Individuals act only once a personal threshold of prior participation is met, so small differences in thresholds produce very different cascades.
Granovetter's 1978 model. A crowd of people with thresholds one to a hundred riots; change one person's threshold and nothing happens at all. Aggregate behaviour is not readable from average disposition.
In practice
- A team with one person who will raise a concern unprompted gets a full discussion; the same team without that person nods the proposal through, and everyone privately doubted it.
- A strike ballot fails by a margin no survey of grievances would have predicted, because what mattered was who would move first.