Information Cascade in Social Networks
Threshold model: agents adopt when enough neighbors have adopted
Granovetter's threshold model (1978): each agent has a threshold φ — they adopt the information/behavior
only when the fraction of their neighbors who have already adopted exceeds φ. Even with identical thresholds, outcomes
depend critically on network structure and seed placement.
A global cascade occurs when a small seed triggers adoption across most of the network.
Watts (2002) showed cascades require: (a) a connected component of low-threshold "early adopters," and
(b) seeds placed within it. The cascade window — the range of connectivity where global cascades
are possible — is narrow. Too sparse: cascade dies early. Too dense: each node needs many neighbors to adopt first.
Click New Network to regenerate, then Run to watch the cascade propagate.