Main Page

Explain xkcd: It's 'cause you're dumb.
(Difference between revisions)
Jump to: navigation, search
(Latest comic)
(Latest comic: add discussion)
Line 14: Line 14:
<br clear="right">
<br clear="right">

Revision as of 20:22, 9 August 2012

Welcome to the explain xkcd wiki! We already have Expression error: Unrecognised punctuation character ",". comic explanations!

(But there are still Expression error: Unrecognised punctuation character ",". to go. Come and add yours!)

Latest comic

Go to this comic

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:

  • 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 firetruck lifting off and hurtling.
  • 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.
    • This is referenced by Cueball reacting faster if the shouting is in a non-tonal language than a tonal language. In tonal languages, changes in pitch change the meaning, thus tonal langauges may suffer more from Doppler distortion than non-tonal ones.
  • 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.
  • The Peltzman effect refers to how regulations intended to increase safety are ineffective or counterproductive because people, feeling safer, will engage in riskier behaviours.
    • This is referenced by the firefighter speeding due to the feeling of safety he/she has in a modern firetruck, subsequently creating a hazardous situation and reducing the safety of the pedestrian.
  • 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.
    • This is referenced by languages with a word for "firefighter" giving a quicker reaction. If Cueball speaks (or is currently thinking in) a language without a word for "firefighter", he might be slower to recognize the role and authority of the driver warning him, and thus slower to react to the danger.
  • 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.
    • This is referenced by the tonal language being a language Cueball thinks he is fluent in but isn't.
  • 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.
    • This is referenced by Cueball diving out faster if the driver screams "red!" than if the driver screams "green!", as the firetruck is red and therefore it may create a moment of confusion for Cueball if the driver shouts "green!". It may also reference the common usage of "red" as indicating fire or danger, while "green" indicates safety.

This comic is probably a comment on the "replication crisis" in social psychology which has been in the news recently. For example, studies finding that merely thinking about intelligent people (e.g., writing down the attributes of a professor) will actually improve performance on math tests were once widely believed, and this "intelligence priming" effect is even included in textbooks. However, recent attempts to reproduce these effects have mostly failed and this failure to replicate is true of many social priming effects as well as other experiments in social psychology. Randall is also mocking the complicated, or even convoluted, setups often used in these experiments.

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.

Many other XKCD strips have commented on the ease with which surprising and novel, but false, results can be published in the scientific literature, such as 1478 and 882.

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.



New here?

Feel free to sign up for an account and contribute to the explain xkcd wiki! We need explanations for comics, characters, themes, memes and everything in between. If it is referenced in an xkcd web comic, it should be here.

  • List of all comics contains a complete table of all xkcd comics so far and the corresponding explanations. The red links (like this) are missing explanations. Feel free to help out by creating them!


Don't be a jerk. There are a lot of comics that don't have set in stone explanations, feel free to put multiple interpretations in the wiki page for each comic.

If you want to talk about a specific comic, use its discussion page.

Please only submit material directly related to—and helping everyone better understand—xkcd... and of course only submit material that can legally be posted (and freely edited.) Off-topic or other inappropriate content is subject to removal or modification at admin discretion, and users posting such are at risk of being blocked.

If you need assistance from an admin, feel free to leave a message on their personal discussion page. The list of admins is here.

Explain xkcd logo courtesy of User:Alek2407.

Personal tools


It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal or Bitcoin?