[E]xperiments with a simple little machine, designed to mimic certain elementary features of animal behavior... Consisting only of two vacuum tubes, … - William Grey Walter

Some of these patterns of performance were calculable, though only as types of behaviour, in advance; some were quite unforeseen.

The first notion of constructing a free goal-seeking mechanism goes back a wartime talk with the psychologist, , whose untimely death was one of the greatest losses Cambridge has suffered in years. When he was engaged on a warjob for the Government, he came to get the help of an automatic analyzer with some very complicated curves he had obtained, curves relating to the aiming errors of air gunners. Goal-seeking missiles were literally much in the air in those days; so, in our minds, were scanning mechanisms. Long before the home study was turned into a workshop, the two ideas, goal-seeking and scanning, had combined as the essential mechanical conception of a working model that would behave like a very simple animal.

[Walter even gave the tortoises a mock-biological name, Machina speculatrix] because they illustrate particularly the exploratory, speculative behaviour that is so characteristic of most animals.