The Seven-Person Threshold
Every person added to a meeting beyond seven reduces decision quality by roughly 10%. Not because of introversion. Because of math.
With five people in a room, there are 10 possible communication links. With seven, there are 21. With ten, there are 45. Every additional person doesn't add linearly to the conversation. They multiply the coordination overhead exponentially.
Bain research found that each person beyond seven in a decision-making meeting reduces effectiveness by approximately 10%. At 17 people, the probability of making an effective decision approaches zero.
The mechanism isn't about introversion or meeting culture. It's about diffusion of responsibility. As groups grow, individual accountability drops. People assume someone else will raise the concern, do the analysis, or push back. The Ringelmann Effect, first documented in 1913, showed that individuals exert less effort as group size increases. Over a century later, we're still ignoring it.
The nudge: Find your next meeting with more than seven attendees. Split the invite list into "deciders" (people whose input changes the outcome) and "informed" (people who need the result). Run the meeting with deciders only. Send a three-sentence summary to the rest. Most will thank you.
