Brainstorming rules as assigned goals: Does brainstorming really improve idea quantity?

In two experiments (n = 264 and 339), I treat brainstorming rules as assigned goals and compare their effectiveness to that of quantity goals as interventions to improve the number of ideas generated by individuals. Controlling for goal commitment, I find that brainstorming rules alone do not convey an advantage over even a vague quantity goal presented alone for enhancing the number of ideas generated in two common tasks. Detailed contrasts revealed that specific, difficult goals were only partially effective on their own, as expected when goal commitment is moderate. However, I find evidence in both studies that brainstorming rules are useful adjuncts to specific, difficult quantity goals. Importantly, their combination was the only consistently effective improvement over both vague quantity goals and brainstorming rules presented alone. I discuss implications for future research adopting a goal-based view of intervention in idea generation.