Figure 8.

Parametric and behavioural variation. We show the number of episodes until the emergence of gesturing behaviour in C, as a function of parameter values in M's action-recognition module. The connection weights between M's mirror system and her goal neurons are updated by a constant, which we vary here. The threshold for these neurons to signal distal goal change in M, and a new action policy, is also varied here. Enlarged graph symbols (see inset) indicate the episode (x-axis) at which C began gesturing to M. These and other parameter value shifts result in varied patterns of behaviour between M and child. The y-axis represents the within-episode time duration; we normalize this because episodes where the child can gesture are much quicker than episodes where he must first walk, then reach, towards the mother in service of his goal. As can be seen, ontogenetic ritualization reduces time to completion by more than half.