Hermann von Helmholtz (1821–1894)
Hermann von Helmholtz was a German physicist trained in medicine, who later made significant contributions in physiology and psychology that involved the many connections between mathematics and vision, science and perception, through his studies of spatial cognition, color vision, tone sensation, and sound perception. He coined this area of his studies ‘psychophysics,’ or the relations between physical, concrete phenomena and human perception.
Around the time that Helmholtz developed the opthalmoscope (1851), the invention that he is perhaps most well known for, he published a text A Treatise of Physiological Optics which addressed depth- and motion- perception and color vision. In his 1867 third volume of this text, his interest in the perceptual implications of optics demonstrated a clear belief in the physiology of vision beyond its purely medical and scientific applications. Helmholtz refers to unconscious inference, the reactive and instinctive human mechanism that impresses visual stimuli, as a prominent and important part of building perception. In this way, Helmholtz’ practice as an inventive scientist, creating instruments that are now — in improved forms — routinely used as part of eye examinations, went hand in hand with his elaborations on vision and perception.
Within the realm of sound and perception, Helmholtz examined similar principles of reactive human impulses and tendencies of subconscious and random sense-making through his invention of the Helmholtz resonator. It is said to have measured and created frequencies of complex multiple tones that when played together, had similarities to the sounds of words or vowels. He expanded on his invention in his text On the Sensations of Time, emphasizing the aesthetic dimensions of acoustics and sound, and regarding the senses as interconnected and able to influence one another.
From these ideas of the interrelations between the measurable and the perceptual has developed what is known as the Helmholtz principle, through which it is stated that while a uniformly random image does not create a perception of structure, “whenever some large deviation from randomness occurs, a structure is perceived … we immediately perceive whatever could not happen by chance” (Desolneux, Moisan, Morel, 31). Many exercises within the study of the Helmholtz principle involve an assessment of ‘events’ that are meaningful against those that are coincidental. Through an examination of the science and mechanisms of vision and audition, Helmholtz strove to parse out the significances of involuntary movement responses to certain physical stimuli.
For example, Fig. 3.3 above illustrates the relativity in perception of the angled lines as being random (on left) or among a set of determined angles (on right). In other words, on the left we perceive lines that have been scattered by chance — the scattered perception remains in the image on the right, but we “immediately perceive the alighnment as a large deviation from randomness that could hardly happen by chance” (Desolneux, Moisan, Morel, 38).
Similarly, Figure 3.4 describes the emergence and identification of a meaningful event on left and middle charts, and the disappearance of such perception of coincidence despite it being still present, on the right. We are able to identify in the left two charts a deviation from randomness, while in the right chart “the alignment is no more meaningful (and no longer visible)” (Desolneux, Moisan, Morel, 41).
On Goethe, who had written on color vision at the time Helmholtz was also examining this topic, Helmholtz once wrote that he was “a poet and as such would always view phenomena subjective, immediately. The scientist, on the other hand, seeks to discover the strings, pulleys, and wheels which operate behind the scenery” (Westheimer, 6). Through his studies and justifications in science, Helmholtz transcended the analogical, practicing rigorously in the interaction between his medical and scientific backrounds and his perceptual, visual theories — one always measured by the other, and “find[ing] the basis of one in the other” (Westheimer, 7).
Desolneux, Agnes, Moisan, Lionel, and Morel, Jean-Michel. “Edge detection by Helmholtz Principle.” Journal of Mathematical Imaging and Vision. Kluwer Academic Publishers. 2001.
Desolneux, Agnes, Moisan, Lionel, and Morel, Jean-Michel. “The Helmholtz Principle.” From Gestalt Theory to Analysis: A Probabilistic Approach. Springer. 2008.
Helmholtz, Hermann. On the Sensations of Tone as a Physiological Bases for the Theory of Music. Cambridge University Press. 2009.
Helmholtz, Hermann. Southall, James P.C. ed. Treatise on Physicological Optics. Volume III. General Publishing Company, Ltd. Toronto.
Keeler, Richard C. “The Opthalmoscope in the Lifetime of Hermann von Helmholtz.” Arch Opthalmol. 2002.
Westheimer, Gerald. “Hermann Helmholtz and origins of sensory physiology.” Trends in Neurosciences. Volume 6. Elsevier Biomedical Press, 1983. pp 5–9.