  Threshold models and their dynamics may be used to model the spread of
`behaviors' in social networks. Regarding such from a modal logical
perspective, it is shown how standard update mechanisms may be emulated using
action models -- graphs encoding agents' decision rules. A small class of
action models capturing the possible sets of decision rules suitable for
threshold models is identified, and shown to include models characterizing
best-response dynamics of both coordination and anti-coordination games played
on graphs.
