I'm doing a bit of work at the agency at the moment about improving brainstorming processes, and I discovered something quite interesting / alarming over the weekend, which I will share with you here.
It has not been shown that brainstorming improves either the quantity or quality of ideas for solutions to a given problem over the same number of people working separately. In fact that needs saying again. THERE IS NO EVIDENCE THAT BRAINSTORMING IMPROVES THE QUANTITY OR QUALITY OF IDEAS.
Here's a nice looking slide from Will Lion at Dare
Surprising eh? We tend to use brainstorming so much in a business environment that we don't consider whether it is actually an effective use of anyone's time. The key alternative is telling here, get the same number of people for the same number of minutes to write down all the ideas that come to them and you will have at least as many and at least as varied a range of proposals than in a single group.
A main reason for this is something called 'production blocking'. Explained simply, if one person is telling their idea to the group the other members of the group are unable to mention their ideas, and also have their thinking ability limited by the need to listen to the active participant. This means effectively at any one time, there is only one person working at full speed, and others impaired to one degree or another.
One partial solution is to keep your group small, the less people there are in the brainstorm, the less overall decrease in output from production blocking. For instance if there are more than 6-7 people, consider splitting down into two groups.
There are also some other techniques that seem to improve overall output, by focusing on trying to increase the amount of time each participant can spend working. One method that looks interesting is called 6-3-5 brainwriting. Essentially, you get six people (6), each person has to write three ideas (3) every five minutes (5) for half an hour. There are various different methods like card passing or what-have-you to ensure that everyone is exposed to everyone else's ideas, and participants are encouraged to build on other ideas that have already come up. One simple solution might be everyone gets their own flipchart, or piece of paper on the wall.
Another approach is to get people to work on the problems beforehand and bring their solutions to the workshop, and use the time together for what group sessions have been shown to be useful for, building on other peoples work, and identifying and evaluating the best options.