Although Dr. William Grey Walter is most known for his Turtle robots, he is a neurophysiologist first. So it's better to study his researches in fields of neural system before we move on to his studies in robots. I found wiki lists two chapters for Dr. W.Grey Walter: Brain Waves and Robots. Here I will add other materials from the google.

He is regarded as the pioneer of cybernetics. So we need to check up more about cybernetics. In 1948, Norbert Wiener described cybernetics as “the scientific study of control and communication in the animal and the machine.” Another interesting thing is that a core concept of cybernetics is self replication, came from von Neumann's cellular automata.

Dr. W.Grey was born in Kansas City, Missouri, in 1910. He's educated mostly in Britain. He made a self-introduction in the book titled “Discussions on Child Development” from which we can see how he was influenced by the Pavlovian Theories in his early studies. Dr. W.Grey carried out long time researches to improve the technologies of electroencephalography(EEG), or the brain waves, for measuring electrical activity in the brain. During this period, he “devoted a number of years to the study of organic lesions of the nervous system, to relearn neuroanatomy and apply it to” some studies. By these efforts, he made some important discoveries about the high speed alpha waves and slow delta waves. He also demonstrated the use of delta waves to locate brain tumors.

Also in this book, Dr. W.Grey described the children project he was engaged in before. From that time, he combined his interests in the physiology of nervous system to the influence of environment on children and how children grew up. Later he extended this “nervous system/environment influence/children development” studies to further thinking. He wrote “and I have attempted particularly to quantify methods of study, to develop men and machines able to make objective and concrete appreciation of the problems which we encounter in this sort of work”. This would lead to our cybernetics scientist Dr. Grey.

In 1951, Dr. Grey displayed his `tortoises' at the Festival of Britain. These robots were designed to show the interaction of two sensory systems: a light-sensitive and a touch-sensitive control mechanisms. In effect, this simulated two nerve cells with visual and tactile inputs. These systems interacted with the motor drive in such a way that the `turtles' exhibited some 'behaviour', like finding their way round obstacles.

Although the original intention was to study the basis of simple reflex actions and to test his theory on complex behavior arising from neural interconnections, Dr. Grey's successful experiments with these robots had great influences on the birth of science of cybernetics. His two papers, “An Imitation of Life” in 1950, “A Machine that Learns” in 1951 and his book “The Living Brain” in 1963 were widely read and studied.