Visual Illusions: Their Causes, Characteristics and Applications — A Reader’s Guide

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Authors: Luckiesh, Matthew, 1883-1967 Digital Source: Project Gutenberg Gutenberg Release Year: 2011 First Publication Year: Not confirmed

Key Word: Optical illusions Target Reader: Readers of public-domain and historical texts

Book Edition: Project Gutenberg digital edition Book Language: en

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Words 59,471

Reading time 259 min

Text sections 10

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Source: Project Gutenberg record #36297

A 1922 study of static visual illusions, emphasizing experimental facts over theory. Luckiesh examines how physical measurements diverge from perception, using rotating disks, chromatic aberration, and color-sensation timing to demonstrate illusions' causes and practical applications.

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_THEIR CAUSES, CHARACTERISTICS AND APPLICATIONS_

DIRECTOR OF APPLIED SCIENCE, NELA RESEARCH LABORATORIES, NATIONAL LAMP WORKS OF GENERAL ELECTRIC CO.

AUTHOR OF "COLOR AND ITS APPLICATIONS," "LIGHT AND SHADE AND THEIR APPLICATIONS," "THE LIGHTING ART," "THE LANGUAGE OF COLOR," "ARTIFICIAL LIGHT--ITS INFLUENCE UPON CIVILIZATION," "LIGHTING THE HOME," ETC.

NEW YORK D. VAN NOSTRAND COMPANY EIGHT WARREN STREET 1922

Eventually one of the results of application to the analysis and measurement of the phenomena of light, color, lighting, and vision is a firmly entrenched conviction of the inadequacy of physical measurements as a means for representing what is perceived. Physical measurements have supplied much of the foundation of knowledge and it is not a reflection upon their great usefulness to state that often they differ from the results of intellectual appraisal through the visual sense. In other words, there are numberless so-called visual illusions which must be taken into account. All are of interest; many can be utilized; and some must be suppressed.

Scientific literature yields a great many valuable discussions from theoretical and experimental viewpoints but much of the material is controversial. The practical aspects of visual illusions have been quite generally passed by and, inasmuch as there does not appear to be a volume available which treats the subject in a condensed manner but with a broad scope, this small volume is contributed toward filling the gap.

The extreme complexity of the subject is recognized, but an attempt toward simplicity of treatment has been made by confining the discussion chiefly to static visual illusions, by suppressing minor details, and by subordinating theory. In other words, the intent has been to emphasize experimental facts. Even these are so numerous that only the merest glimpses of various aspects can be given in order to limit the text to a small volume. Some theoretical aspects of the subject are still extremely controversial, so they are introduced only occasionally and then chiefly for the purpose of illustrating the complexities and the trends of attempted explanations. Space does not even admit many qualifications which may be necessary in order to escape criticism entirely.

The visual illusions discussed are chiefly of the static type, although a few others have been introduced. Some of the latter border upon motion, others upon hallucinations, and still others produced by external optical media are illusions only by extension of the term. These exceptions are included for the purpose of providing glimpses into the borderlands.

It is hoped that this condensed discussion, which is ambitious only in scope, will be of interest to the general reader, to painters, decorators, and architects, to lighting experts, and to all interested in light, color, and vision. It is an essential supplement to certain previous works.

IV. Some types of geometrical illusions 44

V. Equivocal figures 64

VI. The influence of angles 76

VII. Illusions of depth and of distance 102

VIII. Irradiation and brightness-contrast 114

XII. Painting and decoration 179

XIII. Architecture 195

XIV. Mirror Magic 205

LIST OF ILLUSTRATIONS

1. Principal parts of the eye 14

2. Stereoscopic pictures for combining by converging or diverging the optical axes 41

3. Stereoscopic pictures 41

4. The vertical line appears longer than the equal horizontal line in each case 46

5. The vertical dimension is equal to the horizontal one, but the former appears greater 47

6. The divided or filled space on the left appears longer than the equal space on the right 49

7. The three lines are of equal length 50

8. The distance between the two circles on the left is equal to the distance between the outside edges of the two circles on the right 50

9. Three squares of equal dimensions which appear different in area and dimension 51

10. The vertical distance between the upper circle and the left-hand one of the group is equal to the overall length of the group of three circles 52

11. Two equal semi-circles 53

12. Arcs of the same circle 53

13. Three incomplete but equal squares 53

14. Middle sections of the two lines are equal 54

15. An effect of contrasting areas (Baldwin's figure) 54

16. An illusion of contrast 55

17. Equal circles which appear unequal due to contrast (Ebbinghaus' figure) 56

18. Equal circles appearing unequal owing to contrasting concentric circles 56

19. Circles influenced by position within an angle 57

20. Contrasting angles 57

21. Owing to perspective the right angles appear oblique and vice versa 58

22. Two equal diagonals which appear unequal 58

23. Apparent variations in the distance between two parallel lines 59

24. A striking illusion of perspective 60

25. Distortion of a square due to superposed lines 61

26. Distortion of a circle due to superposed lines 62

27. Illustrating fluctuation of attention 65

28. The grouping of the circles fluctuates 66

29. Crossed lines which may be interpreted in two ways 67

30. Reversible cubes 68

31. The reversible "open book" (after Mach) 69

32. A reversible tetrahedron 69

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Matthew Luckiesh opens Visual Illusions by declaring a "firmly entrenched conviction of the inadequacy of physical measurements as a means for representing what is perceived." This conviction drives the book's structure: rather than advancing a single theory, Luckiesh organizes his material around experimental demonstrations—rotating disks, colored patterns, and optical aberrations—that reveal how the eye and brain construct a world at odds with physical reality. The work is deliberately confined to static illusions, with occasional forays into motion and hallucination, and subordinates theory to observable facts. Luckiesh, a physicist at General Electric's Nela Research Laboratories, writes with an engineer's precision, but his subject repeatedly pulls him toward the subjective and the elusive.

The Primacy of Experimental Facts

Luckiesh explicitly subordinates theory to experiment, stating that he has "confined the discussion chiefly to static visual illusions, by suppressing minor details, and by subordinating theory." This is not a philosophical treatise but a catalog of demonstrations. The book's 100 illustrations—diagrams of disks, patterns, and optical setups—are its backbone. For instance, rotating a black-and-white Mason disk (Fig. 67) produces colored rings: reddish outermost, blue-green innermost, reversing with rotation direction. Luckiesh notes that the explanation "is not clear" due to unresolved debates in color-vision theory, but he presents the effect as a reproducible fact. This pattern recurs throughout: a phenomenon is described, its parameters given (speed, illumination, color), and then left largely unexplained. The reader is invited to replicate, not to speculate.

The Timing of Sensation: Growth and Decay

A recurring theme is the temporal dynamics of visual sensation. Luckiesh describes how sensations "grow and decay" at different rates depending on stimulus intensity and color. Blue-sensation "rises very rapidly and greatly overshoots its final steady value," with red and green following in that order. This is demonstrated by moving a red square on a blue-green background under low light: the red appears to "shake like jelly" and leaves a colored trail. Similarly, a luminous watch dial in a darkroom, when moved, shows green figures "separated from the red dial" and lagging behind. These effects are attributed partly to differences in the rates of growth and decay of color-sensations, though Luckiesh acknowledges that chromatic aberration may also play a role. The emphasis is on the measurable discrepancy between physical stimulus and perceptual response.

Chromatic Aberration and the Unstable Eye

Luckiesh devotes attention to the eye's optical imperfections, particularly chromatic aberration: the fact that the eye focuses different spectral colors at different points, like any simple lens. He describes how viewing a light source through a purple filter (transmitting only violet and red) produces a red or violet fringe depending on the eye's accommodation. This effect is "best witnessed on viewing a line spectrum" and underscores the theme that the visual system is not a neutral recorder but an active, flawed instrument. The discussion of chromatic aberration connects to earlier sections on color-sensation timing, suggesting that multiple physiological mechanisms—optical and neural—conspire to produce illusions. Luckiesh treats these not as errors to be corrected but as inherent features of human vision, with practical implications for design and lighting.

From Laboratory to Application

Though the book is grounded in laboratory demonstrations, Luckiesh repeatedly gestures toward practical applications. He notes that many illusions "can be utilized" and others "must be suppressed," particularly in fields like lighting, architecture, and display. The preface frames the work as filling a gap between theoretical studies and practical needs. For example, understanding the lag of color sensations can inform the design of moving signs or warning lights; awareness of chromatic aberration can improve optical instruments. Luckiesh's background at General Electric's Nela Research Laboratories—focused on applied science—shapes this orientation. The book does not provide explicit design rules, but it equips the reader with a repertoire of visual phenomena that could be exploited or avoided in real-world settings. The emphasis remains on experimental facts rather than prescriptive advice.

Luckiesh's Visual Illusions is best approached as a collection of carefully described experiments rather than a unified theory. Readers interested in the psychology of perception will find a wealth of reproducible phenomena, though the explanatory framework is deliberately thin. Those in applied fields—lighting, graphic design, optics—may discover useful demonstrations of how the visual system deviates from physical measurement. The book rewards slow reading, ideally with the opportunity to replicate the rotating-disk and color-motion experiments described. Its value lies not in final answers but in the precise documentation of perceptual puzzles that remain as provocative today as in 1922.

Reading Luckiesh’s careful measurements of what the eye insists on seeing, I felt a fond patience for our stubborn minds. We want straight lines where there are none, steadiness in spinning disks. It made me think of that old, strangely tender Cupid's Fair-Weather Booke Including an Almanack for Any Two Years (True Love Ought to Last That Long) — Reading Companion, where love, too, is a lovely miscalculation we happily keep.