Hindsight bias is the inclination to see events that have occurred as more predictable than they in fact were before they took place. Hindsight bias has been demonstrated experimentally in a variety of settings, including politics, games and medicine. In psychological experiments of hindsight bias, subjects also tend to remember their predictions of future events as having been stronger than they actually were, in those cases where those predictions turn out correct.
Prophecy that is recorded after the fact is an example of hindsight bias, given its own rubric, as vaticinium ex eventu.
One explanation of the bias is the availability heuristic: the event that did occur is more salient in one’s mind than the possible outcomes that did not.
Therefore, when one learns that a Quagmire III Vigenere cipher was used on the first part of Kryptos and the second; it is easy for many to say, “Oh, well of course it was, how come they didn’t get that earlier?”. The reality is that they were faced with the cryptic Morse code phrases and a big piece of Copperplate. Attempts at frequency analysis would likely have started with all 866 letters. Even with the tableau side, an analyst would still need to attempt to determine the key length and attempt to determine the right keyword. There’s a reason it took David Stein 7 years with pencil and paper and that’s because the process can be exhaustive. While they are vulnerable to analysis, someone without the knowledge we possess today would still need to determine if they thought the copperplate was a vigenere cipher and after it failed to translate the entire thing, they would need to re-assess and decide what they thought the next section was and so on. There are some very smart people in the world that would scoff at this paragraph but that’s exactly the point. Kryptos wasn’t just meant for the very talented, the very experienced or the very intelligent. It was meant for the everyday workers of the CIA and it can be assumed that they were believed to have a decent chance at solving it.
We will inevitably see this bias in effect after K4 has been solved when a large section of those who care will be yelling, “Ah! Of course, of course that’s what it was!” while the rest of us mutter under our breath.