Brainstorming and creativity has increasingly become a group process.However, Lehrer's article in 'The New Yorker' contends that brainstorming groups think of fewer ideas than individuals working alone. Rather, it is better for individuals to work alone and then pool their ideas. One of the problems with group think is that people are usually encouraged not to 'criticise' the ideas of others in the group.
On the contrary, creativity often thrives on criticism because conflict drives creativity. If you want to be creative you have to get past the top layer of predictability. Read the article at:http://www.newyorker.com/reporting/2012/01/30/120130fa_fact_lehrer?currentPage=all