Hofstadter's law was a part of Douglas Hofstadter's 1979 book Gödel, Escher, Bach: An Eternal Golden Braid. The law is a statement regarding the difficulty of accurately estimating the time it will take to complete tasks of substantial complexity. It is often cited amongst programmers, especially in discussions of techniques to improve productivity, such as The Mythical Man-Month or extreme programming. The recursive nature of the law is a reflection of the widely experienced difficulty of estimating complex tasks despite all best efforts, including knowing that the task is complex.
The law was initially introduced in connection with a discussion of chess-playing computers, where top-level players were continually beating machines, even though the machines outweighed the players in recursive analysis. The intuition was that the players were able to focus on particular positions instead of following every possible line of play to its conclusion. Hofstadter wrote: "In the early days of computer chess, people used to estimate that it would be ten years until a computer (or program) was world champion. But after ten years had passed, it seemed that the day a computer would become world champion was still more than ten years away". He then suggests that this was, "just one more piece of evidence for the rather recursive Hofstadter's Law."[clarification needed]