Can negativity improve brainstorming?:

Yes.

Research has consistently demonstrated that individuals tend to outperform groups on idea-generation tasks (e.g., Mullen, Johnson, & Salas, 1991). However, mood states have the capacity to alter the coordination and motivation of group members, leading to performance gains or performance losses. In this experiment, individuals and 3-person groups generated slogans for a fictitious company after experiencing a positive or negative mood induction. Contrary to previous research, negative mood groups in our study actually generated slogans that were more creative than those produced by negative mood individuals. No differences emerged for positive individuals and groups. In the negative conditions, the effect of level of analysis (individual vs. group) on creativity was mediated by persistence on the slogan-generation task. Results are presented in the context of feelings-as-information (N. Schwarz & G. L. Clore, 1988). (PsycINFO Database Record (c) 2009 APA, all rights reserved)

Source: No pain, no gains: Negative mood leads to process gains in idea-generation groups. from Group Dynamics: Theory, Research, and Practice – Vol 13, Iss 4 by Jones, Eric E.; Kelly, Janice R.