Once learned, some bits on knowledge are so intrinsic to one's job or skill that one cannot remember what it felt like without that knowledge (and therefore difficult to document or teach to newcomers).
What is the name for this phenomenon?
Once learned, some bits on knowledge are so intrinsic to one's job or skill that one cannot remember what it felt like without that knowledge (and therefore difficult to document or teach to newcomers).
What is the name for this phenomenon?
I would call it tacit or implicit knowledge, for which a good definition is
That seems to fit OP's context very well, in that it's not easily communicated to others.
This may be called procedural knowledge:
In cognitive psychology, procedural knowledge is the knowledge exercised in the accomplishment of a task, and thus includes knowledge which, unlike declarative knowledge, cannot be easily articulated by the individual, since it is typically nonconscious (or tacit). Many times, the individual learns procedural knowledge without even being aware that they are learning (Stadler,1989).
It's also known as tacit knowledge:
Tacit knowledge (as opposed to formal or explicit knowledge) is the kind of knowledge that is difficult to transfer to another person by means of writing it down or verbalising it.
In a similar, more general, vein is situated knowledge:
Situated knowledge is knowledge specific to a particular situation.
[...]
Knowledge generated through experience is called knowledge "a posteriori", meaning afterwards.
In a less technical sense, I might simply call it wisdom, though this may not connote the full intent of your meaning. From the perspective of a novice, the knowledge may be recondite or abstruse. If you're looking for a word to describe the difficulty in learning a job or skill, you might say it has a steep learning curve.
Without sounding flippant, I would say that this "phenomenon" is learning itself (or, the learning process). I'm sure there is an academic journal out there where educators have coined a gussied up term for obstacles encountered by a mentor imparting knowledge, but I don't know of it.
I find the title of your question and the contents of its body to be slightly at odds with each other.
... bits on knowledge are so intrinsic to one's job or skill that one cannot remember what it felt like without that knowledge (and therefore difficult to document or teach to newcomers)
I would simply call this experience.
Term for knowledge that is unintuitive but obvious in retrospect
I would call this a trick or a knack.
Engineers learn heuristics that have not always been traditionally documented, but part of modern education is to teach them and understand their limitations.
I realize you use this adjective in your question, but I'd like to add intrinsic knowledge to the list. According to one website:
Intrinsic knowledge is what you know without even realizing that you know it. It is the knowledge and thought processes that you take for granted that you think everyone knows but that they really don’t.
As for using it to describe a skill obtained some time ago, this blogger makes a similar analogy:
An example for intrinsic knowledge can be represented by a kid that is learning how to ride a bicycle. Maintaining balance while riding a bicycle cannot be taught by someone because every person has a different technique to perform the act. It is an experience and a perception that the person has after having hours or even days of practice. After a while the child will be riding the bike without any difficulty because that is the kind of knowledge the kid has but doesn’t know he or she has inside. This portrays intrinsic knowledge that is what the person knows without even realizing that he or she knows it. It is the knowledge and thought processes that people take for granted and think everyone knows but that they really don’t.
Are you looking for the term internalised knowledge? Knowledge that an individual may not be consciously aware of while accomplishing tasks.
You now have an innate ability.
I would specifically point to meaning 3 from the website:
originating in or arising from the intellect or the constitution of the mind, rather than learned through experience