Brainstorming: The Four Rules, What the Research Says and the Variants That Work

Brainstorming is a technique for generating a large number of ideas about a problem in a short time by keeping idea generation separate from evaluation. Advertising executive Alex Osborn created it in the late 1930s, and it rests on four rules: go for quantity, defer judgment, welcome unusual ideas, and combine and build on other people’s ideas.

It is the default idea-generation method in organizations, it is widely used in higher education, and it is one of the most researched creative techniques. The research brings good news and awkward news. The principles work, but the way brainstorming is usually run in groups wastes much of its potential. This guide sums up what the evidence says and how to run a session that pays off.

Where Brainstorming Comes From

Alex Osborn (1888–1966) was an executive at BDO, the advertising agency he formed in 1919. By his own account, in 1938 he began running sessions of “organized ideation” at the firm, which participants nicknamed brainstorm sessions: using the brain to storm a problem. Osborn spread the technique through books such as Your Creative Power (1948) and Applied Imagination (1953), founded the Creative Education Foundation in Buffalo and, with the academic Sidney Parnes, developed the Creative Problem Solving (CPS) process.

His underlying idea was as influential as the technique itself: creativity is not the gift of a tiny minority, but something any individual or group can channel deliberately to solve problems. Osborn also designed brainstorming to counter a very human habit — calling off the search for solutions too early.

The Four Rules of Brainstorming

1. Quantity first. Generate as many solutions as possible.
2. Defer judgment. Nobody evaluates or criticizes ideas until the generation stage is over.
3. Welcome original ideas, including the ones that seem wild.
4. Combine and improve. Build on the ideas already on the table.

The second rule is the heart of the method. Osborn was emphatic: “No conference can be called a brainstorming session unless the deferment-of-judgment principle is strictly followed” (Osborn, 1963, p. 152, as cited in Puccio & Holinger, 2020). Keeping the divergent stage (producing options) apart from the convergent stage (choosing among them) is the same logic explained in our article on divergent vs. convergent thinking.

What the Research Says

Deferring judgment works. It was one of the first creativity principles put to an experimental test. In 1959, Meadow, Parnes and Reese found that groups following the rule produced significantly more good ideas than groups told to focus on quality from the start. Parnes and Meadow found a similar effect with people working alone: those who evaluated while generating came up with fewer high-quality ideas.

The problem is the group, not the technique. The accumulated evidence shows that the pooled ideas of people working separately — so-called nominal groups — beat those of groups brainstorming together by a wide margin, in both quantity and quality. A review by Diehl and Stroebe (1987) covered 22 studies: in 18, nominal groups produced more ideas; the remaining four, all with two-person groups, found no difference. In the six studies that rated quality, nominal groups also came out ahead.

Three mechanisms explain the loss:

• Production blocking: while one person talks, the others wait their turn and forget or drop ideas. This is the biggest factor.
• Evaluation apprehension: fear of other people’s criticism holds participants back.
• Free-riding: some participants put in less effort when responsibility is shared.

Byron also describes what he calls “creativity fatigue”, observed in brainstorms with groups of PhD students: a point at which participants simply don’t want to think about new ideas any more. To explore it, he asked participants to record their own creative state at regular intervals on a “creativity thermometer”, a chart adapted from the Yerkes–Dodson curve of performance versus arousal.

According to Kevin Byron (2012), group brainstorming stays popular partly because of the illusory belief that groups always out-produce individuals working apart. Even so, it has real social value: it builds collaboration and a shared sense of ownership over ideas. The key is to run it better.

An open debate. Some recent work argues that debate and simultaneous criticism actually stimulate ideas. Puccio and Holinger (2020) counter that the main study behind that claim is methodologically flawed, and they defend deferral of judgment.

How to Run a Brainstorming Session That Works

1. Present the challenge and the four rules before you start, so everyone knows that nothing gets evaluated at this stage.
2. Begin with a few minutes of individual writing. Brainwriting — writing ideas down individually within a group session — narrows the gap with nominal groups.
3. Pool the ideas with a facilitator. In the studies, trained facilitators who asked people to stay focused, avoid telling stories, avoid explaining ideas, keep the conversation going, invite everyone to contribute and hold back criticism considerably reduced the productivity loss.
4. Take short breaks when the pace drops. Sessions lose steam quickly, and short breaks improve productivity.
5. Fit the technique to the problem. For a complex challenge full of conditions, start by listing the constraints; for a simpler one, start by generating ideas freely.
6. Evaluate later, in a separate stage, with explicit criteria, to select and develop the strongest ideas.

Brainstorming Variants

Bonnardel and Didier (2020) list several variants used in the early stages of design:

• Brainwriting: ideas are written down instead of spoken.
• Brainsketching: ideas are drawn.
• Post-up brainstorming: the session runs on sticky notes.
• Challenge-storming: participants look for ideas that break with existing product paradigms.
• Reverse brainstorming: used to analyze the causes of a problem.

In their own study, the authors compared two variants with design students and future teachers: one focused on generating ideas, the other on listing the problem’s constraints. Design students, who faced a complex task, produced projects that were better adapted and more feasible when they started from the constraints. Future teachers, working on simpler tasks, benefited more from the idea-focused variant. The takeaway: there is no single right way to brainstorm, only versions to fit to the group and to the complexity of the task.

Common Mistakes

• Criticizing during generation. It breaks the central rule and triggers evaluation apprehension.
• Speaking only in turns. Without time to write, production blocking swallows ideas.
• Long sessions with no breaks. Creative fatigue sets in sooner than people expect.
• Always using the same format. The kind of problem and the people in the room change what works.

For more techniques to pair with brainstorming in class, see these 5 creative thinking techniques for university educators.

FAQ

Who invented brainstorming?

Alex Osborn, an American advertising executive. He started using it at his agency in 1938 and popularized it in books published in the 1940s and 1950s.

Does brainstorming work better in groups or alone?

Research shows that people generating ideas separately produce more and better ideas, in total, than traditional brainstorming groups. The most effective approach combines both: individual written ideation first, then a facilitated group stage.

What is the most important brainstorming rule?

Defer judgment. For Osborn, a meeting without it simply wasn’t brainstorming, and the first experiments supported its effect.

What is brainwriting?

A variant in which each person writes ideas down instead of saying them aloud. Because nobody has to wait for a turn, it reduces production blocking.

Learn to Use It With Method

In the creativity course, brainstorming shows up twice: in Week 5, to learn its basic techniques, and in Week 13, to apply it to idea generation for your own project. You practice it alongside lateral thinking, mind maps and SCAMPER.