How to identify a subject matter expert

Let's start with a correlation.

We learn very few new words as we age and by no means it is because most of us have exhausted the word list.

I can always learn, by brute force, all the possible words that make me look like a semanticist, but I won't be able to use it complacently when I want to expresses myself in the most excruciatingly exquisite manner. (You see what I just did there :-))

Now!

This is very similar to what we do during the interview process to know if the candidate has hands on experience in that subject-matter or not, we look for the breadth as opposed to the depth of knowledge in a certain topic . This is because you can learn in-depth a concept over a few weeks, but it is almost impossible to learn the breadth of that topic. For instance, a candidate can learn about learning-and-development overnight, but, he won't be able to learn the philosophies of learning and the science behind the grasp of knowledge because that can only be gained with actual case-based work experience.

So, that's how you understand the difference between a subject-matter-expert and a want-to-be-an-expert.