II
When some years ago, the American public was confronted with the striking exhibitions of muscle-reading, the wildest speculations were indulged in regarding its true modus operandi; and the suggestion that all that was done was explicable by the skillful interpretation of the unconscious indications given by the subjects, was scouted or even ridiculed. It was not supposed that such indications were sufficiently definite for the purposes of the "mind-reader," or were obtainable under the conditions of his tests. Again, it was urged that this explanation was hardly applicable to certain striking performances, which in reality involved other and subtler modes of thought-interpretation, and the accounts of which were also exaggerated and distorted. And furthermore, it was argued, too many worthy and learned persons were absolutely certain that they had given no indications whatever. For a time the view that mind-reading was muscle-reading rested upon rather indirect evidence, and upon a form of argument that carries more weight with those familiar with the nature of scientific problems than with the public at large. But the development of experimental research in the domain of psychology has made possible a variety of demonstrations of the truth and adequacy of this explanation. It was with the purpose of securing a visible record of certain types of involuntary movements, that the investigation, the results of which are here presented, was undertaken.
Fig. 1.—The automatograph. When in use a screen (not shown in the illustration) cuts off the view of the apparatus from the subject. The recording device, which may also be used separately, is shown in outline in half its full size. R is a glass rod which moves freely up and down in the glass tube T, which is set into the cork C. A rubber band B is provided to prevent the rod from falling through the tube, when not resting upon the recording-plate.
Inasmuch as the movements in question are often very slight, somewhat delicate apparatus is required to secure their record; the apparatus must in a measure exaggerate the tendency to motion though without altering its nature. The form of apparatus which I devised for this study, and which may be appropriately called an automatograph, is illustrated in the accompanying figure (p. 310). It consists of a wooden frame, enclosing a heavy piece of plate glass (fifteen inches square), and mounted upon three legs which are provided with screw adjustments for bringing the plate into a perfect level. Upon the plate of glass are placed in the form of a triangle three well turned and polished steel or brass balls; and upon the balls rests a thin crystal-plate glass set in a light wooden frame. The finger-tips of one hand rest upon the upper plate in the position indicated. When all is properly adjusted and glass and balls are rubbed smooth with oil, it is quite impossible to hold the apparatus perfectly still for more than a few seconds; the slightest unsteadiness or movement of the hand at once sets the plate rolling with an irregular motion. If one closes the eyes and fixes the attention upon a definite mental image or train of thought, it is easy to form the conviction that the plate remains quiet, but the record proves that this is not the case. The other parts of the apparatus are designed to give a record of the movements of the plate. Fastened to the light frame containing the upper glass plate is a slender rod some ten inches long, bearing at its end a cork; and piercing the cork is a small glass tube within which a snugly fitting glass rod has room to move. The rod is drawn to a smooth, round point; and when in position rests upon a piece of glazed paper that has been blackened over a flame and then smoothly stretched over a small glass plate. The point of the rod thus records easily and accurately every movement of the hand that is imparted to the upper plate, and by the manner of its adjustment accommodates itself to all irregularities of movement or recording surface. This recording device is shown in greater detail in the illustration, and was used to good advantage as a simple automatograph in independence of the balls and plates. In that case the recording part is held in the hand as though it were a pencil, but in a vertical position, and the record plate may be placed upon a table; or for special purposes the plate may be held in the other hand or fastened to the top of one's head. When not otherwise stated, the records here reproduced were obtained by use of the automatograph. Some of the records are noted as having been secured with the simpler device just described.
The process of securing a record is as follows: the subject, standing, places his hand upon the automatograph, with the arm nearly horizontal and not quite fully extended, and the elbow bent in a fairly comfortable posture; his attention is engaged by asking him to listen to and count the strokes of a metronome; to look at and count the oscillations of a pendulum; to read from a book; to call out the names of colors; to think of a given direction or locality, or the position of an object; and so on. He is instructed to think as little as possible of his hand, making a reasonable effort to keep it from moving. To cut off the apparatus from the subject's field of vision and attention, a large screen is interposed between him and the record, a curtain with a suitable opening for the arm forming part of the screen. The operator holds the glass pencil in his hand, and when all is in readiness allows it to slip through the glass tube and begin to write, removing it again after a definite interval or when the record seems completed.