Investigating single neurons is somewhat like tracing wires and single transistors to understand the functioning of computers. There are so many and they do so many different things that the task seems overwhelming, especially if we want to go beyond single individuals to hundreds and thousands of species.
Rather than using this bottom-up approach, we suggest a top-down approach. A top-down approach is common in designing and developing large and complex information processing systems.
With a top-down approach we investigate system requirements and constraints as well as abstract high-level architectures that might address the requirements and constraints.
We shall propose a similar approach to investigating organically-based information processing without worrying precisely how the high-level design is realized with nature's equivalent of hardware and software.
Computer-based information processing uses standard processes such as storage and retrieval or calculations. In the next chapter we look for basic processes for evolution that might reappear in nature's organic information processing.