Answer:This is an example of LEARNED behavior.
Explanation:
A learned behavior refers to how we develop particular knowlegde due to exposure to it and our experience. It is an opposite of innate behavior which is the one we acquire through our genes such that we can perform that behavior without an experience.
David kept being exposed to the clue and over time he was experienced or too familiar with it that he had learned it and could remember it without any reference to the note.