Why would a student at first find a problem impossible to solve when later the solution is obvious?

Question

Quizplus · Accepted Answer

The most likely reason for a student to find a problem impossible to solve initially but then see an obvious solution later is that they had an unconscious assumption or bias that was blocking their thinking. Once they were able to identify and overcome this assumption or bias, the solution became apparent. The other choices, such as not having studied a particular subject, would only be relevant if the problem specifically involved that subject matter.

Why Would a Student at First Find a Problem Impossible