In 2003, Charlan Nemeth, a professor of psychology at the University of California at Berkeley, divided two hundred and sixty-five female undergraduates into teams of five. She gave all the teams the same problem—“How can traffic congestion be reduced in the San Francisco Bay Area?”—and assigned each team one of three conditions. The first set of teams got the standard brainstorming spiel, including the no-criticism ground rules. Other teams—assigned what Nemeth called the “debate” condition—were told, “Most research and advice suggest that the best way to come up with good solutions is to come up with many solutions. Freewheeling is welcome; don’t be afraid to say anything that comes to mind. However, in addition, most studies suggest that you should debate and even criticize each other’s ideas.” The rest received no further instructions, leaving them free to collaborate however they wanted. All the teams had twenty minutes to come up with as many good solutions as possible.
The results were telling. The brainstorming groups slightly outperformed the groups given no instructions, but teams given the debate condition were the most creative by far. On average, they generated nearly twenty per cent more ideas. And, after the teams disbanded, another interesting result became apparent. Researchers asked each subject individually if she had any more ideas about traffic. The brainstormers and the people given no guidelines produced an average of three additional ideas; the debaters produced seven.
Nemeth’s studies suggest that the ineffectiveness of brainstorming stems from the very thing that Osborn thought was most important. As Nemeth puts it, “While the instruction ‘Do not criticize’ is often cited as the important instruction in brainstorming, this appears to be a counterproductive strategy. Our findings show that debate and criticism do not inhibit ideas but, rather, stimulate them relative to every other condition.” Osborn thought that imagination is inhibited by the merest hint of criticism, but Nemeth’s work and a number of other studies have demonstrated that it can thrive on conflict.