What is brainstorming?
Last reviewed by The thinkdrop facilitation team
Brainstorming is a structured group technique for producing a large number of ideas about one specific question before any of them are judged. Alex Osborn described it in 1953 with four rules: defer criticism, welcome wild ideas, aim for quantity, and combine and improve on others' ideas. Evaluation happens afterwards, as a separate step.
Key facts
- Coined by
- Alex Osborn, Applied Imagination (1953)
- Original rules
- 4 — defer judgement, wild ideas, quantity, build on others
- Typical group size
- 4–8 participants
- Typical length
- 45–60 minutes
- Core principle
- Separate generating from judging
- Main failure mode
- Evaluating ideas while still generating them
Step by step
- Start from a question, not a topic — Brainstorming is aimed at a single, answerable question. "Retention" is a subject; "What makes a customer cancel in month two?" is a brainstorming question. The narrower the question, the more concrete the ideas.
- Defer judgement — No critique, no "we tried that", no cost objections during generation. This is the rule that produces the volume; it is also the one groups break first, usually within the opening two minutes.
- Welcome wild ideas — Impractical ideas are cheap and they widen the range the group is willing to consider. It is far easier to tame an extreme idea than to make a cautious one interesting.
- Go for quantity — Quantity is the proxy you can actually manage. Set a visible target — 40 cards, say — because groups that chase a number stop self-editing and the later ideas are usually the less obvious ones.
- Combine and improve — Ideas belong to the board, not their author. Read what others wrote and extend it: "yes, and" rather than "no, but". Most usable outcomes are a merge of two half-ideas.
- Judge in a separate pass — Once generation stops, switch modes explicitly: group into themes, react or vote, then pick the two or three worth owning. Announce the switch out loud so nobody is still generating while others are critiquing.
Group brainstorming vs individual brainstorming
Decades of research on "production blocking" find that the same people writing ideas alone produce more distinct ideas than they do talking in one room, because only one person can speak at a time and everyone else is holding their thought. The practical answer is not to abandon the group but to write first and talk second: silent generation captures the range, discussion combines and improves it.
When brainstorming is the wrong tool
Brainstorming produces options. It does not produce decisions, and it is a poor fit for questions that already have a correct answer.
- The question has one verifiable answer — research it instead.
- The decision is already made and the meeting is looking for agreement — say so instead.
- The group lacks the context to have an opinion — brief them first, brainstorm later.
- The real constraint is capacity, not ideas — prioritise the backlog instead.
Where the technique came from
Alex Osborn, an advertising executive, formalised brainstorming in Applied Imagination in 1953 after running "think-up" sessions at his agency. His central claim was that judgement suppresses imagination, so the two activities must be separated in time. Almost every modern variant — brainwriting, crazy 8s, six thinking hats — is a different mechanism for enforcing that separation.
Brainstorming formats compared
| Format | How it works | Best for |
|---|---|---|
| Classic verbal | Group calls out ideas, one scribe | Small, high-trust groups |
| Brainwriting | Everyone writes silently, then swaps | Mixed seniority, quiet teams |
| Online board | Everyone posts cards at once | Remote and hybrid groups |
| Asynchronous | Board open for 24h, then a short call | Distributed timezones |
Frequently asked questions
What is brainstorming in simple terms?
Generating as many ideas as possible for one question, with all judgement postponed until afterwards.
What are the four rules of brainstorming?
Defer judgement, welcome wild ideas, aim for quantity, and build on other people's ideas.
Who invented brainstorming?
Advertising executive Alex Osborn, who published the method in Applied Imagination in 1953.
Is brainstorming actually effective?
Yes when generation is silent and individual first, and less so when the group only talks, because people block each other.
What is the difference between brainstorming and ideation?
Ideation is the whole process of creating and refining ideas; brainstorming is one technique used inside it.