Completion and Persistence

Completion and Persistence are two very important properties of CAs
Completion is the ability of a CA to ignite many neurons even though only a few neurons are directly activated by environment
This is necessary to, for instance, know a cat has a tail even though you don't see it
Persistence is the ability of the CA to remain active after stimulus has ceased
Importantly, a simple measurement can be used to give a strong indication of both of these: Pearson's Product Correlation
Hetherington used this measurement to compare different nets
For completion, to variants of a pattern are presented, and after (say) 20 cycles, both nets should have a similar activity pattern
For persistence, the same net after (say) 20 and 50 cycles should be highly correlated
Of the nets we've shown above, many are quite good at completion
Most also remain persististant indefinitely