The World of Touch

David Katz, Lester E. Krueger, Lester E. Krueger, Lester E. Krueger, Lester E. Krueger

• Publisher: Psychology Press
• Year: 2013
• Print ISBN: 9780805805291
• eBook ISBN: 9781134752577
• Topic: Psychology
• Subtopic: Cognitive Psychology & Cognition
• Index: Psychology

For the first time, David Katz's classic monograph The World of Touch has been translated into English. Regarded as one of the premiere experimental psychologists, Katz vigorously opposed the atomism and "tachistoscopic" mentality typical of the sensory psychology of his day.

In The World of Touch, Katz sought to dispel the invidious distinction between the supposedly higher (e.g., vision, audition) and lower (e.g., touch) senses. To help touch regain its original prominence in the field, Katz demonstrated, through very simple, yet creative experiments, how fascinating the abilities of touch are, and how valuable the tactual stimulus can be in specifying objects, surfaces, substances, and events. In addition, Katz emphasized the importance of higher-order invariants in the perception of objects, and the holistic quality of perception in time as well as space.

DIVISION II:

QUANTITATIVE STUDIES OF THE TACTUAL PERFORMANCE

Chapter I:

Studies on Surface Touch

Part I: Experiments on the Qualities (Modifikationen) of Surface Touch

Section 18. The Tactual Material

First a general caveat: The research reported in Division II will not and cannot be exhaustive. I freely confess that the almost limitless possibilities for varying the experimental conditions has occasionally had a frankly inhibiting effect on my disposition to carry out the studies. Where should one begin, when such rich abundance beckons everywhere! I dare not conclude that the experiments I finally selected were the correct choices; someone else would perhaps have considered others more important. However, I now categorically refuse to indicate everything that could still be undertaken in this area. My experience indicates that providing that type of hint—sometimes kept mysterious to boot—in a footnote inhibits other researchers from taking up the problem.

To set some bounds, the investigation was limited from the beginning to a sufficiently large but not too extensive set of tactual material. All experiments in Part I were carried out with 14 different papers. Obtaining the materials was done somewhat differently than is usual in quantitative studies in psychology. To wit, the tactual stimuli could not be suitably produced for our experimental purposes with precisely stepwise differences (with an exception mentioned below in Section 24, Subsection 4), but rather a suitable selection had to be made from the hundreds of papers normally available. Regrettably, the clarity of the procedure suffers somewhat due to this. I cannot even begin to characterize all of the papers in the sense of commercial product specifications. Verification of the findings is thereby made somewhat more difficult, but not impossible.

I will first describe the series of 14 papers: 1) very smooth, very well waxed paper; 2) smooth, well waxed paper; 3) slightly waxed paper with a slight grain; 4) very fine grained writing paper; 5) fine grained writing paper; 6) smooth paper with a distinct grain; 7) soft paper with a slight roughness; 8) harder, not too rough, drawing paper; 9) soft blotting paper; 10) moderately hard blotting paper; 11) hard grained blotting paper; 12) hard, rough packing paper; 13) very hard, very rough packing paper; 14) soft, extremely rough cloth paper. (The cloth paper was that deep, black type frequently used for visual designs. As is well known, it consists of an approximately .5-mm thick layer of cloth fibers glued on paper. It might be objected here that we are no longer dealing with paper. The series was selected, however, without regard to the chemical-physical properties of the raw materials used, from materials customarily thought of as paper based on their visual and haptic qualities.)

I selected the papers so that by concentrating my attention and touching as I wished, I could distinguish each paper from every other one in the series. Since it was not possible to get around this subjective procedure in devising the series, usable data were assured in the following experiments only from observers who did not deviate too far above or below the experimenter in their tactual sensitivity. The ordering of the papers was such that the farther apart they were on the scale, the more their tactual impression differed in general. Thus, in most cases, adjacent papers had the greatest similarity with each other. The subjects kept their eyes closed when touching. In addition, their ears were stuffed with cotton after it became evident that noises originating from touching could give useful hints for recognizing the properties of the tactual material. However, once alerted to this source of error, many observers said they were not certain that they did not still have auditory impressions of many tactual surfaces in spite of their plugged ears. We will pursue this remarkable statement futher in a different context (Section 39).

Performance naturally fluctuated from person to person in these experiments, as is typical, but for now we must be less concerned with working out the individual differences than determining the general tendencies. The satisfactory agreement in the results presented below indicates that the performance obtained was average or typical.

Section 19. Basic Experiment

The papers on our scale will always be designated below by their numbers (1-14). They were presented on a pasteboard backing, and covered with a piece of cardboard having a rectangular opening, whose prominent edges indicated the boundaries of the paper to the touching hand. The papers were 10 by 15 cm wide, which offered the touch organ wide room for maneuver. In each instance, two papers were presented for comparison, as a rule, in the combinations 1 and 2, 2 and 3, 3 and 4, etc. Thus, 13 pairs were judged. If two adjacent papers on the scale could not be distinguished by the subject, then pairs of papers were presented which differed by 1, 2, 3, or more intervening papers. Insofar as no finer precision was obtained, we will consider as correct a judgment in which two adjacent papers were recognized as different, and as false any judgment which deviates from that. The subjects were instructed to behave as if they had to purchase papers in a store for an important practical purpose, while having to distinguish between the presented papers exclusively by touch. They were free to choose the hand, the fingers of the hand, and the way in which to touch. The temporal order was not prescribed, so the observers could begin with the paper surface lying at the left or right, and they could also return, if it seemed convenient, to the surface which they had touched first. The subjects were kept in the dark in every respect, i.e., they were told nothing about the purpose or the results of the experiment. Though no duration of touching was prescribed, the subjects did not abuse this freedom, but decided relatively rapidly. This confirms what I myself have observed time and again, which is that one has a remarkably fine feeling for whether or not longer touching would aid discrimination or recognition. The subjects were Miss Lommatzsch (L), a philosophy student; Dr. Keller (K); and Mr. Herbers (H), a theology student. L was lefthanded and used her left hand for touching, whereas K and H were righthanded and, as would be expected, touched with their right hands.

Under the experimental conditions as described, L and K correctly distinguished all papers from each other, and H distinguished all except 4, 5, and 6, which appeared the same to him. Although the instructions demanded only the identification of sameness or difference, the subjects often also provided qualitative judgments by speaking of writing paper, blotting paper, drawing paper, etc. I will disregard such judgments for now; experiments will be presented below (Section 23) in which qualitative judgments of the individual papers were requested in the instructions. Some papers feel cool and others warm; later experiments (Section 36) will reveal the interesting role that temperature plays in the recognition of materials. From the results obtained in the basic experiment, it appears that our selection of papers was appropriate; it was intended that all papers would be discriminable from each other under favorable conditions for touching. Essentially the same results were obtained in the basic experiment when the papers of each pair were not touched successively by the same hand, but simultaneously by both hands.

The report below of variations of the basic experiment will be interrupted here and there in order to point out more general findings of the experiments. Accordingly, we will now make a few remarks concerning the touching movement in the basic experiment, which will somewhat sharpen what was said above (Section 17). It is surprising how much difficulty the subjects had in answering when asked which fingers and what method they used in touching. Obtain for yourself a tactual impression from a piece of paper and surrender completely to it. You then will be able to confirm how modest is the degree of consciousness of everything that refers to the movement itself. With which fingers and which portions of the fingers did you touch? How long did you touch until the specific impression of paper occurred? With what speed was the movement carried out as a whole or in parts? To obtain information concerning these and yet other aspects of the movement, one would have to repeat the touching movement, and let the tactual impression itself recede completely into the background in order to make conscious the component contents of movement. Once the specific tactual impression of a paper has been established, it remains completely constant during further touching; it stands out quite sharply from the somewhat chaotic background fashioned by the touching movement. The basic experiment has aided us here in stating questions whose experimental answers will follow below.

Section 20. Variation in the Size of the Tactual Surfaces

In the basic experiment, the tactual surfaces were so large that the observer never felt the need to touch beyond their boundaries. The first variation of the basic experiment involved reducing the size of the tactual surfaces. From the 14 papers on the scale, two sets of disks having diameters of 2 and 4 mm, respectively, were punched out, and each disk was pasted by itself onto a cardboard surface. Then, following the same procedure as in the basic experiment, the disks of each set were presented for touching. Subjects were L and K. L touched with the middle finger of her left hand, which she considered the most sensitive; K used his right index finger. The disks of paper were felt as low elevations of varying height on the background of the cardboard; the experimenter placed the touching fingers onto the correct position, i.e., laid them on the disks.

All of the 4-mm wide tactual surfaces were distinguished from each other by L, just as in the basic experiment, except that 8 was judged the same as 9, and 10 the same as 11. Thus, compared with 13 correct judgments in the basic experiment, there were 11 correct and 2 incorrect judgments here. Whereas most of the larger disks could still be recognized as consisting of paper, this no longer was the case with the smaller disks. Despite this, however, the differences between the individual tactual surfaces could still be distinguished remarkably well. L gave 10 correct and 3 incorrect judgments. K did little worse with the 2-mm wide disks: 8 correct and 5 incorrect judgments. It was most surprising that differences between such small touching surfaces could still be so reliably discerned. Punching out disks of 2-mm diameter produces a somewhat bent-down edge, which may be rougher or smoother than the paper itself, depending upon the type of paper, but as a rule is smoother. If subjects let their judgments be influenced by that edge as well, then that alone may explain the increase in erroneous judgments from the basic experiment (This source of error cannot be eliminated by placing cardboards with openings on the tactual surfaces, and touching the latter through the openings. The touch organ no longer would come into contact with the tactual surfaces in the desired manner.) From this variation of the basic experiment, we establish that even a vast reduction in the size of the tactual surface impairs its discriminability only slightly.

A few spontaneous comments concerning size differences between the small disks seem worth mentioning here. To both L and K, for example, 12 appeared significantly smaller than both 11 and 13. These judgments probably are related to the perceived thickness of the tactual surfaces, with the thicker one appearing to be larger. Otherwise, the difference in paper thickness was unimportant for the results of the experiments. A quite remarkable size illusion occurred for Miss Kretzer (Kr), a philosophy student who occasionally participated in these experiments. Like K, she touched with her right index finger. She reported that the larger disks appeared to have a diameter of 3 to 4 cm. If she had given it some thought, she would not have doubted for an instant that the disks were very much narrower than her touching finger and therefore had to be considerably narrower than 3 to 4 cm. Considerable overestimations of the size of the disks also were typical for the other subjects.

What purpose was served by the variation of the basic experiment described in these paragraphs? If the eye is offered bits and pieces of various types of paper that are smaller than the smallest formal elements characteristic of them, then the unaided eye no longer can recognize the particular type of paper. One then sees, so to speak, a paper that is not defined by its more detailed constitution. Even under favorable conditions of distance and illumination, my nearsighted vision can no longer distinguish between small pieces of assorted paper if they cover an area of only about .1 mm². To be sure, I recognize that all of the little pieces are paper, but no longer what type of paper. The impression of an indeterminate paper disappears when the little pieces are even smaller. Then the impression of “some material” replaces that specifying paper. These visual observations provided the impetus for studying the effect of reduction in size of the tactual surfaces. As already reported above, most 4-mm wide disks were still recognized as being paper; going to 2-mm wide tactual surfaces completely destroyed this impression. But this step did not also eliminate all of the distinctions in tactual impression that existed between the different papers. One can expect that if the size were further reduced, a limit would soon be reached at which the papers could no longer be distinguished from each other. Experimental proof could not be obtained for this, because it was not possible to punch or cut out smaller tactual surfaces without getting salient and misleading irregularities at the edge. The next variation of the basic experiment permits this goal to be reached in a different way. Before we report it, it seems best to introduce the concept of reduction of tactual impressions, which will be useful in developing the investigation.

Section 21. The Reduction of Tactual Impressions

In the World of Color (Katz, 1911, Sections 4 and 8), the concept of reduction of color impressions was introduced, whereby complete reduction was distinguished from partial reduction (which, to be sure, was not yet so designated there). At both levels of reduction, a relatively slight variation of the effective conditions of stimulation makes the impressions caused by the color stimuli more similar to each other. If partial reduction makes the perceived differences in the illumination of the surface colors recede or disappear, then complete reduction gives all colors the character of film color, even if they initially had a very different mode of appearance. Reduction reveals itself to be, on the one hand, a methodological principle, a causal-genetic question, such as that involved in ferreting out the structure of color perception, and, on the other hand, a classification scheme for the simplification and unification of the color impressions. Complete reduction funnels all color impressions into that of film color, which on more than one ground is held to be a color phenomenon of a particularly simple structure.

The concept of reduction procedures will now be introduced for the present area of investigation as well. We will indicate methods quite analogous to those in the case of color, by which a relatively slight variation of the effective conditions of tactual stimulation produces a relatively weak or strong simplification and unification of the tactual impressions. Given the dissimilarity in type of stimulation (and the absence as well of anything analogous to the ...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Contents
• Translator’s Preface
• Editor’s Introduction
• Author’s Preface
• Division I: Modes of Appearance of the World of Touch
• Division II: Quantitative Studies of the Tactual Performance
• Division III: Further Analysis of the Tactual Performance
• Division IV: Applications
• Author Index
• Subject Index