Name of the psychological effect that make us see correlation that may not exist

Question

After 51 years, the "Z-340" cypher text from "Zodiac" serial killer has been solved: https://edition.cnn.com/2020/12/11/us/zodiac-killer-cypher-340-code-trnd/index.html

Now that we have the problem and the solution, when I'm watching the cypher text again I'm like "Ho.. look, look, it's so obvious! The sign must mean this and that and the following letter is transposed according to the sign and if you like at this and that there is a clear relationship between the age of the captain and whatever this thing mean!! Ha! It must be!"

Even knowing that it's just wishful thinking, I'm still willing it to be true: "Yeaaah, it's probably, 99.99% sure, just me imagining things.. BUT! That 0.01% doubt, I want it to be true anyway."

There is a name for this effect. I don't think it's the Barnum effect, it may or may not be a "confirmation bias". What is this effect called?

Answer 1

The feeling that the solution is obvious after it is provided is called hindsight bias (aka the "knew-it-all-along phenomenon").

This feeling is informed by the metacognitive sense of surprise, which itself is a form of processing fluency. Basically, when the solution to a problem is first given, it is surprising (lacks fluency), and hence judged as difficult. However, when the solution is known or provided again, it is no longer surprising (has fluency), and hence judged as easy. People often underestimate the difficulty (or predictability) of solutions (or events) after knowing the outcome, due to this bias.

In the example provided in the question however, it is not clear that you actually know the solution, only that you feel that you know the solution after it was solved by someone else. In this case, you really do have a case of wishful thinking.