This is definitely a problem. I don't think it's a sign of dim intelligence, or even not paying attention. It may be a sign of nervousness, or simply of being a

This is definitely a problem. I don't think it's a sign of dim intelligence, or even not paying attention. It may be a sign of nervousness, or simply of being an introvert (like myself). They may still be very good people. Part your job as an interviewer is to draw them out enough for you to figure that out. They may not understand what you're looking for in their answers. Did you tell them when you asked? It was obvious to you, but it may not be obvious to them. Once I get a few of these answers, I try to ask questions that require more background explanation to respond to. This requires some thinking on your part. If you've seen a project like theirs before, you can ask them how they solved some of the problems that you ran into on your own project. "Did you consider X? What would happen if..." If you are actively engaged and thinking, people will respond to that, much more than if you ask very open-ended questions like, "Tell me about X."