“Dunbar’s number” is a theoretical cognitive limit on the number of stable social relationships humans can maintain at one time. According to Robin Dunbar, a British anthropologist, humans have the cognitive capacity to keep track of somewhere around 150 close personal connections. Beyond this limited circle, we start treating people less like

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My anecdotal evidence generally seems to support the idea that group sizes will usually plateau at a number lower than 150 participants. This comes from 20 years of doing facilitation both on and offline, running several software companies, and running various forums at America Online. In particular, many online communities provide good evidence... See more