The ludic fallacy occurs when someone presumes that what would be true under controlled conditions, such as a game, computer model, or research lab, will be true in the world outside of those controlled conditions.

Here is an example:

Magistrate: "Those with the brightest minds and deftest hands have tried for years to untie the large knot in this rope, and all have failed. I therefore believe it will never be loosened." ​Alexander (heaves his sword and brings it down through the knot): "There."

The magistrate presumed that Alexander would abide by the "rules of the game" and only use his fingers to try loosening the knot. ​Alexander violated custom (but not the law) by using his sword.

Here is another example:

Dr. Genius and Plumber Jane watch Albert flip a coin 50 times, and they see it come up heads every time. ​Albert says,"This is a fair coin. How many times do you think it will come up tails in the next ten flips?" ​Dr. Genius says, "Since it is a fair coin, past results have no bearing on future occurrences, so odds are, it will be tails five of the next ten times." ​Jane says, "I refuse to believe it is a fair coin. I say it will come up tails zero times in the next ten flips."

Who do you think is right? If it were a truly fair coin, Dr. Genius would be right. But that is not what Jane thinks is happening. Essentially, Jane suspects that Dr. Genius is committing the ludic fallacy.