Emergence of Functional Hierarchy in a Multiple Timescale Neural Network Model: A Humanoid Robot Experiment
Figure 8
Primitive representations in fast context units before and after additional training.
Changes of context activation during each movement before and after additional training are visualized in a 2 dimensional space based on the results of PCA analysis (plotted only for position 3). The four graphs on the left side and two graphs on the right side correspond to representations before and after additional training, respectively. The first and second movements in the novel sequences learned through additional training are colored red (UD and BF) and green (LR and Touch), respectively. The structure of representations corresponding to each primitive were preserved even after additional training, indicating that motor primitives were represented in dynamics of fast context units, with novel behavior sequences constructed out of combinations of these primitives. UD: up-down, LR: left-right, BF: backward-forward and Touch: touch with single hand behavior.