WARD C. HALSTEAD Departments of Psychology and of Medicine, University of Chicago
It is apparent to members of this symposium that the task of relating behavior and brain functions is indeed a formidable one. I should prefer to think that this is especially true for the class of behaviors known as intellect in man. But it seems that it is also true for the simplest unit of ordered behavior recognized by psychologists. As long ago as 1912, Yerkes (36) reported that he was able to train the lowly earthworm to form a direction habit in exiting from one arm of a T-maze. The left arm of the maze contained at its entrance a strip of sandpaper which signaled the presence of an electric grill, located just beyond. The other arm of the maze opened directly on a dark, moist environment. Yerkes started his worms at the base of the T several inches from the choice point. He found that the habit of turning toward the right arm of the T-maze (thus avoiding the grill) appeared in twenty to one hundred trials. A three-week rest period yielded no loss of the habit. Surgical removal of the cephalic ganglions or "brain" of the earthworm did not destroy the habit. In fact, the anencephalic worms performed quite well until the anterior segments began to regenerate. With the coming of a new "brain" the habit degenerated. Where were the traces of the habit during the interval between the first and second brain?
A satisfactory answer to one form or another of this question has commanded the interest of a considerable segment of biological science during the last half century. Some of us are not impressed by the progress that has so far been made in our respective disciplines towards finding an answer which will account for the behavior of Yerkes' earthworms. I can only ask your indulgence as I discuss somewhat analogous problems as they arise at the level of man.
It is virtually impossible to date accurately the beginnings of our topic. According to the late Professor Henry Breasted (4), the term "brain" is recorded for the first time in human speech in the Edwin Smith Surgical Papyrus, which was transcribed about 1700 B.C.