Getting Out of the “I Don’t Know” Trap
There are two kinds of "I don't know." One kind is accompanied by a sense of bafflement and annoyance. If you put the feeling into words, it would say, "why would you expect me to know that?" That's how you feel when someone asks, "who's the president of Kyrgzstan?"
The other kind of "I don't know"--the more important and interesting kind--is accompanied by surprise and maybe chagrin, because you believe you should know the answer. For example, someone asks, "who was the US president in 1940?" and you go blank. Or a recruiter asks, "what makes you a good candidate for this job?" and no coherent thought comes to mind. When the answer "should" be "obvious," it's discomfiting that you have no answer.
In this situation, rookies make the mistake of repeating the question to themselves, loudly and insistently, hoping the answer will pop into mind. Occasionally it does. When it doesn't, rookies give up. They fall into the trap of believing that they don't know.
More likely, you do know enough to answer this question. When a direct question doesn't trigger a direct answer, you need to switch to an indirect process.
The indirect process is thinking. You work out an answer, by thinking through what you do know, over several steps.
The first step is to ask yourself an easier question--one that you can answer. By answering an easier question, you bring to mind memories and ideas that are relevant. Just one or two easier questions usually triggers enough useful information for you to use to get an answer to your "I don't know."
One good way to generate an easier question is to make a specific question more general, or a general question more specific. For example, switch from "who was president?" (a specific question) to "what was going on in general in 1940?" Answer: World War II had recently started in Europe. That may well trigger that FDR was president of the US then.
Another way to generate an easier question is to be a contrarian. Instead of looking for the good, look for the bad, and vice versa. For example, if you switch from "what makes you a good candidate for this job?" to "what would make someone a bad candidate?" you will likely think of a host of weaknesses: laziness, incompetence, ignorance. You can then contrast these negatives with your own productive, talented self to answer the recruiter's question.
It takes skill to think up a useful easier question at the moment you are surprised by "I don't know." People who think well "on their feet" have the skill and the presence of mind to ask an easier question and to remain poised, despite feeling stumped.
If you want to develop this skill, practice at your desk. Ask yourself the hard questions you expect from a recruiter or a boss or a listener. If you don't know an answer, take a few minutes to think through some easier questions until you can answer that hard question. Over time, you will become adept at answering questions, despite an initial "I don't know."