BEHAVIORAL AND BRAIN SCIENCES (2003) 26, 375–444 Printed in the United States of America Gestalt isomorphism and the primacy of subjective conscious experience: A Gestalt Bubble model Steven Lehar Peli Lab, The Schepens Eye Research Institute, Boston MA 02114-2500. [email protected] http://cns-alumni.bu.edu/~slehar Abstract: A serious crisis is identified in theories of neurocomputation, marked by a persistent disparity between the phenomenologi- cal or experiential account of visual perception and the neurophysiological level of description of the visual system. In particular, con- ventional concepts of neural processing offer no explanation for the holistic global aspects of perception identified by Gestalt theory. The problem is paradigmatic and can be traced to contemporary concepts of the functional role of the neural cell, known as the Neuron Doc- trine. In the absence of an alternative neurophysiologically plausible model, I propose a perceptual modeling approach, to model the percept as experienced subjectively, rather than modeling the objective neurophysiological state of the visual system that supposedly sub- serves that experience. A Gestalt Bubble model is presented to demonstrate how the elusive Gestalt principles of emergence, reifica- tion, and invariance can be expressed in a quantitative model of the subjective experience of visual consciousness. That model in turn reveals a unique computational strategy underlying visual processing, which is unlike any algorithm devised by man, and certainly un- like the atomistic feed-forward model of neurocomputation offered by the Neuron Doctrine paradigm. The perceptual modeling ap- proach reveals the primary function of perception as that of generating a fully spatial virtual-reality replica of the external world in an in- ternal representation. The common objections to this “picture-in-the-head” concept of perceptual representation are shown to be ill founded. Keywords: brain-anchored; Cartesian theatre; consciousness; emergence; extrinsic constraints; filling-in; Gestalt; homunculus; indirect realism; intrinsic constraints; invariance; isomorphism; multistability; objective phenomenology; perceptual modeling; perspective; phe- nomenology; psychophysical parallelism; psychophysical postulate; qualia; reification; representationalism; structural coherence 1. Introduction know exactly how they address the issue of perceptual rep- resentation. But the most serious indictment of contempo- Contemporary neuroscience finds itself in a state of serious rary neurophysiological theories is that they offer no hint of crisis, for the deeper we probe into the workings of the an explanation for the subjective experience of visual con- brain, the farther we seem to get from the ultimate goal of sciousness. Visual experience is more than just an abstract providing a neurophysiological account of the mechanism recognition of the features present in the visual field – those of conscious experience. Nowhere is this impasse more ev- ident than in the study of visual perception, where the ap- parently clear and promising trail discovered by Hubel and Steven Lehar, Ph.D., is an independent researcher at Wiesel (1959) leading up the hierarchy of feature detection the Schepens Eye Research Institute in Boston, Mass., from primary to secondary and to higher cortical areas USA. He is the author of twelve different papers on sub- seems to have reached a theoretical dead end. Besides the jects ranging from new paradigms and forms of neuro- troublesome issues of the noisy stochastic nature of the computation, to philosophical papers on epistemology neural signal and the very broad tuning of the single cell as and the structure of conscious experience. A principle a feature detector, the notion of visual processing as a hier- focus of Lehar’s work is on the implications of Gestalt archy of feature detectors seems to suggest some kind of theory for the nature of perceptual computation and “grandmother cell” model in which the activation of a sin- representation in the brain, including the role of feed- gle cell or a group of cells represents the presence of a par- back in visual processing, and harmonic resonance as an ticular type of object in the visual field. However, it is not explanation for a number of illusory grouping phenom- ena. Lehar is also author of The World In Your Head: A at all clear how such a featural description of the visual Gestalt View of the Mechanism of Conscious Experience scene could even be usefully employed in practical interac- (2003; Erlbaum), a book that covers most of his theories tion with the world. across a wide range of subjects from vision to cognition Alternative paradigms of neural representation have to motor control. Lehar is winner of the 1999 Wolfgang been proposed, including the suggestion that synchronous Metzger award for significant contribution to Gestalt oscillations play a role in perceptual representation, al- theory, awarded by the Gestalt Theory and Applications though these theories are not yet specified sufficiently to (GTA) society. Downloaded© 2003 from https:/www.cambridge.org/coreCambridge University Press. Dartmouth 0140-525X/03 College, on $12.50 08 May 2017 at 15:51:22, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms375 . https://doi.org/10.1017/S0140525X03410091 Lehar: Gestalt isomorphism and the primacy of subjective conscious experience features are vividly experienced as solid three-dimensional first-person perspective as opposed to the external third- objects, bounded by colored surfaces, embedded in a spatial person perspective. The dual nature of a percept is analo- void. A number of enigmatic properties of this world of ex- gous to the representation of data in a digital computer, perience were identified decades ago by Gestalt theory, sug- where a pattern of voltages present in a particular memory gestive of a holistic emergent computational strategy whose register can represent some meaningful information, such operational principles remain a mystery. as a numerical value, a brightness value in an image, or a The problem in modern neuroscience is a paradigmatic character of text, when viewed from inside the appropriate one that can be traced to its central concept of neural pro- software environment, but when viewed in external physical cessing. According to the Neuron Doctrine, neurons behave terms those same data take the form of voltages or currents as quasi-independent processors separated by relatively in particular parts of the machine. However, whatever form slow chemical synapses, with strictly segregated input and is selected for encoding data in the computer, the informa- output functions through the dendrites and axon, respec- tion content of that data cannot possibly be of higher di- tively. It is hard to imagine how such an assembly of inde- mensionality than the information explicitly expressed in the pendent processors could account for the holistic emergent physical state of the machine. properties of perception identified by Gestalt theory. In The same principle must also hold in perceptual experi- fact, the reason these Gestalt aspects of perception have ence, as proposed by Müller (1896) in the psychophysical been largely ignored in recent decades is exactly because postulate. Müller argued that because the subjective expe- they are so difficult to express in terms of the Neuron Doc- rience of perception is encoded in some neurophysiologi- trine paradigm. More recent proposals that implicate syn- cal state, the information encoded in that conscious experi- chronous oscillations as the neurophysiological basis of con- ence cannot possibly be any greater than the information scious experience (Crick 1994; Crick & Koch 1990; Eckhorn encoded in the corresponding neurophysiological state. Al- et al. 1988; Llinas et al. 1994; Singer 1999; Singer & Gray though we cannot observe phenomenologically the physi- 1995) seem to suggest some kind of holistic global process cal medium by which perceptual information is encoded in that appears to be more consistent with Gestalt principles, the brain, we can observe the information encoded in that although it is hard to see how this paradigm, at least as cur- medium, expressed in terms of the variables of subjective rently conceived, can account for the solid three-dimen- experience. It follows therefore that it should be possible sional nature of subjective experience. The persistent dis- by direct phenomenological observation to determine the parity between the neurophysiological and phenomenal dimensions of conscious experience, and thereby to infer levels of description suggests that either the subjective ex- the dimensions of the information encoded neurophysio- perience of visual consciousness is somehow illusory, or the logically in the brain. state of our understanding of neural representation is far The bottom-up approach that works upward from the more embryonic than is generally recognized. properties of the individual neuron and the top-down ap- Pessoa et al. (1998) made the case for denying the pri- proach that works downward from the subjective experi- macy of conscious experience. They argued that although ence of perception are equally valid and complementary the subjective experience of filling-in phenomena is some- approaches to the investigation of the visual mechanism. times accompanied by a neurophysiological correlate, such Eventually, these opposite approaches to the problem must an isomorphism between