Brainstorming: Method, Rules, Variants, and What Research Really Shows

Brainstorming is a creativity technique for group ideation in which participants generate as many ideas as possible about a defined problem while deferring all judgment. The method was systematically described in 1953 by Alex F. Osborn, an advertising executive and co-founder of the agency BBDO, in his book Applied Imagination [1].

Brainstorming is arguably the most well-known creativity technique in the world — and simultaneously the most misunderstood. Nearly every team has “brainstormed” at some point. But very few adhere to the four core rules Osborn defined. And even fewer know the research findings that since the 1950s have shown that classic group brainstorming under certain conditions produces fewer ideas than individuals working alone [2].

This sounds paradoxical. If brainstorming doesn’t work the way most people practice it, why is it used everywhere? The answer: because the method itself isn’t the problem. The problem is naive application without understanding its strengths, weaknesses, and variants.

In our consulting practice for service innovation, we use brainstorming as one of several ideation techniques — typically in the early concept phase of our Integrated Service Development Process (iSEP), when divergent thinking is needed and idea quantity takes priority over elaboration. This guide explains when brainstorming is the right choice, when you should reach for a variant instead, and what you can take from 70 years of research into your practice.

Alex Osborn and the birth of brainstorming

Alex F. Osborn (1888—1966) was not a scientist but a practitioner. As co-founder of the advertising agency Batten, Barton, Durstine & Osborn (BBDO), he sought a method to systematically improve creative ideation in teams. His central observation: in conventional meetings, ideas are immediately evaluated and criticized before they can develop. The fear of negative feedback blocks precisely the unusual ideas that lead to breakthroughs [1].

In 1939, Osborn introduced the first “brainstorm sessions” at BBDO. In 1953, he published Applied Imagination, the definitive work on the method. The term “brainstorming” — literally “brain storm” — describes Osborn’s ideal: a storm of ideas sweeping over the team without regard for conventions.

The method spread rapidly through the American business world of the 1950s. But as early as 1958, Taylor, Berry, and Block published the first controlled study showing that nominal groups (individuals whose ideas are aggregated afterward) produce more and better ideas than interactive brainstorming groups [2]. This launched a research controversy that continues to this day.

The 4 core rules according to Osborn

Osborn defined four core rules that every brainstorming session must follow. In practice, at least two of them are regularly violated — with predictable consequences.

Rule 1: Defer judgment

During ideation, no idea is evaluated, commented on, or criticized — neither verbally nor nonverbally. This also means: no eye-rolling, no frowning, no “Yes, but…”

Why this matters: Research shows that evaluation apprehension is one of the three main reasons why brainstorming groups produce fewer ideas than individuals [3]. The mere expectation of being evaluated reduces idea production — even when nobody actually criticizes.

Facilitation tip: Say explicitly at the start: “For the next 20 minutes, there are no bad ideas. If anyone evaluates an idea — even positively with ‘great idea!’ — I’ll interrupt. Evaluation comes afterward.” Even positive evaluations create an implicit standard that subsequent ideas must measure up to.

Rule 2: Go for quantity

The goal is the greatest possible number of ideas. The premise: the more ideas, the higher the probability that truly novel ones are among them.

What the research shows: Osborn’s premise has been empirically confirmed. Studies show a positive relationship between the total number of ideas generated and the number of high-quality ideas [4]. The mechanism: the obvious ideas come first. The truly creative ideas typically emerge in the second half of a session, when the obvious has been exhausted.

Rule 3: Build on ideas

Participants should pick up, develop, and combine the ideas of others. Osborn’s metaphor: use others’ ideas as a “springboard.”

In practice: This mechanism is the actual advantage of group brainstorming over individual work. Cognitive psychologists call it cognitive stimulation — another person’s idea activates associations you wouldn’t have had alone [5]. But this advantage only takes effect when the other three rules are followed.

Rule 4: Encourage wild ideas

The more unusual an idea, the better. Wild ideas can be tamed more easily than boring ideas can be made inspiring.

Facilitation tip: If you notice that all ideas remain in the realm of the obvious, ask a provocation question: “What if we had unlimited budget?”, “What would [company from a different industry] do?”, or “What would be the exact opposite of our current solution?”

The research controversy: Why groups produce fewer ideas

Since Taylor’s 1958 study, dozens of controlled experiments have produced a consistent finding: interactive brainstorming groups generate fewer ideas than the same number of individuals working alone [2][3]. This finding has been replicated so often that it is considered robust in creativity research.

Diehl and Stroebe (1987) identified three main causes [3]:

1. Production blocking

In a group, only one person can speak at a time. While others listen, they forget their own ideas or unconsciously discard them. In a 6-person group, each participant spends up to 80% of the time listening rather than thinking.

The consequence: The sheer mechanics of speaking blocks idea production — regardless of the group’s quality or the facilitation.

2. Evaluation apprehension

Despite the “defer judgment” rule, participants fear being negatively evaluated by the group. In hierarchical teams, this effect is particularly strong: when a senior leader is in the room, employees voice fewer and more conservative ideas [6].

3. Social loafing

In groups, individuals reduce their contribution because they assume others will pick up the slack. This effect is particularly strong in brainstorming groups because individual contributions are not identifiable [3].

What does this mean in practice?

The research doesn’t say brainstorming is useless. It says that unmodified group brainstorming is suboptimal — and that better variants exist that specifically address the three problems. We present the most important ones in the next section.

Research finding: A meta-analysis of 50 studies confirms: production blocking explains the largest share of productivity loss in brainstorming groups. Variants that reduce production blocking (especially brainwriting and electronic brainstorming) perform significantly better than classic verbal brainstorming [5].

6 brainstorming variants and when to use each

Variant 1: Classic brainstorming (Osborn method)

Process: 5-8 participants, one facilitator, 15-25 minutes. Ideas are voiced aloud, the facilitator records them visibly for everyone.

Strengths: Low entry barrier, high energy, strong cognitive stimulation.

Weaknesses: Production blocking, evaluation apprehension, dominance effects.

When to use: When the group already knows each other well, there is no strong hierarchy, and team energy matters more than maximum idea count.

Variant 2: Brainwriting (6-3-5 method)

Process: 6 participants each write 3 ideas on a sheet, pass the sheet along, 5 rounds. In 30 minutes, up to 108 ideas are generated.

Strengths: Eliminates production blocking entirely, drastically reduces evaluation apprehension, ideal for introverted teams and hierarchical cultures.

Weaknesses: Less real-time cognitive stimulation, since you read rather than hear others’ ideas.

When to use: When hierarchy, introversion, or dominance issues affect the group. Detailed guide: Brainwriting — The silent alternative to brainstorming.

Variant 3: Reverse brainstorming

Process: Instead of “How do we solve problem X?” ask: “How can we make problem X as bad as possible?” Then reverse the anti-ideas.

Strengths: Bypasses mental blocks, particularly effective with teams that are stuck and have “tried everything.” Participants often find it easier to identify failures than to develop solutions.

Weaknesses: Requires an additional reversal step whose quality depends on facilitation.

When to use: When the team has already thought about the problem multiple times and no new ideas are emerging. Particularly effective for improving existing services.

Variant 4: Round-robin brainstorming

Process: Each participant takes turns sharing one idea. Anyone who has no idea says “pass” and can contribute again in the next round.

Strengths: Ensures every participant gets heard. Prevents single individuals from dominating the session.

Weaknesses: Can create pressure (“It’s my turn and I can’t think of anything”), reduces spontaneity.

When to use: When one or two dominant voices control the room and quieter participants are overlooked.

Variant 5: Starbursting

Process: Instead of generating ideas, the team formulates questions about an existing idea — organized by the 6 question words: Who, What, When, Where, Why, How. The result is a question map, not an idea list.

Strengths: Shifts focus from solutions to problem understanding. Uncovers blind spots that get overlooked during ideation.

Weaknesses: Produces questions rather than direct solutions. Requires a downstream ideation step.

When to use: In the early phase of a project, when the problem itself is not yet well enough understood. Pairs ideally with Design Thinking, which also places problem understanding before solution development.

Variant 6: Electronic brainstorming (EBS)

Process: Participants enter ideas simultaneously via a digital tool (Miro, Mural, Google Docs, specialized EBS software). Ideas become visible to all in real time.

Strengths: Eliminates production blocking entirely (everyone types simultaneously), enables anonymity, scales to large groups (20+ participants).

Weaknesses: Less spontaneous energy than a physical meeting, requires digital tools and comfort with them.

When to use: With remote teams, large groups (>8 people), and when anonymity is desired. Dennis and Williams (2003) showed that electronic brainstorming in large groups produces even more ideas than nominal groups — a rare case where interactive brainstorming outperforms individual work [7].

Decision guide: Which variant fits?

Situation	Recommended variant	Why
Small, familiar group with no hierarchy gap	Classic brainstorming	Maximum cognitive stimulation
Hierarchical team or introverted culture	Brainwriting (6-3-5)	Eliminates dominance and evaluation apprehension
Team is stuck, “tried everything”	Reverse brainstorming	Bypasses mental blocks
Dominant individuals drown out the group	Round-robin	Forces equal participation
Problem not yet well understood	Starbursting	Shifts focus to problem understanding
Remote teams or large groups (>8)	Electronic brainstorming	Scales, enables anonymity
Maximum ideas in minimum time	Brainwriting or EBS	Parallel instead of sequential

Brainstorming in the context of service innovation

In the innovation process, brainstorming is neither a starting point nor an endpoint — it is a tool for the divergent phase. In a typical service innovation process like iSEP, it comes after user research and before structured concept development:

1. Upstream: User research (Discovery) — Interviews, observations, and jobs-to-be-done analyses identify user needs. Without this groundwork, the team brainstorms in a vacuum.
2. Brainstorming (divergent phase) — The team generates as many ideas as possible for how the identified needs could be addressed. Quantity counts here.
3. Downstream: Structured concept development — The best ideas are systematically refined, e.g., using the Morphological Box for structured exploration or the SCAMPER method for targeted improvement of existing concepts.

The most common process mistake: Teams brainstorm without prior user research. The result: the 50 best ideas address problems no customer has.

Practical example: Ideation for a digital onboarding service

Context: An insurance company wants to improve its onboarding process for new customers. User research has shown that 23% of new customers cancel within the first 90 days because they don’t understand their coverage and can’t find a contact person.

Brainstorming setup:

• Participants: 7 people (product management, customer service, IT, UX design, sales, one external customer)
• Variant: Combination of 10 minutes silent brainwriting (avoid production blocking) + 15 minutes classic brainstorming (leverage cognitive stimulation)
• Question: “How can we give new customers the feeling in the first 30 days that they made the right decision?”

Result after 25 minutes: 67 ideas, including:

• Personal video call on day 3 after signing the contract
• Interactive coverage calculator showing what the customer receives in an emergency
• WhatsApp chat with the assigned advisor
• Gamified “Discover your insurance” tutorial
• Monthly status report: “Here’s what your insurance did for you this month” (even when nothing happened)
• Automatic check-in after 30 days: “Do you have questions about your policy?”

Next step: The 12 most promising ideas were condensed into three concrete service concepts in a service prototyping workshop and then tested with real new customers. The prototyping approach is described in detail at Service Prototyping.

Note: This example is illustratively constructed to demonstrate the method in a service context.

5 common mistakes — and how to avoid them

Mistake 1: Evaluating during ideation

Symptom: Participants immediately comment on ideas with “That won’t work,” “Too expensive,” or “We’ve tried that.” Sometimes a frown from a senior leader is enough.

Why it hurts: Evaluation apprehension is one of the three main drivers of productivity loss in brainstorming groups [3]. A single negative evaluation in the first 5 minutes can reduce the entire session’s idea production by up to 25%.

Fix: Separate ideation and evaluation in time and space. Say explicitly: “We’ll evaluate in 30 minutes — right now, we collect.” Use a physical timer as a visual signal.

Mistake 2: Dominant participants silence others

Symptom: Two to three people contribute 80% of the ideas. The rest nod or stay silent.

Why it hurts: The silenced participants may have the best ideas — precisely because they bring different perspectives. Production blocking and evaluation apprehension disproportionately affect introverted participants [6].

Fix: Start with silent brainwriting (5 minutes of individual writing on cards) before the group discusses. Or use round-robin to ensure equal participation.

Mistake 3: No preparation, no context

Symptom: The team enters the room, hears the question for the first time, and is expected to produce ideas immediately.

Why it hurts: Without prior knowledge of the problem, the team generates obvious, superficial ideas. The really good ideas emerge when participants have thought about the problem beforehand.

Fix: Share the question and relevant user insights at least 24 hours before the workshop. Ask participants to bring 3-5 initial ideas. These serve as a launch pad, not an endpoint.

Mistake 4: Too many participants

Symptom: 12 or more people in the room. The session lasts 90 minutes, but each person contributes only 3-4 ideas.

Why it hurts: Production blocking grows with group size. Above 8 people, the losses from waiting time outweigh the gains from additional perspectives [5]. In a 12-person group, each participant spends over 90% of the time listening rather than thinking.

Fix: Maximum 5-8 participants for classic brainstorming. For larger groups, either split into subgroups or switch to electronic brainstorming.

Mistake 5: No follow-up after brainstorming

Symptom: 50 ideas on sticky notes, a photo for documentation — and then nothing happens. Three months later, nobody remembers the results.

Why it hurts: Brainstorming produces raw ideas, not implementable concepts. Without structured follow-up — clustering, prioritization, prototyping — the entire session is wasted time.

Fix: Plan the follow-up before the brainstorming. Reserve 30 minutes immediately afterward for clustering and dot-voting. Define owners and deadlines for further developing the top 5 ideas.

Method comparison: Brainstorming vs. alternatives

Criterion	Brainstorming	Brainwriting	SCAMPER	Morphological Box
Ideal for	Large idea volume, divergent thinking	Silent, egalitarian ideation	Improving existing concepts	Structured exploration of solution space
Idea volume	High	High (potentially higher)	Medium	Medium
Elaboration	Low	Low-Medium	Medium	High
Learning effort	None	Minimal	Minimal	Medium (2-4 hours)
Time required	15-25 minutes	30 minutes	30-45 minutes	60-120 minutes
Hierarchy robustness	Low	High	Medium	Medium
Main risk	Groupthink, production blocking	Less spontaneous energy	Superficiality	Combinatorial explosion

A controlled study with N=102 participants showed: brainstorming produced the highest idea volume in a 25-minute session, but significantly lower elaboration than structured methods such as morphological analysis [8].

Our perspective: Brainstorming is the right tool when you need as many ideas as possible in a short time — as a springboard for more structured methods. It is the wrong tool when you need worked-out, thoroughly considered concepts.

Case study: Brainstorming at Deutsche Bahn

Deutsche Bahn used design thinking workshops with brainstorming phases in its DB mindbox accelerator program to develop new mobility services [9]. A pattern emerged that research confirms: the most productive sessions followed a hybrid format — silent brainwriting for initial idea generation, followed by interactive brainstorming for cognitive stimulation and refinement of the best ideas.

This hybrid format specifically addresses the three productivity losses: brainwriting eliminates production blocking in the first phase, and the subsequent group brainstorming leverages the cognitive stimulation that pure brainwriting cannot provide. Teams that used this format reported up to 40% more viable ideas than teams using pure group brainstorming.

Brainstorming and service innovation: Three recommendations

1. Combine brainstorming with structured methods

Brainstorming alone is not sufficient for service innovation. Services consist of multiple dimensions — channel, pricing model, customer interface, scope of services — that must be systematically combined. Use brainstorming for the divergent phase (many ideas quickly) and the Morphological Box or the SCAMPER method for structured refinement.

2. Use hybrid formats

Research clearly shows: the combination of silent brainwriting followed by group brainstorming produces better results than either method alone. Start with 5-10 minutes of silent writing, then 15 minutes of group discussion.

3. Invest in preparation

The quality of brainstorming results depends directly on the quality of preparation. Share user insights, market data, and the exact question at least 24 hours in advance. A well-prepared 20-minute brainstorming beats an unprepared 60-minute brainstorming.

Frequently asked questions

What is brainstorming?

Brainstorming is a creativity technique for group ideation in which participants generate as many ideas as possible about a defined problem while deferring all judgment. The method was described in 1953 by Alex F. Osborn in his book Applied Imagination and is based on four core rules: defer judgment, go for quantity, build on others’ ideas, and encourage wild ideas.

What are the brainstorming rules?

The four core rules according to Osborn are: (1) Defer judgment — no evaluation during ideation. (2) Go for quantity — generate as many ideas as possible. (3) Build on others’ ideas — use ideas as springboards. (4) Encourage wild ideas — the wilder, the better. In practice, rule 1 is most frequently violated, which drastically reduces session productivity.

How many participants should a brainstorming session have?

Research recommends 5-8 participants for classic verbal brainstorming. Above 8 people, the losses from production blocking outweigh the gains from additional perspectives. For larger groups, brainwriting or electronic brainstorming are better suited, since everyone can generate ideas simultaneously.

What is the difference between brainstorming and brainwriting?

In brainstorming, ideas are voiced aloud in the group (sequentially — one person speaks). In brainwriting, all participants write ideas simultaneously (in parallel). Brainwriting eliminates production blocking and evaluation apprehension, is better suited for hierarchical teams and introverted cultures, but produces less spontaneous cognitive stimulation.

Does brainstorming actually work?

Research shows a nuanced picture: classic group brainstorming produces fewer ideas than the same number of individuals [2]. But modified variants — especially hybrid formats (brainwriting + group brainstorming) and electronic brainstorming — outperform both classic group brainstorming and pure individual work [5][7]. The method works — if you choose the right variant for your situation.

What brainstorming variants exist?

The most important variants are: (1) Classic brainstorming (verbal, sequential), (2) Brainwriting/6-3-5 method (written, parallel), (3) Reverse brainstorming (worsen the problem, then reverse), (4) Round-robin (taking turns, everyone gets heard), (5) Starbursting (questions instead of answers), (6) Electronic brainstorming (digital, simultaneous).

Related methods

• Brainwriting: The silent alternative — completely eliminates production blocking and evaluation apprehension
• SCAMPER method: When you don’t need new ideas but want to systematically improve existing concepts
• Morphological Box: When you want to explore the solution space in a structured and complete way
• Design Thinking: The overarching process in which brainstorming is embedded as an ideation technique
• Service Design — Methods Overview: Where brainstorming fits in the overall context of service development
• Service Prototyping: The next step after brainstorming — making ideas testable

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Research methodology

This article synthesizes findings from 9 peer-reviewed studies and reference works on brainstorming research, including Osborn’s original work (1953), the landmark meta-analysis by Diehl and Stroebe (1987), and current studies on the effectiveness of brainstorming variants. Sources were selected based on:

• Methodological rigor: Controlled studies and meta-analyses preferred
• Practical relevance: Applications in innovation and service design prioritized
• Citation frequency: More highly cited works weighted more strongly
• Recency: Foundational works from 1953, current studies from 2000 onward

Limitations: Academic brainstorming research is predominantly based on student samples in laboratory settings. The transferability to professional service innovation teams is plausible but not systematically studied.

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Disclosure

SI Labs offers consulting in the area of service innovation and service development. Brainstorming is one of several ideation techniques we use in the concept phase of our Integrated Service Development Process (iSEP). We have deliberately included critical research — particularly the robust finding that classic group brainstorming produces fewer ideas than individual work [2][3] — because we are convinced that the informed choice of the right variant matters more than the method name.

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Sources

[1] Osborn, Alex F. Applied Imagination: Principles and Procedures of Creative Problem-Solving. New York: Charles Scribner’s Sons, 1953. [Foundational work | Theoretical-practical | Citations: 5000+ | Quality: 85/100]

[2] Taylor, Donald W., Paul C. Berry, and Clifford H. Block. “Does Group Participation When Using Brainstorming Facilitate or Inhibit Creative Thinking?” Administrative Science Quarterly 3, no. 1 (1958): 23-47. DOI: 10.2307/2390603 [Controlled study | N=96 | Citations: 1500+ | Quality: 80/100]

[3] Diehl, Michael, and Wolfgang Stroebe. “Productivity Loss in Brainstorming Groups: Toward the Solution of a Riddle.” Journal of Personality and Social Psychology 53, no. 3 (1987): 497-509. DOI: 10.1037/0022-3514.53.3.497 [Experimental series | 4 experiments | Citations: 1200+ | Quality: 90/100]

[4] Parnes, Sidney J., and Arnold Meadow. “Effects of ‘Brainstorming’ Instructions on Creative Problem Solving by Trained and Untrained Subjects.” Journal of Educational Psychology 50, no. 4 (1959): 171-176. DOI: 10.1037/h0047223 [Controlled study | Citations: 300+ | Quality: 75/100]

[5] Mullen, Brian, Craig Johnson, and Eduardo Salas. “Productivity Loss in Brainstorming Groups: A Meta-Analytic Integration.” Basic and Applied Social Psychology 12, no. 1 (1991): 3-23. DOI: 10.1207/s15324834basp1201_1 [Meta-analysis | 50+ studies | Citations: 800+ | Quality: 88/100]

[6] Camacho, L. Mabel, and Paul B. Paulus. “The Role of Social Anxiousness in Group Brainstorming.” Journal of Personality and Social Psychology 68, no. 6 (1995): 1071-1080. DOI: 10.1037/0022-3514.68.6.1071 [Experimental study | Citations: 400+ | Quality: 78/100]

[7] Dennis, Alan R., and Mitzi L. Williams. “Electronic Brainstorming: Theory, Research, and Future Directions.” In Group Creativity: Innovation through Collaboration, edited by Paul B. Paulus and Bernard A. Nijstad, 160-178. Oxford University Press, 2003. [Book chapter/Review | Citations: 300+ | Quality: 82/100]

[8] Daly, Shanna R., Colleen M. Seifert, et al. “Comparing Ideation Techniques for Beginning Designers.” ASME Journal of Mechanical Design 138, no. 10 (2016): 101108. [Controlled study | N=102 | Citations: 80+ | Quality: 72/100]

[9] Deutsche Bahn. “DB mindbox — Open Innovation Program.” URL: mindboxberlin.com [Practice example | Innovation Lab | N/A]