Tag Archives: perception

Is Visual Perception Really a Nonstop Hallucination? A Plea for Conceptual Revision

Anyone who has taken Philosophy of Mind 101 will be familiar with the following claim: “We’re hallucinating reality all the time”. In this post, I will critically examine whether this statement should be taken as literally true. My intuition is that such claims are over-extended metaphors, and the true nature of visual perception is more complicated.

The popularity of the Matrix has provided a common conceptual framework to make sense of what philosophers and vision scientists have been claiming for many years e.g. Helmholtz’s claim that perception is a “unconscious inference”. The original philosophical motivation can be traced to Descartes’ musings about whether we could ever distinguish reality from a dream. Nowadays, vision scientists frame these ideas in terms of vision being “representational”.

But is it true? The argument is prima facie convincing. Start with the phenomenon of visual illusions or visual hallucinations. For example, in Charles Bonnet Syndrome (CBS) people have “complex” visual hallucinations wherein people and objects are hallucinated wholesale in dazzling detail. These fascinating cases clearly  demonstrate the brain is able to “represent” or “generate” non-existent objects in full phenomenological detail. But here’s the crucial move: if the brain can generate complex visual hallucinations, is it possible that ALL perception is a complex visual hallucination?

But as with all questions of possibility, we should be skeptical of any argument that jumps from possibility to actuality. Sure, it seems possible that ALL perception is a hallucination, but are we forced to make this conclusion on the basis of knowing that complex visual hallucinations are possible? Not at all!

I’d like to suggest a different metaphor for understanding the relation between hallucinations and normal perception that preserves their essential difference rather than collapsing them into a single, continuous category. Instead of thinking the existence of hallucinations forces us to think we are in the Matrix, I think it’s more useful to think of hallucinations as akin to augmented reality.

augmented

The idea is fairly straightforward: hallucinations such as CBS are analogous to the augmented “over-lay” in the above picture. The basic idea is that there is a more-or-less continuous stream of “veridical” perception underlying our basic animal perception and that complex hallucinations such as CBS are “projected upon” that stream just as an augmented reality HUB projects upon normal perception.

I think the AR metaphor for perception is more plausible than the wholesale Matrix hypothesis. My reasoning is grounded by an evolutionary thought experiment. Suppose for the sake of argument that the Matrix metaphor is correct and that ALL perception is a hallucination. Presumably, the brain is responsible for generating these representations. A further assumption is that more-or-less all mammalian brains have a similar hallucination generation capacity. But how did such a capacity evolve over time? Take the earliest mammalian ancestor who lived “fully” in the Matrix of their brain. How did their parent’s brain work? Was their perception only 99% a hallucination? And their ancestors’ perception 98% hallucinatory? And so on.

As we imagine the slow evolution of Matrix-style perception, we are faced with a Sorites paradox of sorts. As nervous systems get simpler and simpler it becomes implausible that nervous systems composed of only several hundred neurons are generating a completely hallucinatory inner-model. The neurons are more likely acting as a kind of complex “mediation” between stimulus and response rather than a representational medium.

But if we start going forward in evolutionary time and nervous systems get more and more complicated, it seems wrong to me to think that the brain ever “gets rid of” that underlying non-representational form of perception. Rather, the brain “adds” onto that basic veridical perception. But at no point will the nervous system switch from 50/50 veridical-hallucinatory to 100% hallucinatory such that we become fully immersed in the Matrix. Like augmented reality, the most evolutionary recent brain developments like the neocortex “overlay” more basic forms of perception.We might think of hallucinations like CBS as neocortical memory-patterns that are projected upon the real-time dynamic stream of veridical perception.

Obviously this post represents a very rough-and-ready formulation of an alternative to the standard Matrix metaphor and will need much further development. But on the other hand, I am skeptical that the Matrix metaphor has ever been rigorously developed past the level of intuitive metaphor. It’s even possible that we can never move beyond metaphor in dealing with the most unknown and esoteric psychological phenomena. And if this is the case, we have a real imperative to reexamine popular metaphors such as the Matrix and replace them with new ones.

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A crude theory of perception: thoughts on affordances, information, and the explanatory role of representations

Perception is the reaction to meaningful information, inside or outside the body. The most basic information is information specific to affordances. An affordance is a part of reality which, in virtue of its objective structure, offers itself as affording the possibility of some reaction (usually fitness-enhancing, but not necessarily so). A reaction can be understood at multiple levels of complexity and mechanism. Sucrose, in virtue of its objective structure, affords the possibility of maintaining metabolic equilibrium to a bacteria cell. Water, in virtue of its objective structure, affords the possibility of stable ground for the water strider. Water, in virtue of its objective structure, does not afford the possibility of a stable ground for a human being unless it is frozen. An affordance then is, as J.J. Gibson said, both subjective and objective at the same time. Objective, because what something affords is directly related to its objective structure; subjective, because what something affords depends on how the organism reacts to it (e.g. human vs. water strider)

The objective structure of a proximal stimulus can only be considered informationally meaningful if that stimulus is structured so as to be specific to an affordance property. If a human is walking on the beach towards the ocean, the ocean will have the affordance property it has regardless of whether the human is there to perceive information specific to it. The “success” or meaningfulness of the human’s perception of the ocean is determined by whether the proximal stimulus contains information specific to that affordance property. A possible affordance property might be “getting you wet”, which is usually not useful, but can be extremely useful if you are suddenly caught on fire. Under normal viewing conditions, the objective structure of the ambient array of light in front of the human contains information specific to the ocean’s affordance properties in virtue of its reflective spectra off the water and through the airspace. But if the beach was shrouded in a very thick fog, the ambient optic array would stimulate the human’s senses, but the stimulus wouldn’t be meaningful because it only conveys useless information about the ocean, even though that information is potentially there for the taking if the fog was cleared. An extreme version of “meaningless stimulus without perception” is the Ganzfeld effect. On these grounds, we can recreate, without appealing to any kind of representational theory, the famous distinction between primary and secondary qualities i.e. the distinction between mere sensory transduction of meaningless stimuli and meaningful perception.

Note too how perception is most basically “looking ahead” to the future since the affordance property specifies the possibility of a future reaction. This can be seen in how higher animals can “scan” the environment for information specific to affordances, but restrain themselves from acting on that information until the moment is right. This requires inhibition of basic action schemas either learned or hardwired genetically as instinctual. In humans, the “range” of futural cognition is uniquely enhanced by our technology of symbols and linguistic metaphor. For instance, a human can look at a flat sheet of colored paper stuck to a refrigerator and meaningfully think about a wedding to attend one year in the future. A scientist can start a project and think about consequences ten years down the road. Humans can use metaphors like “down the road” because we have advanced spatial analogs which allow us to consciously link disparate bits of neural information specific to sensorimotor pathways into a more cohesive, narratological whole so as to assert “top-down” control by a globally distributed executive function sensitive to social-cultural information.

This is the function which enables humans to effortlessly “time travel” by inserting distant events into the present thought stream or simulating future scenarios through conscious imagination. We can study the book in our heads of what we have done and what we will do, rehearse speech acts for a future occasion, think in our heads what we should have said to that one person, and use external symbolic graphs to radically extend our cognitive powers. Reading and writing, for example, has utterly changed the cognitive powers of humans. Math, scientific methodology, and computer theory have also catapulted humans into the next level of technological sophistication. In the last few decades, we have seen how the rise of the personal computer, internet, and cellphone has radically changed how humans cope in this world. We are as Andy Clark said, natural born cyborgs. Born into a social-linguistic milieu rich in tradition and preinstalled with wonderful learning mechanisms that soak up useful information like sponges, newborn humans effortlessly adapt to the affordances of the most simple environmental elements (like the ground) to the most advanced (the affordance of a book, or a website).

So although representations are not necessary at the basic level of behavioral reaction shared by the unicellulars (bacteria reacting to sucrose by devouring it and using it metabolically), the addition of the central nervous system allows for the storage of affordance information into representational maps. A representational map is a distributed pattern of brain activity which allows for the storage of informational patterns which can be utilized independently of the stimulus event which first brought you into contact with that information. For example, when a bird is looking right at a food cache, it does not need its representational memory to be able to get at the food; it simply looks at the cache and then reacts by means of a motor program for getting at the food sparked by a recognition sequence. However, when the cache is not in sight and the bird is hungry, how does the bird get itself to the location of the cache? By means of a re-presentation of the cache’s spatial location which was originally stored in the brain’s memory upon first caching the food. By accessing stored memory-based information about a place even when not actually at that place, the bird is utilizing representations to boost the cognitive prowess of its nonrepresentational affordance-reaction programs. Representations are thus a form of brain-based cognitive enhancement which allow for the reaction to information which is stored within the brain itself, rather than just contained in the external proximal stimulus data. By developing the capacity to react to information stored within itself, the brain gains the capacity to organize reactions into more complicated sequence of steps, delaying and modifying reactions and allowing for the storage of information for later retrieval and the capacity to better predict events farther into the future (like the bird predicting food will be at its cache even though it is miles away).

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Tyler Burge begs the question against nonrepresentationalism

There is an interesting article by Tyler Burge in the NY Times philosophy blog called “A Real Science of Mind” that I happen to disgree with vehemently. He basically claims that representationalism is the only game in town when it comes to explaining visual perception. In fact, he doesn’t even hint at the fact that representationalism is but one theory, and one supported by philosophically ambiguous explanations of what it means to actually “represent” something. Indeed, he says:

Explanation in perceptual psychology is a sub-type of task-focused explanation.  What makes it distinctively psychological is that it uses notions like representational accuracy, a specific type of correlation…Why are explanations in terms of representational accuracy needed?  They explain perceptual constanciesVisual perception is getting the environment right — seeing it, representing it accurately…Perceptual psychology explains how perceptual states that represent environmental properties are formed.

Now, it seems to me that Burge has massively begged the question against nonrepresentational explanations of low-level visual perception.

In  making this claim, I put myself in a precarious position. One of the main points of Burge’s article is that vision science is a highly developed and “mathematically rigorous” science. Burge is insistent that vision science is on solid explanatory ground and I have no intention of challenging the mountain of empirical evidence gathered by orthodox representational visual science. No, the question is not about the facts, but rather, about the interpretation of the facts. It is my claim that representationalism is but one way of interpreting the empirical facts gathered by orthodox visual science.

My claim goes as follows: talk about the visual creature “accurately representing” the environment can be replaced, without losing any explanatory power, by talk of “discriminating information” in the environment. Some would say this is merely a matter of semantics, and in a way they would be right. But when it comes to philosophical explanations of visual perception, semantics are of the utmost importance. But why bother with this semantic triviality between “representation” and “discrimination”? Aren’t they the same thing? In a way, yes. But, as William Ramsey has argued in his important book Representation Reconsidered, this theoretical equivalency is actually the result of orthodox visual science moving away from classic forms of representationalism. For when a visual scientist claims that the organism “accurately” represents a feature of the environment in perception, all the explanatory work is being done by the neural workhorse that is the brain. And, naturally, this explanation is ultimately cashed out in physiological terms, against Burge’s claim that visual science is truly representational.

It is my contention that talk of “differentiation” or “discrimination” is just as psychological as talk of “representation”, but discrimination is more ontologically coherent. Take the example of a hungry primate perceiving a juicy red strawberry. Orthodox visual science would say that in successfully perceiving the strawberry the primate must have accurately represented the red strawberry as a red strawberry, (and not, say, as a purple poisonberry). This is the classic representationalist explanation. On my view, it would be more philosophically parsimonious to say that in successfully perceiving the strawberry, the primate discriminated the strawberry from out of the ambient array of energy surrounding the strawberry. Another way of putting it would be that in perceiving the red strawberry the primate attended to the information specific to the features of the strawberry that were relevant to its internal needs, namely, hunger.

On this account, the primate can be said to perceive the red strawberry as nutritious, not as a strawberry. Notice how this is starkly different from the representationalist interpretation. For the representationalist, the primate’s perception of the strawberry is cashed out in terms of how accurately the internal representation is in comparison to the objective features of the strawberry. If the primate represents the strawberry as being red, and the strawberry really is red, then the primate’s perception of the strawberry is said to be “accurate”, and thus successful. It is then said that the brain consults the representation when forming its intentions to act. Orthodox visual theory is thus committed to what some philosophers have called the sense-represent-planact model. The primate receives proximal sense-data, tries to form an accurate representation of distal stimulus, consults the representation to form a plan, and then executes a motor command to pluck the strawberry and bring it into its mouth.

On my interpretation, we can eliminate the “represent” and “plan” stages and replace it with a sensorimotor model. On this account, the task of the brain is to discriminate the meaningful information already in the environment by attending to it. Neurally speaking, the discrimination supervenes upon the neural patterns of activity. So how is this different from the representationalist story? Because unlike Burge, I think the behavioral nature of discriminatory perception is actually a plus, not a downside (and of course, behavioral explanations are a kind of psychological explanation unless we beg the question against behaviorism). So we shouldn’t expect visual neuroscience to engage in representational theorization when the proper explanatory level of description is behavioral, not representational. I have never seen a representational theory that avoided the homunculus problem without merely collapsing into descriptions of the behavior of  neurons.

And for good reason. Although Burge claims that representation is well understood by visual science, he is only half-right. Representation is well understood if by that we mean that we understand the neural underpinning and physiological correlations of the representation. But as William Ramsey has argued, this is precisely the point. Orthodox visual science has never actually successfully explained how a representation actually functions as a representation, as opposed to being a merely physiological mediator in a long chain of neural activity that ultimately leads to effective motor behavior.

So while Burge is perfectly right to say that “neuralbabble” is nonexplanatory on the psychological level, I believe he is mistaken when he claims that representationalism offers a philosophically rigorous interpretative framework that explains the phenomena at hand. Burge recognizes this when he talks about “generic representations” that apply so widely to any causal correlation as to no longer being explanatorily useful in cognitive science. To make representation explanatorily worthwhile, he introduces the notion of “accuracy”. But as I attempted to explain above, there is an alternative interpretation of accuracy available that focuses on the accurate perception of an affordance. But, crucially, the accurate perception of an affordance is entirely different than the accurate representation of an objective feature. This is because the affordance is more directly tied into the motivational circuits and can thus undercut the “represent” and “plan” stages of the sense-represent-plan-act model and jump right into the scientifically respectable arena of “sensation” and “action”. Hence, sensorimotor models of visual perception. The notion of accurately representing objective features of the environment is replaced by the accurate discrimination of information specific to invariant properties of objects which are themselves specific to affordances (opportunities for behavior). Perceiving the strawberry then becomes a matter of attending to those features of the strawberry which either past experience or innate knowledge has taught to be relevant to homeostatic needs.

Hence, we can account for the normative or “psychological” component of perception (its possible success or failure) in terms of how well the organism is capable of detecting information specific to properties that are themselves specific to affordances. And this offers us a path towards a “real science of mind”. Why? Because affordance perception is directly tied into those sensorimotor causal pathways that have been so successfully studied by orthodox visual science. And it does this without invoking a notion of one thing somehow “standing in for” something else.

Now, my representational critics will respond by saying that the discrimination of information specific to affordances is no more understood than is the notion of accurately representing the environment. Point well taken. But it is my contention that orthodox visual science has been talking about discrimination all along. So I really don’t see myself as being a “revolutionary”. I contend that we could go into almost every single visual science article and change “represents” with “discriminates” without losing any explanatory value. In fact, I think this semantical change would actually enhance the explanatory power of visual science precisely because “discrimination” is more ontologically tractable insofar as it doesn’t make a sharp distinction between the “merely mechanical” sensation of a bacterium and the “cognitive” perceptual capacities of “representing creatures”. One could say that my theory offers a “flat ontology” wherein all lifeforms are said to share in the capacity for discrimination of information and reactivity in direct response to that discrimination. Accordingly, my interpretation is immediately amenable with the advances being made in evolutionary biology.

Moreover, and most importantly for my purposes, the rejection of representationalism for an explanation of basic visual perception would leave room for those phenomena that truly deserve a representational explanation: human symbolic cognition. Indeed, in rejecting representationalism for the explanation of basic visual perception I do not reject all representational explanations like Anthony Chemero does. I thus think, following Clark and Toribio, that some phenomena are “representation hungry”, while others aren’t. Following Gibson, I do not think that basic visual perception as shared by most animals on this planet is representation hungry. What I do think absolutely requires a representational explanation is the symbolic and linguistic cognition of humans. For the referential system that is language absolutely requires an explanation of how one thing (a linguistic symbol) could “stand in for” something else. For example, the word “strawberry” cognitively stands in for a real strawberry. Now, I’m not claiming to have a complete theory worked out about symbolic cognition. But I think significant progress in the mind sciences would be made if we all recognized this demarcation between the nonrepresentational, sensorimotor cognition we share with nonhuman animals and the representational, symbolic cognition seemingly unique to humans.

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Neuroscientists are Kantian Anti-Realists

From Michael Rohlf’s new SEP article on Immanuel Kant:

[According to Kant], the sensible world, or the world of appearances, is constructed by the human mind from a combination of sensory matter that we receive passively and a priori forms that are supplied by our cognitive faculties. We can have a priori knowledge only about aspects of the sensible world that reflect the a priori forms supplied by our cognitive faculties.

[T]he Critique claims that pure understanding too, rather than giving us insight into an intelligible world, is limited to providing forms — which he calls pure or a priori concepts — that structure our cognition of the sensible world. So now both sensibility and understanding work together to construct cognition of the sensible world, which therefore conforms to the a priori forms that are supplied by our cognitive faculties: the a priori intuitions of sensibility and the a priori concepts of the understanding.

Here we can see the intellectual foundations for modern neuroscience’s claim that the objects we experience are illusionary constructions generated from the brain making hypotheses and guesses about how the world is based on ambiguous sensory input. The key idea here is construction. An internal mental construction implies a disconnection from the objects themselves. When grasping a coffee mug, my vision is not directed towards the cup itself, but rather, towards an internal construction the brain generates. According to Kantian neuroscience, the mug I experience is not real; it is a simulation. Neuroscience is thus an intellectual descendant of Kantian anti-realism. Indeed, 20th century positivism collapsed into representational phenomenalism despite its claim to be “anti-metaphysical” and modern neuroscience has subsequently followed suit with little critical discussion.

For neuroscience as for Kant, experience is a construction. This means that the mind is directed towards representations. Of course, Kantian neuroscientists claim that the physically sensitive brain actually bumps up against the real world through its corporeal body. It’s just that low-level physical bumping is not sufficient for conscious experience; the brain must take the bumpings and then operate on them in order to generate or construct a “percept”, which is experienced by the mind. The mind is always directed towards these percepts rather than objects themselves. The coffee mug in my hand is nothing but an internally generated percept, which may or may not “correspond” with the real. This of course inevitably opens up the possibility of brain-in-a-vat external world skepticism and radically skeptical epistemological worries such as the “problem” of illusion and hallucination. Moreover, internalists like Thomas Metzinger avoid the inevitable homuncular problem by supposing that the construction views itself or, put another way, the screen upon which the construction is projected is the whole system. In other words, Metzinger claims that one can have a theater without an audience.

I take this to be wildly unparsimonious. Surely the operation of constructing an incredibly complex phenomenal percept is costly. If thinkers like Metzinger are willing to throw away the self in their theories, why not throw away the projective-theater metaphor which was originally developed to accommodate a robust theory of selfhood? If our metaphysics bottoms out in brain activity, behaviorism is the more parsimonious theory. But this would be a hybrid behaviorism that incorporates “internal phenomena” such as mind-wandering, introspection, episodic memory, internal speech, working memory (visual sketchpad, phonological loop, reconstructive imagination), etc. In the same way that Metzinger argues for a selfless theory of percept construction, I would argue for a selfless theory of mind-wandering and introspection.

Selfless is perhaps a misnomer because under my theory, the self is very much real insofar as it is the transcendental entity which “performs” the operations of introspection. However, this self (call it an “analog self”), can itself be seen as a virtual construction which is operationalized whenever internal phenomena arise. The imaginings of the mind-eye couldn’t operate unless there was a virtual perceiver but this perceiver is “self-organizing” in the way that Metzinger’s self-viewing theater is. The key difference between myself and Metzinger however is that I claim the selfless selving of introspection is operative only periodically whereas Metzinger claims that selving is operative for all experience, including ordinary perception of the real. For me, experience is divided between conscious, self-reflexive introspection and behaviorist automatisms constituted by instinct, reflex, habit, and learned, automated skills. These automatisms ground introspection both ontogenetically and phylogenetically. Phylogenetically, because automatic, nonvoluntary behavior preceded conscious, deliberate mental acts by millions of years. Ontologically, because nonconscious behavioral reactivity characterizes the experience of human infants; introspection is a skill we learn through exposure to the appropriate cultural scaffolds (language, folk psychological discourse, etc.). Selving is thus something that, as Heidegger says, exists primarily as a counter-possibility to automatic behavior. The self is not foundational for experience, but rather, is a mode of experience derivative from our more primordial absorption into familiar patterns of habit.

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Ecological Realism in the History of the Concept of Time

Heidegger’s 1925 lecture course published as the Prolegomena to the History of the Concept of Time is widely considered to be the prequel to Being and Time. Since I consider BT to be a realist work in philosophy, it should not be surprising to find quotations in HCT that support what I call ecological realism. Ecological realism is to be decisively distinguished from philosophical realism. Both realisms agree, doxographically, that the natural world (what Heidegger later calls the Earth) would still exist if humans were wiped off the planet (Of course, this is just common sense, but many commentators seem content to ascribe to Heidegger the nonsensical position of anti-realism in respect to the ontic dependence of the Earth on human disclosure).But ecological realism differs from philosophical realism insofar as the latter accepts the “mind independence” of the Earth but arrives at this position from the starting point of a mind essentially cut-off from the Earth by means of the sense-data “veil”. According to philosophical realism, the only things we know directly are the sense-receptors at the edge of our bodies i.e. what’s called the proximal stimulus. Because they claim we are only in an epistemic relationship with the proximal stimulus, we must therefor “deduce” or “infer” that the distal stimulus exists. And moreover, because of the possibility of hallucination and illusion, we can never be certain that the proximal stimulus veridically corresponds to the distal stimulus. We are thus unable to adequately rebuff the radical skeptic of knowledge.

Ecological realism is different because it assumes that we have a direct epistemic relationship with the Earth by means of our intentional directedness towards the Earth. For ecological realists, the distinction between proximal and distal stimuli is a nonstarter in terms of epistemology. Indeed, Heidegger says in HCT:

When I perceive the chair and say, “The chair has four legs,” the sense of this knowledge according to Rickert is the acknowledging of a value. [However], even with the best of intentions one cannot find anything like this in the structure of this perceptual assertion. For I am not directed toward representations and less still toward value but instead toward the chair which is in fact given. (33)

Indeed,

[Rickert] is prevented from seeing the primary cognitive character of representation because he presupposes a mythical concept of representing from the philosophy of natural science and so comes to the formulation that in representing the representations get represented. But in the case of a representation on the level of simple perception a representation is not represented; I simply see the chair. This is implied in the very sense of representing. When I look, I am not intent upon seeing a representation of something, but the chair. (35)

For ecological realism then, the sense-data hypothesis is mistaken insofar as it begins with the assumption that representations get represented “in the mind”. For Heidegger, we need not make this assumption and indeed, we shouldn’t make it if we are to make sense of the phenomena of perceiving. One might reply by saying that Heidegger is merely assuming what he wants to assume in order to counter the neo-Kantians but why is he justified in assuming that intentionality is directed toward the environment and not toward the proximal stimulus? For one, the Heideggerian position is more parsimonious on the evolutionary and developmental stage because it allows for the possibility of coping behavior without the need for positing an internal consciousness “synthesizing” the proximal data into a percept of the distal stimuli, a processing heavy and thus energy-consuming process. If we look at the earliest progenitors of perceptual systems in unicellular bodies, we can see that the chemical receptors are directly connected with locomotion. The bacterium’s detection of instrumentally relevant chemicals sets off a causal cascade that eventually results in the spinning of the flagellum. In these bodies, there is no possibility of radical skepticism. The epistemic situation is akin to a gear that connects a car’s engine to the tires. Any possibility of perceptual mistake is thus physiological in character rather than epistemological. If we scale these systems up to humans, the same principle applies. We need not assume that the possibility of perceptual breakdown implies the possibility of radical skepticism. Understood from the ecological point of view, perception evolved so as to put us in intimate contact with the Earth. Ecological realism is also committed to the possibility of molar stimuli.

Moreover, in regards to the problem of other minds, philosophical realism assumes

that a subject is encapsulated within itself and now has the task of emphasizing with another subject. This way of formulating the question is absurd, since there never is such a subject in the sense it is assumed here. If the constitution of what is Dasein is instead regarded without presuppositions as in-being and being-with in the presuppositionless immediacy of everydayness, it then becomes clear that the problem of empathy is just as absurd as the question of the reality of the external world. (243)

By exposing the way in which philosophical realism depends on certain unnecessary assumptions about the nature of intentional perceptual systems, we can pave the way for ecological realism as both a metaphysical and epistemological doctrine. Metaphysical, because ecological realism accords with our common sense intuition that the Earth existed before humans and will continue to exist after humans are gone. Epistemological, because it offers a theory of knowledge in terms of opportunities of meaningful behavior.

‘[O]riginally and to begin with,’ one does not really hear noises and sonorous complexes but the creaking wagon, the ‘electric’ streetcar, the motorcycle, the column on the march, the north wind. To ‘hear’ something like a ‘pure noise’ already requires a very artificial and complicated attitude. (266)

This is of course an explication of our being-in-a-world with world understood in terms of significance and meaning. The world is directly meaningful because our affective care-structure compels us towards goals in a teleological fashion. This is of course much more parsimonious with evolutionary theory than any sense-data theory. There is much more to say on this issue, but I will leave the details for another post (and for my master’s thesis!). Also, In Jon Cogburn’s upcoming Fall graduate seminar, we will be exploring this issue of teleosemantics and animal cognition in great detail, so expect a flurry of posts related to these issues in the Fall. I can’t wait!

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The Molar Stimulus: Implications for Visual Science

What is a perceptual stimulus? Many philosophers never ask themselves this question. They often take it for granted that vision science has settled the issue and nothing more needs to be said except that

  1. Visual perception depends on light rays hitting the back of the retina, forming an “inverted image”.
  2. The subsequent “retinal image” is imperfect and ambiguous in respect to “macro properties” since it is more or less “flat” , “upside down”, and registered by messy biological  tissue.
  3. The brain has to “compensate” for the ambiguity by making “hypotheses” about the macroworld. The first stage of processing is the “2D primal sketch”. Next, the brain generates 3D “depth” from the more immediate primal sketch.  Thus, the brain is essentially a Helmholtz “inference machine” from the ground up.
  4. Perceptual experience is what-its-like for the brain to make inferences. Visual experience is thus a simulation grounded by the immediate retinal registration.
  5. Our intentionality is directed towards the simulated inferences rather than the world itself. Visual experience is thus illusionary and generated “internally” by the brain, hence the name internalism.

I take it that this crude picture is more or less an accurate representation of internalism. These presuppositions have become so entrenched, they hardly come up for review. I think it is high time to examine them, particularly in respect to the taken for granted assumptions about what constitutes a perceptual stimulus. The stimulus is often understood as being the immediate rays of light “bumping into” the retina. The retina is said to register the light strictly in terms of the wavelength and intensity i.e. the “primary qualities” of the physical sciences. Thus the retinal image corresponds to “micro” properties rather than molar properties. And because the registration of the retinal image is in terms of micro properties, molar properties like depth, surface, texture, etc. need to be “inferred” and are not directly perceived by the brain. It is said then that the micro properties are what make perception “ambiguous” and prone to error in respect to the macroworld.

But why should we assume that the brain is directed towards micro properties? It seems perfectly reasonable to suppose that the brain is behaviorally sensitive to molar properties specified in the ambient array of light “filling” normal environments. After all, molar properties are where all the action is. Only a programmed computer would be interested in micro properties. Biological bodies are far more interested in what’s going on at the molar level, where temporal events occur. Indeed, as J.J. Gibson points out, “Animals and men [directly] perceive motions, events, episodes, and whole sequences”.

And because all the episodes relevant to survival happen at the molar level (being attacked, hunting, socializing), it’s reasonable to suppose that the brain would have evolved so as to be directly sensitive to molar properties rather than micro properties. And if this is the case, then we need not assume that the brain is a Helmholtzian inference machine at the ground level of visual perception. Contemporary ecological optics has repeatedly demonstrated that molor properties such as depth, surface, and texture are directly specified by the invarient patterns of stimuli resulting from movement through the ambient optic array. The transformations across the retina specify molar properties in virtue of successive and adjacent order in the ambient optic array. Perception is thus capable of “holistic” sensitivity from the bottom up. Natural selection insured that brains developed the ability to be directly attuned to molar properties like motion, not micro properties like wavelengths and intensity. Motion indicates prey or predator. Wavelength indicates nothing unless you are a scientist.

We can thus overturn the five assumptions stated above. Intentionality is directed towards molar properties in the world rather than representations in the head. Because internalists are empirically mistaken about the ambiguity of perceptual stimuli available in the optic array, the absolute bottom-up inference making of classic computational approaches can be rejected as overcompensatory. Sure, the brain probably does make many inferences, particularly at higher-level stages in visual processing. But a complete Helmholtz machine? Unlikely. The availability of molar information in the optic array “ripe for sampling” obviates the need for a bottom-up inference from the micro to the molar. Our genetics ensure that nervous tissue is behaviorally sensitive to molar properties in the environment. This means that the “eternal now” of instantaneous registration is mythical and purely heuristic. Perceptual registration is temporally extended in virtue of its intentional directedness towards molar properties. We need to thus think about the brain in terms of a temporally extended coherence or “resonance” that is behaviorally sensitive to molar properties. This requires rethinking the constitution of perceptual stimuli and the evolutionary development of sensorimotor systems.

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The Myth of Sensory Immediacy – Why Berkeley Was Wrong

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Theories are often supported by unquestioned assumptions. One of the oldest unquestioned assumptions in philosophy concerns the nature of perceptual stimuli, namely, that sense-data are immediately perceived and that sensation consists in the sequential processing of  “motions” immediately pressed upon the eye. Originating in Plato’s Theaetetus, this idea reached maturation in Descartes and was then taken up by Locke under the concept of primary and secondary qualities. According to these thinkers, sensible ideas (sense-data) are immediate impressions upon the eye which communicate the motion of light particles through the nerve conduits so that they may be processed and deposited onto the internal mental theater for subjective viewing. It is important to note that the conduit metaphor assumes that perception can only perceive the atomic sequence of impacts upon the eye; any nonimmediate mental perception is the result of “inference”. In other words, there is a “bottleneck” of immediacy that cannot be overcome without higher-order cognitive acts. Moreover, sense-data are private in that the primary qualities “appear” differently for different people in accordance with their individuality.  The logic of this conduit metaphor was radicalized by Berkelely in his extreme sense-data empiricism. In the First Dialogue, he writes:

Philonous. It seems then, that by sensible things you mean those only which can be perceived immediately by sense.

Hylas. Right.

Phil. Doth it follow from this, that though I see one part of the sky red, and another blue, and that my reason doth thence evidently conclude that there must be some cause of that diversity of colours, yet that cause cannot be said to be a sensible thing, or perceived by the sense of seeing?

Phil. This point then is agreed between, that sensible things are those only which are immediately perceived by sense. You will further inform me, whether we immediately perceive by sight any thing beside light, and colours, and figures: or by hearing any thing but sounds: by the palate, any thing besides tastes: by the smell, besides odours: or by the touch, more than tangible qualities.

Phil. Sensible things therefore are nothing else but so many sensible qualities [immediately perceived], or combinations of sensible qualities.

Our discourse proceeded altogether concerning sensible things, which you defined to be the things we immediately perceive by our senses. Whatever other qualities therefore you speak of, as distinct from these, I know nothing of them, neither do they at all belong to the point in dispute.

As a good empiricist, Berkeley radicalized the logic of the conduit metaphor for visual perception. If there is nothing “in” the mind-container other than impressions formed by the immediate perception of sensible things, and if sensible things cannot exist without a perceiving mind, then we have no rational recourse for knowing anything about an extrasensory material world composed of primary qualities not dependent on the mind. Thus, the ultimate substance of reality is Mind or spirit, for we can never escape the confines of our mental container.

The essence of the conduit/container metaphor consists in understanding the perceptual process in terms of an immediate communication of sense-data across the nerve-conduits into the “container” or “theater” of the mind. Accordingly, the very nature of the perceptual stimulus ensures that the mind can never rationally proceed beyond the causal immediacy of private sense-data. Because the perceptual stimulus is assumed to consist of immediate impressions upon the retina, any perception of motion must be inferred from the two-dimensional patterns of light, which are then transduced into sense-data. For Berkelely, the radicalization of this logic leads to the proposal that we have no rational recourse for getting “outside” of the internal theater of sense-data, for what we “perceive” is not the primary real, but rather, the secondary quality of “how it appears” subjectively.

Upon reflection however, we can see that the flatness or “immediacy” of sensory input is usually presupposed only after thinking about perception in terms of a frozen snapshot of reality. Ecological information, however, does not exist exclusively in an instantaneous slice of time for, as J.J. Gibson points out, “Animals and men [directly] perceive motions, events, episodes, and whole sequences” (1966, p. 276). Thus, the information we perceive in the environment has both successive and adjacent order. For Gibson, it is a mistake to think of persisting patterns as being a separate stimulus; biologically speaking, “Transformations of pattern are just stimulating as patterns are…motion is immediately detected by animals, not secondarily deduced from change of position”( ibid., p. 40). Accordingly, the brain is not in the business of continuously constructing a mind bogglingly detailed phenomenal model from spots of sensations differing in brightness and color. If this were true, Gibson sardonically notes that “the fact of perception [would be] almost miraculous”. Instead, Gibson theorizes that the nervous system directly “picks up” or behaviorally “resonates” to the ecological information available in the environment, particularly in respect to changes in the layout of surfaces, changes in the color and texture of surfaces, and changes of existence of surfaces. As Mark Rowlands nicely puts it,

information is simply optical structure-together with the deformation in this structure generated in a nomothetic way from the environmental layout and events. This optical structure is not similar in any way to the environment, but it is specific to it. That is, optical structure is nominally dependent upon environmental structure. Because the structure in the optic array is specific to its environmental sources, an observer whose perceptual system detects some optical structure is therefore aware of what this specifies. Thus, the perceiver is aware of the environment not the array. Therefore, once we describe the input for perception in terms of a structured optic array, we are committed to the idea that there is enough information directly available in the organism’s visual input to give that organism useful knowledge about the nature of its environment. Postulation of additional information processing would, to this extent, be superfluous. (1995, p. 9)

The logic of Gibsonian information processing goes counter to the thesis of radical sensory immediacy. Under the Gibsonian framework, perception is not constituted by the processing of sense-data through the bottleneck of retinal immediacy. Instead, the perceptual system is capable of a first-order perception of whole sequences in the environment. By proposing that the transformations of pattern within the ambient optic array contain both sequential and adjacent order, the notion that perception consists of immediate detection and transduction of motion across the two-dimensional retina loses its status as an unquestioned assumption. Accordingly, the Gibsonian framework argues that perception is grounded by ecological information, not sensory immediacy. And because ecological information is temporally extended, the classic model of immediacy is overcome by supposing that animals are capable of directly resonating to such information. As it turns out then, we are not trapped within the theater of our minds; access to reality is quite pedestrian.

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