkcd: It's 'cause you're dumb.
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This well-known effect has of course been replicated in countless experiments.
Title text: This well-known effect has of course been replicated in countless experiments.


The BDLPSWDKS Effect in the title is an acronym for Bernoulli-Doppler-Leidenfrost-Peltzman-Sapir-Whorf-Dunning-Kruger-Stroop Effect, as explained by Ponytail in the comic. She stands in front of a slide that shows Cueball being subjected to this effect.

The effect mentioned appears to be a mashup of seven scientific principles (with nine scientists names included) from different scientific fields, with elements from each principle appearing in the resulting description of the effect:

The Leidenfrost effect refers to how liquid will produce an insulating vapor layer when in near contact with an extremely hot surface, causing it to hover over said surface. This is referenced by the firetruck lifting off on a layer of superheated gas.

Bernoulli's principle in fluid dynamics (also mentioned in 803: Airfoil) states that an increase in the speed of a fluid with certain properties occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. This is referenced by the lifted firetruck hurtling rather than just speeding.

The Doppler effect in physics refers to the change in a wave's frequency for an observer moving relative to its source. Sound from the oncoming firetruck increases in pitch. In tonal languages, changes in pitch change the meaning, making it harder for Cueball to understand the word screamed by the driver.

The Peltzman effect refers to how regulations intended to increase safety are ineffective or counterproductive. Red means stop and green means go, so yelling "red" would induce the (usually) counterproductive behavior of starting to walk more, rather than less.

The Sapir–Whorf hypothesis states that a person's world view and cognitive processes are affected by the structure of the language the person speaks. A language without a word for "firefighter" would conceivably not contain a word for "firetruck" either, thus avoiding the association with danger firetrucks have, slowing down Cueball's reaction.

The Dunning–Kruger effect refers to unskilled people mistakenly perceiving themselves as more skilled than they really are, while skilled people underestimate their own abilities. Obviously, if Cueball isn't fluent in the language, s/he'd take more time to process "green", as opposed to "red" in a well-understood language.

The Stroop effect refers to the phenomenon in which it is easier to name the color of the ink in which a word is written when the word refers to the same color as the ink than when the word refers to a different color. Firetrucks are red, this suggests that the driver shouting RED would get a faster response than the driver shouting GREEN.

Usually, for an effect to be considered real, the scientific method requires the effect to be replicated by different experimenters in different times and places. It is hard to imagine several scientists in different parts of the world creating the setup to replicate this effect; however the title text mentions (maybe sarcastically) it has been done countless times.

Furthermore, the opportunity of publishing this comic strip may (or may not) be related to the recently issued sequels of franchises such as `Mad Max` and `Carmageddon`, where it's not unusual to find heavy wheeled vehicles trampling pedestrians for fun, or simply because the drivers do not care.


[Ponytail stands next to a screen displaying a firetruck hurtling toward Cueball on what appears to be a layer of gas.]
Ponytail: The Bernoulli-Doppler-Leidenfrost-Peltzman-Sapir-Whorf-Dunning-Kruger-Stroop Effect states that if a speeding fire truck lifts off and hurtles towards you on a layer of superheated gas, you'll dive out of the way faster if the driver screams "red!" in a non-tonal language that has a word for "firefighter" than if they scream "green!" in a tonal language with no word for "firefighter" which you think you're fluent in but aren't.

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