Effective creative work requires both "hot" (exploratory) and "cool" (exploitative) thinking. Unfortunately, many people (especially novices) under-explore, jumping to the "cool'' part too quickly, because they assume their current thinking "has to be" the path. This paper presents empirical results of how metaphorical problem framing scaffolds can influence creative performance. The task used De Bono's "Thinking Hats." In a between-subjects experiment comparing exploratory to exploitative problem frames, the exploratory problem frame led to more original designs and more diverse ideas during brainstorming. This work provides an empirical baseline of how -- even for short tasks -- assigning people responsibility for broad thinking leads to better creative work.