Grey Walter's most famous work was his construction of some of the first electronic autonomous robots. He wanted to prove that rich connections between a small number of brain cells could give rise to very complex behaviors - essentially that the secret of how the brain worked lay in how it was wired up. His first robots, which he used to call Machina speculatrix and named Elmer and Elsie, were constructed between 1948 and 1949 and were often described as tortoises due to their shape and slow rate of movement - and because they 'taught us' about the secrets of organisation and life. The three-wheeled tortoise robots were capable of phototaxis, by which they could find their way to a recharging station when they ran low on battery power.

In one experiment he placed a light on the "nose" of a tortoise and watched as the robot observed itself in a mirror. "It began flickering," he wrote. "Twittering, and jigging like a clumsy Narcissus." Walter argued that if it were seen in an animal it "might be accepted as evidence of some degree of self-awareness."