The construction of systems that reproduce organismic behaviour — in hardware or software, as pre-wired or growth models.
Young surveys the famous hardware models — maze-runners, light-followers, Grey Walter's tortoise ELMER — having warned against over-reading their lifelike behaviour.
George distinguishes pre-wired models (a programmed computer) from growth models (organic, structure-changing), arguing they are complementary, and records the migration from hardware to software.