This is a fascinating question, and I don't think I'm qualified to give an authoritative answer to it, but I think the _primary_ property of brains and brain-li

This is a fascinating question, and I don't think I'm qualified to give an authoritative answer to it, but I think the _primary_ property of brains and brain-like neural complexes is that they encode behavioral responses to stimuli. Similar to how a signal transduction process mediates between molecular receptors on cell membrane and cell behaviors, the neural complex mediates between stimuli and response at the level of the organism. But at the same time I can see why you are thinking about flexibility as some sort of "primary property" because they seem to be inherently flexible in some way. I'm locating _plasticity_ more narrowly to the cortex part of the animal brain, but perhaps the cortex is just an amplification of some simpler lower-level flexibility. At this point my knowledge of the subject falls short. Edit: thank you for the interesting discussion, you have sparked me to dig more deeply into these topics!