There is a particular kind of meeting that feels productive while it is happening and yields almost nothing afterward. Someone books a room, writes IDEAS across the top of a whiteboard, and asks everyone to call things out. People do. There is energy, laughter, a marker squeaking, a wall slowly filling with sticky notes. Everyone leaves feeling creative. Then a week later you look at the photo of that wall and realize most of it was obvious, half of it repeats, and the one idea you actually shipped came from a Slack message someone sent the next morning.
The instinct is to blame the people — not creative enough, not prepared, too junior, too quiet. But the more uncomfortable finding from decades of research is that the format itself is the problem. Putting a group of people in a room and asking them to generate ideas out loud, together, reliably produces fewer and worse ideas than the same people would have produced sitting alone. The mechanism has a name, and once you see it you cannot unsee it in any brainstorm you sit through.
The experiment that should have ended the brainstorm
When advertising executive Alex Osborn popularized brainstorming in the 1950s, his claim was bold: a group, freed from criticism and encouraged to riff, would generate far more ideas than its members could alone. It is an appealing story, and it spread everywhere. The trouble is that when psychologists actually tested it, the opposite kept happening.
The standard design is elegant. Take a creative task — uses for an object, names for a product, ways to solve some open problem. Run it two ways. In one condition, four people brainstorm together as a real, talking group. In the other, four people work alone in separate rooms, and afterward you pool their ideas and remove any duplicates. That second arrangement is called a nominal group — a group in name only, because the people never interact.
Across study after study, the nominal groups win, and not by a little. Four people thinking separately generate substantially more ideas — and more good ideas, judged blind — than four people thinking together. The interacting group, the one that feels collaborative and alive, is the one that underperforms. This result is robust enough that researchers have spent more energy explaining why it happens than debating whether it does.
Production blocking: you can only speak one at a time
In the 1980s, the psychologists Michael Diehl and Wolfgang Stroebe set out to find the culprit. There were several suspects. Evaluation apprehension — the quiet fear of saying something stupid in front of colleagues. Social loafing — the tendency to coast when individual effort is invisible inside a group's output. Both are real, and both shave something off a group's performance.
But when Diehl and Stroebe carefully separated the causes, the largest one turned out to be almost mechanical, and almost obvious in hindsight: in a conversation, only one person can talk at a time. They called it production blocking.
Think about what your mind is doing while someone else is speaking. You had an idea. You can't say it yet — Priya is mid-sentence. So you hold it. To hold it, you rehearse it silently, which means you are no longer listening closely to Priya, which means you may miss the thread that would have sparked your next idea. Or you keep listening, and by the time the floor opens your idea has faded, or it now feels redundant, or the conversation has moved three topics downstream and the moment has passed. Either way, an idea that existed is gone.
Multiply that by everyone in the room, every time anyone speaks, for an hour. The verbal channel is a single lane, and ideas arrive in parallel. The queue is where they die. People working alone never queue — they capture every thought the instant they have it, in whatever order it arrives, without waiting for a turn or worrying that it sounds like what Priya just said.
What makes production blocking so insidious is that it is invisible from inside the room. You don't experience the ideas you lost. You only experience the lively discussion you had, which feels like evidence that the meeting worked.
Why the room feels good anyway
If interacting groups produce less, why does everyone enjoy them more and rate them as more productive? This is one of the strangest parts of the literature: members of real brainstorming groups consistently feel they performed better than they did, and better than the people who worked alone.
Part of it is the warmth of building on each other — the social pleasure of a riff landing, of someone laughing at your suggestion. Part of it is a subtle accounting error. In a group, you hear every idea spoken aloud, so the total feels large and shared; you take partial credit for the collective pile. Alone, you only have your own modest list and no applause. The group simply feels more generative, and that feeling is what gets the next brainstorm booked. The format survives not because it works but because it is pleasant, and we mistake the pleasantness for output.
There is a quieter cost layered on top. The first few ideas spoken in a group tend to set the direction, and subsequent thinking clusters around them — a kind of anchoring. So the group doesn't just produce fewer ideas; it produces ideas that are more similar to one another, exploring a narrower slice of the possibility space. Solitary thinkers, never anchored to a shared opening, wander further apart, which is exactly what you want when you are hunting for something genuinely new.
The fix is structural, not motivational
The useful thing about production blocking is that, because it is mechanical, it has a mechanical fix. You do not need more creative people or a better facilitator or a cleverer prompt. You need to remove the single-lane bottleneck so ideas don't have to wait in line.
The simplest version is brainwriting. Before anyone speaks, everyone writes — silently, in parallel, for five or ten minutes — putting down as many ideas as they can on their own. No turns, no queue, no waiting. Now every channel is open at once and nothing is lost to rehearsal. Then you come together, pool the lists, remove duplicates, and use the discussion for what groups are genuinely good at: combining, challenging, and selecting from ideas that already exist on paper.
This sequence — diverge alone, converge together — respects what each mode does well. Solitary generation maximizes the volume and variety of raw material. Group discussion is poor at producing ideas but excellent at evaluating them, spotting flaws, and merging two half-formed thoughts into one good one. Most brainstorms fail because they ask the group to do the one thing groups are worst at, and skip the one thing groups are best at.
A few details make it work. Collect the written ideas before discussion starts, so the loudest or most senior voice can't anchor the room. Keep the silent round genuinely silent — no "just call out anything as it comes," which quietly reopens the bottleneck. And judge ideas later, in a separate pass, so the fear of immediate reaction doesn't suppress the strange suggestion that turns out to be the good one.
What the wall of sticky notes was really telling you
The next time you leave a brainstorm feeling energized but empty-handed, resist the urge to blame the room's creativity. Ask instead how many ideas never got spoken — held in someone's head until the turn came and the thought was gone. That invisible pile is usually larger than the one on the wall, and it is the format, not the people, that buried it.
The deeper lesson generalizes past brainstorming: a lot of what we call a "bad meeting" is a good group fighting a bad structure. The energy is real, the intentions are real, the talent is in the room — and the design quietly wastes all three. You can't feel that waste while it's happening, which is exactly why it persists meeting after meeting.
That blind spot is the reason we built meetingmortem — a way to run a quick post-mortem on your meetings so the patterns that don't announce themselves, like production blocking, stop costing you in silence. It turns the vague sense that that could have been an email, or a doc, or ten quiet minutes into something you can actually see and fix. If your best ideas keep dying in the queue, it's worth a look: https://meetingmortem.lumenlabs.works