The Story of the Mind

by James Mark Baldwin

A great many laboratories have now been established in connection with the universities in Germany, France, and the United States. They differ very much from one another, but their common purpose is so to experiment upon the mind, through changes in the stimulations to which the individual is subjected, that tests may be made of his sensations, his ability to remember, the exactness and kind of movements, etc.

The working of these laboratories and the sort of research carried out in them may be illustrated best, perhaps, by a description of some of the results, apparatus, methods, etc., employed in my own laboratory during the past year. The end in view will, I trust, be considered sufficient justification for the degree of personal reference which this occasions; since greater concreteness and reality attach to definite descriptions such as this. The other laboratories, as those at Harvard and Columbia Universities, take up similar problems by similar methods. I shall therefore go on to describe some recent work in the Princeton laboratory.

Of the problems taken up in the laboratory, certain ones may be selected for somewhat detailed explanation, since they are from widely different spheres and illustrate different methods of procedure.

I. Experiments on the Temperature Sense.—For a score of years it has been suspected that we have a distinct sense, with a nerve apparatus of its own, for the feeling of different temperatures on the skin. Certain investigators found that this was probably true; it is proved by the fact that certain drugs alter the sensibility of the skin to hot and cold stimulations.

Another advance was made when it was found that sensations of either hot or cold may be had from regions which are insensible at the same time to the other sort of stimulation, cold or hot. Certain minute points were discovered which report cold when touched with a cold point, but give no feeling from a hot object; while other points would respond only with a sensation from heat, never giving cold. It was concluded that we have two temperature senses, one for hot and the other for cold.

Taking the problem at this point, Mr. C.[3] wished to define more closely the relation of the two sorts of sensation to each other, and thought he could do so by a method by which he might repeat the stimulation of a series of exact spots, very minute points on the skin, over and over again, thus securing a number of records of the results for both hot and cold over a given area. He chose an area of skin on the forearm, shaved it carefully, and proceeded to explore it with the smallest points of metals which could be drawn along the skin without pricking or tearing. These points were attached to metallic cylinders, and around the cylinders rubber bands were placed; the cylinders were then thrust in hot or cold water kept at certain regular temperatures, and lifted by the rubber bands. They were placed point down, with equal pressure, upon the points of the skin in the area chosen. In this way, points which responded only to hot, and also those responding only to cold, were found, marked with delicate ink marks in each case, until the whole area was explored and marked in different colours. This had often been done before. It remained to devise a way of keeping these records, so that the markings might all be removed from the skin, and new explorations made over the same surface. This was necessary in order to see whether the results secured were always the same. The theory that there were certain nervous endings in the skin corresponding to the little points required that each spot should be in exactly the same place whenever the experiment was repeated.

[3] Mr. J. F. Crawford, graduate student.

Mr. C. made a number of so-called "transparent transfer frames." They are rectangular pieces of cardboard, with windows cut in them. The windows are covered with thin architect's paper, which is very transparent. This frame is put over the forearm in such a way that the paper in the window comes over the markings made on the arm. The markings show through very clearly, and the points are copied on the paper. Then certain boundary marks at the corners are made, both on the paper and on the arm, at exactly the same places, the frame is removed, and all the markings on the arm are erased except the boundary points. The result is that at any time the frames can be put over the arm again by matching the boundary points, and then the original temperature spots on the skin will be shown by the markings on the paper window.

Proceeding to repeat the exploration of the same area in this way, Mr. C makes records of many groupings of points for both hot and cold sensations on the same area; he then puts the frames one upon another, holds them up before a window so that they have a bright background, and is thus able to see at a glance how nearly the results of the different sittings correspond.

His results, put very briefly, fail to confirm the theory that the sense of temperature has an apparatus of fixed spots for heat and other fixed spots for cold. For when he puts the different markings for heat together he finds that the spots are not the same, but that those of one frame fall between those of another, and if several are put together the points fill up a greater or smaller area. The same for the cold spots; they fill a continuous area. He finds, however, as other investigators have found, that the heat areas are generally in large measure separate from the cold areas, only to a certain extent overlapping here and there, and also that there are regions of the skin where we have very little sense of either sort of temperature.