Problem solving is not the same thing as brainstorming. Brainstorming is deliberately loosely structured and undirected. A group of engineers huddled around a whiteboard or a monitor are exactly the opposite: highly focused on the details of a single problem.
If you can find a copy of 59 Seconds, by Richard Wiseman, it's mentioned in there (with references, if I remember correctly). I don't have my copy handy.
