To be able to send messages, an agent needs to receive a kind of “stimulation currency” from others.
In the film, the agents stay invisible – only their messages are colourfully visualised.
In this image, each white circle represents an agent, and the size indicates its capability to send messages.
A sends a message to B, then B can send a message to either A or C – it’s a set of very simple rules which determine the behaviour of the agents – and it seems like a very dry simulation of human communication.