Falacias: Texas Sharpshooter

The Texas sharpshooter fallacy is a logical fallacy in which information that has no relationship is interpreted or manipulated until it appears to have meaning. The name comes from a joke about a Texan who fires some shots at the side of a barn, then paints a target centered on the biggest cluster of hits and claims to be a sharpshooter.


The fallacy does not apply if one had an ex ante, or prior, expectation of the particular relationship in question before examining the data. For example one might, previous to examining the information, have in mind a specific physical mechanism implying the particular relationship. One could then use the information to give support or cast doubt on the presence of that mechanism.

Alternatively, if additional information can be generated using the same process as the original information, one can use the original information to construct a hypothesis, and then test the hypothesis on the new data. See hypothesis testing. What one cannot do is use the same information to construct and test the same hypothesis — to do so would be to commit the Texas sharpshooter fallacy.
The fallacy is related to the clustering illusion, which refers to the tendency in human cognition to interpret patterns in randomness where none actually exist.

Examples

• Attempts to find cryptograms in the works of William Shakespeare, which tended to report results only for those passages of Shakespeare for which the proposed decoding algorithm produced an intelligible result. This could be explained as an example of the fallacy because passages which do not match the algorithm have not been accounted for.
• The fallacy could also be an explanation for cryptograms in the Bible.
• This fallacy is often found in modern-day interpretations of the quatrains of Nostradamus. Nostradamus's quatrains are often liberally translated from the original (archaic) French, stripped of their historical context, and then applied to support the conclusion that Nostradamus predicted a given modern-day event, after the event actually occurred.

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