The Munker Illusion: Science and Philosophy by Jack Schwartz
The Munker Illusion is offered as yet another example of a so-called optical ‘illusion’. Illusions have historically been offered as proof that we cannot trust our senses and that all ideas that depend upon sense-perception are therefore unreliable, leading to absolute skepticism, solipsism, and subjectivism, ideas that dominate modern philosophy.
The interpretation of the Munker effect as an instance of perceptual illusion, is the consequence of failing to grasp the true nature of perception, the nature of what our senses are ‘designed’ to detect and process, and attempting instead to rewrite the laws of perception to meet the philosophical demands for ‘valid’ contact with the ‘real world’, typically implying unmediated or unprocessed interaction with the real properties of the physical world. A typical example of such a demand is the assertion that if our senses were valid they would allow us to sense the real colors, temperatures, density, geometry, odors, sounds of objects ‘in themselves’ and not be limited to the subjective experiences that are the result of processing and filtering the ‘information’ sent to our senses by external objects.
Property Identity Fallacy versus the Proper Nature and Function of Perception:
This demand (a species of the psycho-physical property identity fallacy) is totally misguided, both biologically, and epistemologically. The facts are these: (1) The purpose of the senses is not to apprehend absolute physical properties of external reality, but to provide us with a set of processes for identifying only those properties of the external world, and our relationship to it, that allow us to effectively engage the world in order to explore it and live in it. (2) How this is accomplished involves a complex process depending on the simultaneous interactions between energy gradients, propagation mediums (air and water for example), sensory organs that register, process and filter the dynamic structure of simultaneous contrasting energy gradients across energy patterns and boundaries. (3) Necessary for this processing is an active conscious organism that is able to simultaneously engage with and respond to the object-specifying patterns in the energy flux registered by the organism’s sensory system, such interaction constitutes the necessary condition of sensory/perceptual ‘exploration and discovery of the environment.’ (4) As a consequence of the sensory/perceptual processing, what we perceive are not the simple energy mapped properties of the external world (i.e., their absolute energy values corresponding to physical wavelength, thermal intensity, acoustical frequencies, or baric pressure). Instead, our perceptual systems identify complex information features such as dynamic invariants within simultaneous contrasting energy values across sharp energy gradient ‘cliffs’. If this sounds like J. J. Gibson, it is because my views are deeply informed by that great perception scientist and by his brilliant wife and scientific collaborator E. J. Gibson. (See more about their work below. Also see my master’s thesis entitled The Causal Basis of Perception, based on Gibson’s theories of perception.)
To what do Perceptions Correspond?
As a consequence, the psychological experiences of such conscious events as ‘color’, ‘sound’, ‘touch’ correspond to complex relational physical constancies (contrasting rations of long to short wavelengths across a visual edge), rather than simple physical local constancies (wavelength, for example). Thus the perception of ‘red’ corresponds not to the detection of light waves in the 620–750 nm range (as many physicists and philosophers would have it), but rather the contrasting ratios of wavelength (or frequencies) across a physical ‘edge’ or ‘optical boundary’. That perception of ‘red’ is always reliable and always tells us exactly what long-short contrasting rations exist at that moment in that given optical direction in the real world. Thus, surprisingly, perception tells us far more than we expect it to tells us. It identifies a physically complex fact and not a physically simple one.
The Causal Basis of Perception as a Scientific Question:
While a valid philosophy can tell us that our perceptual awareness of the world is reliable and the necessary basis for conceptual ideation, it is the job of science, not of philosophy to study and understand the underlying causal nature of perception as a psycho-physical-biological developmental capability of the conscious organism. In other words, it is the job of science to discover how our perception of ourselves and the external world, specifically ourselves in relation to the external world, is achieved.
Gibson as the Key to Understanding the Causal Basis of Perception:
There is much science to learn before understanding how the senses give us true reliable perceptual knowledge of the external world. A good place to begin is by reading the works of J. J. Gibson, especially his brilliant and challenging thesis: The Senses Considered as Perceptual Systems as well as his magnum opus, The Ecological Approach to Visual Perception. J. J. Gibson is an advocate of epistemological realism (as contrasted with the many flavors of idealism on the one hand and materialist reductionism on the other).
In his 1967 paper New Reasons for Realism, Gibson wrote:
If invariants of the energy flux at the receptors of an organism
exist, and if these invariants correspond to the permanent properties
of the environment, and if they are the basis of the organism’s
perception of the environment instead of the sensory data on which we
have thought it based, then I think there is new support for realism
in epistemology as well as for a new theory of perception in
psychology. – Gibson - New Reasons for Realism, Synthese, 17:2
(1967:juni) p. 162.
In the Summary of this paper, Gibson wrote:
Both the psychology of perception and the philosophy of perception
seem to show a new face when the process is considered at its own
level, distinct from that of sensation. Unfamiliar conceptions in
physics, anatomy, physiology, psychology and phenomenology are
required to clarify the separation and make it plausible. But there
have been so many dead ends in the effort to solve the theoretical
problems of perception that radical proposals may now be acceptable. –
op. cit., p. 171.
J. J. Gibson began working on the problems of visual perception with his future wife and collaborator Eleanore J. Gibson whose major extensions of J. J. Gibson’s work was her deep research into perceptual learning. E. J. Gibson extended J. J.’s work reflected in his The Senses Considered. Her first important book was Principles of Perceptual Learning and Development. Later her collaboration with J.J. on ecological visual perception inspired her magnum opus An Ecological Approach to Perceptual Learning and Development.
Sensory ‘Illusions’ as a Species of Functional Isolation and the Argument from Pathology
Returning to the issue of sensory illusions, the most important concept to realize is that no theory of perception can be built on theories of perceptual or sensory illusions. Why? For the very same reasons that no theory of biology or physiology can logically be built on the basis of biological functional pathology. Pathological systems are by their very nature malfunctioning systems. Pathology is explained as corruptions of healthy or properly integrated and functioning physical, biological or psychological systems. Illusions are the consequences of the carefully contrived ‘unnatural’, ‘deficient’, ‘constrained’ or ‘restrictive’ presentation of isolated visual (tactile, auditory, etc) sensory ‘stimuli’. It is the very fact that these presentation techniques prevent adequate exercise of the subject’s full perceptual capacities that leads to the ambiguity and vagueness that characterize so-called sensory illusions. When inadequate sensory information is presented to the subject, it should not be surprising that the resulting experience is to that very extent non-veridical and always associated with the feeling of ambiguity and uncertainty.
Similarly in the realm of neurophysiology, experimenters typically isolate some part of the nervous system (often using severe isolation) so that only the most primitive sensory-motor phenomenon can occur and be accurately observed and measured. It is a methodological illusion to believe that the results of such anatomical/physiological isolation, such as the extensive experimental work on ‘the reflex arc’, represent the primitive bases for and are revelatory of the neuromuscular principles underlying normal integrated behavior. This approach fails to recognize and appreciate the implications of The Integrative Action of the Nervous System (Sir Charles Sherrington, 1906) .
Similar errors occur in the study of embryological development, where local isolated phenomenon are mistakenly taken for fundamental biochemical elements of biogenesis. See the work of Paul A. Weiss, an innovator and mentor in the field of neurophysiology. Weiss once wrote: “Of what do we deprive a system when we dismember it and isolate its component parts, whether bodily or just in our minds? Plainly, of the interrelations that had existed among the parts while they were still united.” – from Paul Weiss, “One Plus One Not Equal Two” in The Neurosciences: A Study Program, pp. 801-821.
This fallacy of construction by structural or functional decomposition permeates much of science, particularly biological science leading to may false doctrines and theories. Underlying this general methodology is the dogma of mechanistic reductionism and functional or elemental reductionism, which holds that a system can be fully understood as the additive product of the actions of its individual parts.
Isolating sensory receptors thus preventing sensory exploration and proper sensory function can only lead to sensory-motor inadequacy and the common phenomenon of sensory ‘illusions’. We conclude that this method of sensory isolation commits the same methodological errors cited above, leading to fallacious conclusions regarding the functioning of our sensory-motor systems.