Continuing with the diffusion model from Chapter $19,$ recall that the threshold q was

derived from a coordination game that each node plays with each of its neighbors.

Specifically, if nodes v and w are each trying to decide whether to choose behaviors A

and B$,$ then:

$$ if v and w both adopt behavior A$,$ they each get a payoff of a $>0$;

$$ if they both adopt B$,$ they each get a payoff of b $>0$; and

$$ if they adopt opposite behaviors, they each get a payoff of $0.$