Forced moves or good tricks in design space? Landmarks in the evolution of neural mechanisms for action selection

This review considers some important landmarks in animal evolution, asking to what extent specialized action-selection mechanisms play a role in the functional architecture of different nervous system plans, and looking for forced moves or good tricks (see Dennett, D., 1995, Darwin's Dangerous Idea, Penguin Books, London) that could possibly transfer to the design of robot control systems. A key conclusion is that while cnidarians (e.g. jellyfish) appear to have discovered some good tricks for the design of behavior-based control systems-largely lacking specialized selection mechanisms the emergence of bilaterians may have forced the evolution of a central ganglion, or archaic brain, whose main function is to resolve conflicts between peripheral systems. Whilst vertebrates have many interesting selection substrates it is likely that here too the evolution of centralized structures such as the medial reticular formation and the basal ganglia may have been a forced move because of the need to limit connection costs as brains increased in size.