[gte910h]

The skill you're looking for here is called meta-knowledge. It is knowledge of your level of knowledge about a given topic.

It is a teachable trait, arguably what very selective schools with hard grading curves teaching difficult things teach people to develop (as you have to determine what you don't know to pass/excel/etc there).

I've always personally believed the test: "What would you need to get going on these 5 projects?" Is a great question. If talking about researching X Y or Z don't come out of the candidate's mouth (and it's not an old solved problem, like self-contained embedded C code), you mark them down as less meta-knowledgeable. (Doesn't mean unhireable, but you don't want them in highly independent positions or constantly learning new things; people with low meta knowledge appear to actually be quite happy in places that high meta people hate, such as long term maintenance programming).

In software particularly, study of estimation (and it's continual use) can teach people the practice of evaluating all risks, including metaknowledge. I like the book: http://www.amazon.com/Software-Estimation-Demystifying-Pract... (non-aff link) for getting people going with the practice.