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Perception And Reality

by Bill Meacham on July 19th, 2015

Do we see reality as it is? The fact that we are subject to perceptual illusion leads some thinkers to assert that we don’t. Instead, we see (or taste or feel, etc.) an illusion concocted by our brains. Donald Hoffman, Professor of Cognitive Science at the University of California at Irvine and a respected researcher, is a popularizer of this view. A couple of recent videos, one on the Science Channel,(1) and another on TED,(2) are entertaining expositions of his thesis that our experience is misleading.

Take this picture, for instance, one of many on his website:


The figure on the left contains various grey patches. Two of them, corresponding to A and B in the figure on the right, appear to be different but are actually identical greys; a photometer would find them to be the same. Hoffman takes this as evidence that the cognitive aspect of our perception (he calls it “visual intelligence”) constructs the greys that we perceive.(3)

The idea that the world we encounter in our everyday experience is not the real world is not new. Ancient Indian philosophy speaks of the world as Maya, illusion, which conceals the true nature of reality.(4) Plato likens us to prisoners in a cave and likens the things we experience to shadows thrown on a wall. The philosopher is one who breaks his (or her) chains and ventures out into the real world to perceive reality truly.(5) Kant said that things in themselves are unknowable; all we know through our senses is the world of phenomena.(6)

What Hoffman brings to the table is not only a wealth of experimental evidence but a plausible account of how we got this way. His thesis is that our perceptual apparatus is wired evolutionarily, not to perceive reality accurately, but to enhance our genetic fitness. What counts is not how well we see reality as it is, but how well what we see helped our ancestors stay alive long enough to mate and have children. And what we see is shaped by “tricks and hacks,” as he says(7), not accuracy.

This account is not merely a “just-so” story.(8) Hoffman has conducted some mathematically rigorous computer simulations that show that creatures that employ strategies tuned to utility outcompete those that employ strategies tuned to objective reality.

Here is a simplified version. You construct a series of simulated habitats, each of which has some quantity of food and water. Then you construct two creatures that will look at the habitats and choose one to occupy. One creature, the truth seeker, looks at the exact quantities of both food and water; it has an accurate perception of reality. Another creature, the simple hacker, just looks for the greatest amount of food and ignores water; it uses a trick, not a fully accurate perception. The truth seeker takes more time and energy to gather its information and make a choice than the simple hacker. The simulation repeatedly pits the two creatures against each other in a variety of habitats. It turns out that the simple hacker occupies the better habitats more quickly than the truth seeker. In other words, it outcompetes the truth seeker. Accurate perception of reality turns out not to be an optimal strategy.(9)

Hoffman and his colleagues have performed many far more complex simulations, pitting not just these two strategies against each other but yet another as well. The truth seeker embodies what they call a naive realist strategy; its perceptions fully match what really exists. The simple hacker embodies a critical realist strategy; its perceptions are limited but still reflect some truth about reality. Both are homomorphic to reality; that is, both have the same shape or structure as reality. The critical realist strategy is just less finely grained than the naive realist one. Hoffman proposes yet a third strategy, which he calls the interface strategy, in which perceptions are not homomorphic to reality. In the simulations, the interface strategy outperforms both of the others. Hoffman and his colleagues conclude that “natural selection does not always favor naive realism or critical realism. … In many scenarios only the interface strategy survives.”(10) In other words, it is entirely possible that our perceptions bear no resemblance to reality at all! (To be clear, Hoffman does not say that the interface strategy always or necessarily wins, only that it can. And that a lot more research is needed.)

So the claim, supported by some evidence, is that it is possible that our perceptions bear no resemblance to reality at all. But Hoffman, in his popular lecture, goes further. He claims that it is not just a possibility but a fact that they bear no resemblance. He says, “There’s something that exists when you don’t look, but it’s not spacetime and physical objects.”(11) And “When I have a perceptual experience that I describe as a red tomato, I am interacting with reality, but that reality is not a red tomato and is nothing like a red tomato.”(12)

Hoffman goes too far here. How can he possibly know that reality bears no resemblance to our perceptions? By his own admission, we have no contact with reality—what Kant calls the Ding an sich, the thing in itself—at all. So there is no way to make a comparison.

What we can compare is not experience with reality, but some experiences with others. Consider the visual illusion of patches of grey above. The reason we think our perception is illusory is that it doesn’t agree with what a photometer tells us. But we know what a photometer tells us only through our experience!

Try this: print this page and then cut out the two patches in question and place them side by side. In that position they will look the same. If you have a photometer, measure them, both in context and side by side. In all cases they will measure the same. You can go to the website of Edward A. Adelson, the originator of the illusion, to see more evidence for their sameness.(13)

There is a reason that we consider our experience of the photometer and our experience of the patches viewed side by side more veridical than our experience of the patches in context. It is simpler and more coherent to assume that the grey colors stay the same and our perception varies by context rather than that the colors actually change when the context changes. And the former assumption leads us to make more successful predictions.

What we take as physical reality is what Willard Van Orman Quine calls a “cultural posit.” His account is picturesque but informative:

As an empiricist I continue to think of the conceptual scheme of science as a tool, ultimately, for predicting future experience in the light of past experience. Physical objects are conceptually imported into the situation as convenient intermediaries—not by definition in terms of experience, but simply as irreducible posits comparable, epistemologically, to the gods of Homer. Let me interject that for my part I do, qua lay physicist, believe in physical objects and not in Homer’s gods; and I consider it a scientific error to believe otherwise. But in point of epistemological footing the physical objects and the gods differ only in degree and not in kind. Both sorts of entities enter our conception only as cultural posits. The myth of physical objects is epistemologically superior to most in that it has proved more efficacious than other myths as a device for working a manageable structure into the flux of experience.(14)

Similarly, the myth of reality as homomorphic, for the most part, to our experience is believable just because it works so well for us. Optical illusions reveal, not flaws in our perception, but how well our visual system is adapted to reality under standard conditions.(15)

(To be fair, Hoffman does have a more complete argument for his view of the relationship between experience and reality, which he calls “Conscious Realism,”(16) but a full discussion of that is a topic for another time.)


(1) Hoffman, “Can We Handle The Truth?”

(2) Hoffman, “Do we see reality as it is?”

(3) Hoffman, “Constructing Shades of Grey.”

(4) Wikipedia, “Maya (illusion).”

(5) Plato, The Republic, 514a–520a.

(6) Kemerling, “Kant: Experience and Reality.”

(7) Hoffman, “Do we see reality as it is?” time 11:45.

(8) Wikipedia, “Just-so story.”

(9) Mark, et. al., “Natural selection and veridical perceptions” pp. 505-506.

(10) Ibid., p. 513.

(11) Hoffman, “Do we see reality as it is?” time 16:22.

(12) Ibid., time 16:59.

(13) Adelson, “Checker Shadow Illusion.”

(14) Quine, “Two Dogmas of Empiricism,” p. 41.

(15) Bach, “Optical Illusions & Visual Phenomena.”

(16) Hoffman, “Conscious Realism and the Mind-Body Problem.”


Adelson, Edward H. “Checker Shadow Illusion.” Online publication as of 19 July 2015.

Bach, Michael. “Optical Illusions & Visual Phenomena.” Online publication as of 19 July 2015.

Hoffman, Donald. “Can We Handle The Truth?” Online publication as of 16 July 2015.

Hoffman, Donald D. “Conscious Realism and the Mind-Body Problem.” Mind & Matter Vol. 6(1), pp. 87–121. Online publication as of 15 July 2015.

Hoffman, Donald. “Do we see reality as it is?” Online publication as of 10 July 2015.

Hoffman, Donald. “Constructing Shades of Grey.” Online publication as of 16 July 2015.

Kemerling, Garth. “Kant: Experience and Reality.” Online publication as of 17 July 2015.

Mark, Justin T., Brian B. Marion, Donald D. Hoffman. “Natural selection and veridical perceptions.” Journal of Theoretical Biology #266 (2010), pp. 504-515. Online publication as of 15 July 2015.

Plato. The Republic. In Plato: The Collected Dialogues. ed. Edith Hamilton and Huntington Cairns. New York: Pantheon Books, 1963.

Quine, W. V. “Two Dogmas of Empiricism.” The Philosophical Review, Vol. 60, No. 1 (Jan., 1951), pp. 20-43. Online publication as of 31 March 2014.

Wikipedia. “Just-so story.” Online publication as of 17 July 2015.

Wikipedia. “Maya (illusion).” Online publication as of 17 July 2015.

From → Philosophy

  1. Thanks for the post, Bill. I had a similar reaction to Hoffman’s TED talk when it came out a while back. I find it ridiculous to seriously propose the truth of a sentence like “When I have a perceptual experience that I describe as a red tomato, I am interacting with reality, but [[ that reality is not a red tomato and is nothing like a red tomato.]]” as Hoffman did in his talk. I’d say the bracketed part would be more correct as: “that reality must be in one sense a red tomato and therefore something like a red tomato, but quite surely far more than a red tomato.”

    I see all this stuff most simply resolved in understanding the embedding nature of ontologies, which Hoffman seems to neglect to the point of making obviously false statements, and not just on this front. If he could see more clearly that even “I am interacting with reality” is itself problematic in that it jumps across chasms of ontological distinction which the word “interacting” just can’t be up to the task of bridging, he might be able to resolve some of the problem.

    The reality we all want to point to has the special role of being everything which is. It would seem to be, by our definition of course, ontologically fundamental or defined as the most embedding of all ontological strata. But, depending on the more inclusive interpretation of “reality”, it could also be defined as trans-stratum. For example, if I imagine a pink elephant which floats on clouds, from the narrow definition of reality, that elephant is not real. But from the more inclusive definition, it is real in the ontological stratum of human imagination, albeit not real in the stratum of natural human physical experience.

    Thus for me, the key thing about understanding reality is more about clarifying our ontology of choice for the conversation, and less about those absolute definitions of reality which simply don’t work very well. Without a doubt, everything is real. The meaningful question is, real in what ontological strata?

    To apply this conception back to the post’s topic, Hoffman goes astray in his premises by presuming some referenceable absolute reality, which as you pointed out is utterly inaccessible as itself, both experientially and epistemologically. We can generate a version or model of reality using our knowledge and imagination, and even propose it to be absolute and fundamental. But none of this makes the “real reality” so. There is no completeness available to the proposals we might make about the reality we assume is out there beyond our reach. By its very definition, any statements we make about it must be incomplete. That’s what it means to be finite, which is also what it means to be at all.

  2. Leonard permalink

    Very interesting post, Bill. Thanks!

  3. Carl Ehlert permalink

    There is an interesting remark that my psychologist wife often quotes which is “We do not see the world as it is but as we are.” The “we” in this phrase can be interpreted as the collective we meaning human kind or as the individual herself trying to make sense of her world. It is interesting to note that while psychology denies the concept of “normal” prefering to speak of a spectrum of different understandings or positions concerning reality they still talk of ,mental illness – bi-polar disorder, manic- dpressive disorder -post tramatic stress etc. – as being misperceptions of reality. This would imply that while there are a broad range of “interpretive realities” that we accept there are others that seem to fall outside or miss the mark in some significant way. Of course, we are not necessarily speaking of physical reality -the so called “real world” – but instead we are referring to “social reality” – the created world of language, symbol and relationship. This brings up my second quote which is “we create the world we live in and then live in the world we create.” I am not sure where this comes from. I may have made it up??? The point is does it really matter if what I perceive as red and what you perceive as red are the same thing as long as we react appropriately as in stopping at a red light? More importantly, if you believe that some idea or super being or beings is upholding the perceived reality and I do not does this mean we must turn against each other, hate each other, kill each other? History would seem to answer with a resounding yes but what interests me is if I accept that I create my world then why do I assume that it is the one true reality while your created world is not simply false but morally wrong? Why do I hold so tightly to my version of reality? Why is it so important? Tis a mystery!

  4. El Gee permalink

    My study of Stan Grof’s work has given me a psychological perspective on the cave allegory that intensifies its philosophical, mystical significance. Analogizing the cave to the womb leads me to comparing Stan’s phenomenology of the birth process in terms of what he calls “basic perinatal matrices.” The prisoners begin in amniotic ignorance, are wrenched by the onset of uterine contractions, struggle up through the birth canal, and finally emerge. Mystical rebirth is a transcendental reiteration of original birth.

    Plato’s pairing the divided line with the cave allegory emphasizes a ladder-like path to mystical epiphany, which he reiterates in the Symposium. The validity of Plato’s description is attested by Plotinus, when he says, “Using the method of Plato” he followed the path to transcendence.

    Another comparison I make with the cave allegory is the 23rd psalm, where the valley of the shadow of death suggests the birth canal. The rod of Asclepius protects. The birthed child, in a desert culture, is not bathed in water, but anointed with cleansing oil.

    The cave allegory/divided line also is recalled by Paul’s reference to seeing “through a glass darkly.” On emerging from the cave, one can first look only at reflections, before seeing “face to face.”

    Thanks for provoking my reflection.

  5. Very fascinating blog post! Thanks a lot. You did a good job of connecting science and philosophy there, cutting out a manageable piece from a gigantic subject.

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