After a Taste-Bud Hiatus, Experiencing Candy Like a Six-Year-Old

I used to blog quite a bit about weird aspects of sensory experience, back when my central research interest concerned the vagaries of introspection and the strange things people say about their streams of experience. (See a few sample posts; some articles; two books.) I thought I'd share another today -- something striking to me -- though actually not that weird, I suppose.

About a month ago, I accidentally bit down hard on an unpopped popcorn kernel, "bruising" the teeth on the left side of my mouth. (Yes, that's a thing. My dentist tells me nothing is broken or cracked; it just needs time to heal.) It was remarkably painful to chew on that side, and for weeks I chewed entirely on the right side of my mouth, barely even letting food drift to the left side. Last week, I resumed gently chewing on the left again -- just soft things, carefully, experimentally. Having dessert one night, I was suddenly struck by how much sweeter the dessert tasted on the left side than on the right side. Remarkably sweeter. Different enough that the fact really jumped out at me, though I wasn't at all expecting or looking for it.

I was eating an "orange slice" candy. You know, one of these guys:

On the right side of my mouth, the candy was blandly sweet with a simple citrus flavor. On the left side, I experienced the candy as vividly sweet, zinging with orange. The contrast persisted as I moved the mass of candy around in my mouth. When I shifted the bulk to the right, it seemed to instantly lose flavor, like a piece of gum chewed too long. When I shifted it back to the left, the flavor brightened again.

I experimented with other candies over the next few days: lemon and lime slices, chocolate, peppermint sticks. I consistently found the left side sweeter than the right -- and not only sweeter, but also more vividly flavored in other ways. However, I found no similarly noticeable difference for savory flavors, or tea, or pure salt, straight lemon juice, or many of the other things I have eaten since. The effect was mostly or entirely limited to sweetness only, and the associated flavors of the sweet things.

I remember loving fruit slice candies when I was six. I would savor them for fifteen minutes, driving my parents nuts, who had to wait for me at the end of meals. (Now I tend to wolf down desserts: See my defense of dessert-wolfing.) The flavor of the orange slice resonated with my memories of youth. It was like my taste buds -- or the related sensory regions in my brain -- were six years old again. It seemed to me that the orange slice tasted to me now, on the left side of my mouth, in that amazing way it had tasted to me as a child, and then when I shifted it to the right side, it fell back into the blandness that I have since become accustomed to.

I'm not sure why the effect was limited to sweetness. In general, taste sensitivity declines with age, but the decline seems to be as strong for salty, savory, and bitter tastes as for sweet ones. My taste experience has probably dulled in multiple respects. Why sweetness only should rejuvenate, I have no idea -- even more confusingly, not simple sweetness only but the more complex flavors tangled up with sweetness, such as chocolate and sweet orange.

A week later, I find that the effect is still present, though diminishing. I want the vivid sweetness back! The experience acutely reminds me of how much of what we vividly experience recedes into a fog with ageing. A comparison point: I remember getting glasses as a teenager after years of slightly blurry vision and loving how sharp the world became. Now even the best prescription I can find will never make the world that sharp. I also feel that when I read fiction I don't quite as vividly imagine the scenes as I used to.

Middle age has its compensating advantages. I'm mellower, more settled. Even sensorily, things are open to me that weren't before: Presumably because of my diminished taste sensitivity, I can enjoy bitter coffee and sharp cheese. But the hiatus from left-side chewing, followed by some fleeting new candy raptures, has given a sharp new tang to my thoughts about sensory loss with age.

[image source]

The Peak-End Theory of Dessert: A New Philosophy of Wolfing

My daughter Kate eats desserts slowly -- has done so as long as I can remember. She is what I'll call an extreme savorer. In other words, she is a completely irrational moral monster, as I will now endeavor to show.

I'll admit that on a superficial analysis, Kate's approach to dessert appears wise. Someone bakes brownies. Everyone in the family receives a brownie of equal size. My son's is gone in a flash. My wife and I eat ours moderately quickly. Kate delicately saws off an edge and puts it on her tongue, waits a while, saws off another edge. Ten, fifteen minutes later, Kate is still enjoying her brownie while the rest of the family watches enviously.

At such moments I think, "Why don't I slow down and savor my dessert like Kate does? She obviously derives much more sweet pleasure from her slow ways!" Several days later, of course, it's "Yum, ice cream sandwiches!" munch munch munch and once again after my share is gone I find myself envying Kate's slower pace.

[Kate at work on a Trader Joe's dark chocolate peanut butter cup]

Now I'd rather not see myself as quite as terribly irrational as this pattern suggests. Fortunately, being well-trained in both philosophy and psychology, I have a wealth of theoretical resources from which to concoct a plausible justification of pretty much anything. Our task for today, then, is to demonstrate that I am right and Kate is wrong.

We need a philosophy of wolfing.

The Peak-End Rule

In a classic series of studies, Daniel Kahneman, Donald Redelmeier, and collaborators found that in retrospectively evaluating negative or painful experiences, people tend to disregard the duration of the experience. Instead, people evaluate their experiences mostly based on how the experiences felt at their peak and how they felt at the end.

Some of the results are startling: For example, in one experiment, ordinary colonoscopy patients were either given standard painful colonoscopy procedures or instead the same standard painful procedures plus the extra (but less severe) discomfort have having the colonoscope rest in their rectum unmoving for an additional three minutes at the end. Patients reported their pain levels in real time throughout the procedure. The peak level of pain was the same in the two groups, as was the overall pain during the main part of the procedure. Consequently, patients in the second group had more total pain: the pain of the main procedure plus an extra three minutes of discomfort. Nonetheless, patients in the second group retrospectively reported having experienced less pain, and they reported a less negative overall attitude toward the procedure.

What's more, the patients acted accordingly: Over the next five years, patients who otherwise were predicted to have a low propensity to return for another colonoscopy (patients with less past history of colonoscopies and no detection of abnormalities) were more likely to return for another colonoscopy if they were in the experimental group who had received the extended procedure than if they were in the control group who had received the standard procedure.

Kahneman and colleagues found similar results with participants asked to hold their hands in painfully cold water. Participants held one hand for 60 seconds in water that was 14.1 degrees Celsius (painfully cold but not damaging) (Procedure A) and also, either before or after, held their other hand for 60 seconds in water that was the same 14.1 degrees C and then kept it in the water for an additional 30 seconds while the temperature was slowly raised to 15.2 degrees (still uncomfortably cold) (Procedure B). When told that they could choose either Procedure A or Procedure B for the third trial, most chose Procedure B. They chose more pain over less.

According to the "peak-end rule", the retrospective evaluation of either a positive or a negative experience is an average of the quality of the experience at its positive or negative peak and the quality of the experience at its end, with little regard for duration. Despite the fame of this rule (including in guides to managing one's business, etc.), it isn't as thoroughly studied as one might expect, and findings remain mixed.

Still, let's assume that something close to the peak-end rule is true about the enjoyment of desserts: How fondly you remember your dessert is a function mostly of the average of your most pleasant bite and your last bite.

Wolves Will Remember Dessert More Fondly

It should now seem plausible that if you wolf down your dessert, you will remember it more fondly.

The peak will be better: Instead of modest bite after modest bite of moderate pleasure, you will experience the unrestrained joy of a giant bite of popping deliciousness all at once. Maybe the best part is the cherry atop the icing. The wolf will get that great mouthful of cherry, icing, and cake all at once, while the savorer will have no such moment of sudden decadent indulgence.

The end will also be better: We grow weary of even the best things over time. Although the twentieth bite of chocolate is still good, it's never as wonderful as the first few bites. By bite twenty your mouth is accommodated to the sweetness, and the pleasure is only a temperate, lingering continuation. The last bite will be more flavorful if you don't take too long in getting around to it.

Furthermore, there is a joy in not holding back. What could be more childish fun than just diving in, biting the whole head off the Easter bunny or shoving a great spoonful of cherry, whip cream, and cake right into your mouth? The savorer's experience will always be tainted with the slightly unpleasant feeling of self-restraint.

This figure compares the Wolf's and the Savorer's dessert experiences over time:

[click to enlarge and clarify]

Although the savorer enjoys dessert longer and the total sum pleasure (represented by the total area between the line and the x axis) might be larger, both the peak and the end are higher for the wolf. If peak-end theory is correct and duration is mostly ignored, then looking back on the dessert, the wolf will think, "wow, that was great!" while the savorer will think "okay, that was pretty good".

"But Peak-End Reasoning Is Irrational!"

Look, I know what you savorers are thinking. It's irrational to choose according to the peak-end rule. It doesn't make sense to tack some extra pain at the end of a colonoscopy just so that it doesn't conclude on quite so vividly painful a note. You should want to immediately withdraw your hand from the cold water rather than keeping it immersed longer while the water warms slightly. We should want less total pain, not more. It's a mistake to disregard duration as much as we do. And the wolfer, you think, is making exactly that mistake, while the savorer rationally sacrifices peak pleasure for enduring pleasure. If she does it rightly, the savorer derives more total joy from her dessert, wisely shaping her behavior to maximize not the peak or the end but instead the entire integral under the line.

This argument errs in two ways.

First, part of the pleasure of dessert is remembering it fondly and anticipating the next one. (Colonoscopies might differ in this respect.) If the wolfer sustains a more positive attitude toward dessert due to his memory of a great peak and a good end, the wolfer multiplies that pleasure in recollection and planning. "Wow, do you remember how great those brownies were? Let's make more next week!" Smelling the next batch in the oven, or putting the Swiss chocolate in his shopping cart, the wolf rekindles his greater bliss.

Second, a life with peaks and valleys is overall better and more choiceworthy than a life at steady medium good. Here I side with Nietzsche against the Stoics. This is, I think, especially true on the positive side, when the valleys are not too low. (I would not wish suicidal depression on anyone.) Given a choice between 2 2 2 2 2 and 1 0 10 -1 0 -- both summing to ten units of pleasure -- give me the second every time. Give me the wolf's sloppy peak bite off the top of the sundae, even if it's finished soon, over the savorer's monotonous, slow licking.

Envy Becomes Pity and Maybe Forgiveness

Now that I am thinking about these matters clearly, I see that our envy of Kate's slow ways is misplaced. As we sit there watching her still eating her brownie, we envy her because we imagine the pleasure of wolfing down the brownie that remains before her. But we should pity Kate instead: In her faux wisdom she will never know that wolfish pleasure. Not only does she deprive herself, but she negligently or recklessly or even intentionally (as part of her pleasure?) teases and torments us wolves, which makes her choice not only prudentially but morally wrong.

But Kate, I promise not to judge you too harshly -- I will forgive you, even! -- if you will share that last bit of the peach cobbler with me. Pretty please?

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If you enjoy my blog, check out my recent book: A Theory of Jerks and Other Philosophical Misadventures.

Why the Epistemology of Conscious Perception Needs a Theory of Consciousness

On a certain type of classical "foundationalist" view in epistemology, knowledge of your sensory experience grounds knowledge of the outside world: Your knowledge that you're seeing a tree, for example, is based on or derived from your knowledge that you're having sensory experiences of greens and browns in a certain configuration in a certain part of your visual field. In earlier work, I've argued that this can't be right because our knowledge of external things (like trees) is much more certain and secure than our knowledge of our sensory experiences.

Today I want to suggest that foundationalist or anti-foundationalist claims are difficult to evaluate without at least an implicit background theory of consciousness. Consider for example these three simple models of the relation between sensory experience, knowledge of sensory experience, and knowledge of external objects. The arrows below are intended to be simultaneously causal and epistemic, with the items on the left both causing and epistemically grounding the items on the right. (I've added small arrows to reflect that there are always also other causal processes that contribute to each phase.)

[apologies for blurry type: click to enlarge and clarify]

Model A is a type of classical foundationalist picture. In Model B, knowledge of external objects arises early in cognitive processing and informs our sensory experiences. In Model C, sensory experience and knowledge of external objects arise in parallel.

Of course these models are far too simple! Possibly, the process looks more like this:

How do we know which of the three models is closest to correct? This is, I think, very difficult to assess without a general theory of consciousness. We know that there's sensory experience, and we know that there's knowledge of sensory experience, and we know that there's knowledge of external objects, and that all of these things happen at around the same time in our minds; but what exactly is the causal relation among them? Which happens first, which second, which third, and to what extent do they rely on each other? These fine-grained questions about temporal ordering and causal influence are, I think, difficult to discern from introspection and thought experiments.

Even if we allow that knowledge of external things informs our sense experience of those things, that can easily be incorporated in a version of the classical foundationalist model A, by allowing that the process is iterative: At time 1, input causes experience which causes knowledge of experience which causes knowledge of external things; then again at time 2; then again at time 3.... The outputs of earlier iterations could then be among the small-arrow inputs of later iterations, explaining whatever influence knowledge of outward things has on sensory experiences within a foundationalist picture.

On some theories, consciousness arises relatively early in sensory processing -- for example, in theories where sensory experiences are conscious by virtue of their information's being available for processing by downstream cognitive systems (even if that availability isn't much taken advantage of). On other theories, sensory consciousness arises much later in cognition, only after substantial downstream processing (as in some versions of Global Workspace theory and Higher-Order theories). Although the relationship needn't be strict, it's easy to see how views according to which consciousness arises relatively early fit more naturally with foundationalist models than views according to which consciousness arises much later.

The following magnificent work of art depicts me viewing a tree:

[as always, click to enlarge and clarify]

Light from the sun reflects off the tree, into my eye, back to primary visual cortex, then forward into associative cortex where it mixes with associative processes and other sensory processes. In my thought bubble you see my conscious experience of the tree. The question is, where in this process does this experience arise?

Here are three possibilities:

Until we know which of these approaches is closest to the truth, it's hard to see how we could be in a good position to settle questions about foundationalism or anti-foundationalism in the epistemology of conscious perception.

(Yes, I know I've ignored embodied cognition in this post. Of course, throwing that into the mix makes matters even more complicated!)

Flying Free of the Deathbed, with Technological Help

Today marks the third year since the death of my father, Kirkland Gable. (Some memories of him here.) I now better understand than I once did why the ancient Confucian tradition recommends three years' mourning for one's parents. To my surprise -- since we had only been in contact about once a month before his death -- I find myself almost every day still thinking about his absence.

My father spent the final twenty years of his life severely disabled and often bedridden. Among his many maladies, he suffered from severe Chronic Regional Pain Syndrome in one foot, which meant that he was in constant pain which would be seriously aggravated, sometimes for weeks, from even mild exertion, such as ten minutes' walking, or jostling the foot too much during sleep or while in a wheelchair. It was, I believe, ultimately the CRiPS that killed him, through the side effects of long-term narcotics and the bodily harm from spending years almost immobile in bed.

I have often wished, during his final years, that we could have freed him from his horrible bed. I've tried this in imagination many times, attempting to write it up as a science fiction story. But the story never seems to come out right. Today, instead of the story I can't yet write, let me discuss a technological innovation that I think would be interesting for people who are bedridden.

The core idea is simple and would be easy to implement. Probably, it is already being implemented somewhere. (Links and info welcome!) Equip an able-bodied volunteer, the "Host", with a camera above each eye and a microphone by each ear. Equip the bedridden person, the "Rider", with VR gear that immersively presents these audiovisual stimuli to Rider's eyes and ears. Also equip Rider with a microphone to speak with Host, directly into Host's ear. Now send Host on a trip. During this trip, let Host be guided mainly by Rider's expressed desires, going where Rider wants, looking where Rider wants to look, stopping and listening where Rider wants to stop and listen. Unlike VR tours as they currently exist, Host can interact with and alter the environment in real time. Rider could have Host lift a flower and turn it in their hands, then cast the flower into a stream and watch it drift away. Host could purchase goods or services on Rider's behalf. Host could conduct a conversation through Rider, interacting with locals by having Rider speak Host's words verbatim.

(In the psychology literature, speaking the words of another immediately upon hearing them quietly projected into your ear is called "conversational shadowing". In his career as a psychologist, my father was involved in some early shadowing studies. Shadowing can be surprisingly fast and smooth once one gets the hang of it, with utterances almost simultaneous as the host half-anticipates the rider's next word.)

A more ambitious Host-Rider setup would employ VR gloves. As I imagine it, Rider and Host wear matching gloves. These gloves are synchronized to move in exactly the same way -- of course with quick escape overrides and perhaps with Rider's motions damped down to prevent overextension or bumping into unseen obstacles near the bed. This would take some excellent technological chicanery with good motion tracking (Nintendo Wii, improved) and some way of restricting or guiding the movements of the gloves on each end, perhaps using magnetic fields, so that when Rider wants to move a hand on vector W and Host wants to move it on vector V, the result is some compromise vector (barring safety override). An intuitive collaboration would be necessary between Rider and Host, and gentle, predictable movements. With practice, I think it would not be unfeasible, at least in safe and simple environments, for Rider to feel as though it is almost their hands that are moving in the virtual environment. This could be further enhanced with tactile feedback -- that is, if pressure sensors in Host's gloves communicated with actuators in Rider's gloves that exerted corresponding pressures in corresponding locations.

(Here, compare the Rubber Hand or Body Transfer Illusion. I have been a participant in some body transfer experiments and have informally conducted others at home with friends and family. It is amazing how flexible one's sense of one's bodily shape, position, and boundaries can be, given suggestive feedback!)

A final, expensive, risky, and much more conjectural step here -- probably a step too far -- would involve equipping Host and Rider with helmets with brain-imaging technology and the capacity for Transcranial Magnetic Stimulation (or some other ability to directly stimulate or suppress brain activity). For example, for a fuller tactile experience, activity in Host's primary somatosensory cortex could be tracked, and a vague, faint echo of it could be stimulated in matching areas in Rider's cortex. One wouldn't want too much synchrony, and anyhow brains differ somewhat in their organizational structure, even in fairly similarly structured regions like somatosensory cortex. Also, of course, you wouldn't want much motor signal going down through efferent nerves into the Rider's body, making Rider move around in the bed. Also, current brain imaging technologies, even if we imagine portable versions of them, wouldn't be spatiotemporally sharp enough to do a proper job of it. But still, a dim, vague signal might be very suggestive for an otherwise well-harmonized, collaborative Host and Rider, in a rich environmental context with very clear cues and expectations.

I won't conjecture about, say, attempting to match activity in emotional regions or associative cortex. Conjecturing about a high degree of match between different people's brains is both neurophysiologically unrealistic and possibly too threatening to the autonomy of Host and Rider -- though of course there are dark, interesting, far-future science-fictional possibilities there.

Let's bracket, then, this last conjectural step with brain imaging and brain stimulation, and focus just on the VR experience with audiovisual input, shadowing, and matching-motion gloves -- all in a positive, harmonious, and non-exploitative relationship with a host. I think that would be pretty cool, and near- to medium-term technologically achievable. If it plays out right, it might give some bedridden people a chance to explore the world beyond their bed in a much more vivid, engaging, and interactive manner.

My father was both a psychologist and an inventor. In 1995, when he was first diagnosed with cancer, he had been wanting to go to Hong Kong, and he had to cancel the trip to attempt a bone marrow transplant. He never did make it to Hong Kong. I wish I could bring him back, build some of this technology with him, then take him there.

[image source]

Minds Online Conference

is cooking along. You might want to check out this week's lineup, on Perception and Consciousness:

Nico Orlandi (UC Santa Cruz): "Bayesian Perception Is Ecological Perception" (KEYNOTE)

Derek H. Brown (Brandon University): “Colour Layering and Colour Relationalism” (Commentators: Mazviita Chirimuuta and Jonathan Cohen)

Jonathan Farrell (Manchester): “‘What It Is Like’ Talk Is Not Technical Talk” (Commentators: Robert Howell and Myrto Mylopoulos)

E.J. Green (Rutgers University): “Structure Constancy” (Commentators: John Hummel and Jake Quilty-Dunn)

Assaf Weksler (Open University of Israel and Ben Gurion University): “Retinal Images and Object Files: Towards Empirically Evaluating Philosophical Accounts of Visual Perspective” (Commentators: René Jagnow and Joulia Smortchkova)

"A" Is Red, "I" Is White, "X" Is Black -- Um, Why?

This is just the kind of dorky thing I think is cool. Check out this graph of the color associations for different letters for people with grapheme-color synesthesia.

[click on the picture for full size, if it's not showing properly]

This is from a sample of 6588 synesthetes in the US, reported in Witthoft, Winawer, and Eagleman 2015. Presumably, they're not talking to each other. But there's a pretty good agreement that "A" is red, "X" is black, and "Y" is yellow. But you knew that already, right?

Now some of these results seem partly explicable: "Y" is yellow, maybe, because of the word "yellow" starts with "Y". That might also work for "R" red, "B" blue, and "G" green. For "A" I think of the big red apple with the "A is for apple" posters that ubiquitously decorate kindergarten classrooms. But "O" is not particularly associated with orange in this chart, nor "W" with white. And why are "X" and "Z" black? Because we're tired because it's near the end of the alphabet and our eyelids are starting to droop doesn't seem like a good answer. (Does it?)

You might wonder whether it's only synesthetes who have this consensus of associations, and how stable such associations are over time or between countries.

You're in luck, then, because here's another cool chart, from Australia in 2005!

[again, click for clearer view]

The colored bars are synesthetic respondents and the hatched bars are non-synesthetic respondents. The patterns are similar between synesthetes and non-synesthetes, but maybe with the non-synesthetes tending toward stronger associations between the color and the initial letter of the color word. Furthermore, again "A" is red, "I" is white, and "X" and "Z" are black. US and Australian synesthetes seems to agree that "O" is white, but the Australian non-synesthetes like their "O" orange. For some reason, "D" is now brown (47%!).

There are some older US data from the underappreciated early introspective psychologist Mary Whiton Calkins in her classic 1893 paper on synesthesia. [Pop quiz: Who are the only three people to have been president of both the American Psychological Association and the American Philosophical Association? Answer: William James, John Dewey, and Mary Whiton Calkins.] She reports that synesthetes tend to associate "I" with black and "O" with white. "O" being white matches the synesthete reports from the US and Australia in 2015 and 2005, but Calkins's black "I" is different. Calkins reports this possible explanation for the whiteness of "O", from one of her participants, seeming to find it plausible: O "= cipher = blank = sheet of white paper".

Witthoft et al. 2015 found that almost a sixth of their participants born in the US in the late 1970s (but not those born before 1967) seem to have letter-color associations that match much better than chance with the colors of the letters of this then-popular magnet toy:

[image source]

Neat finding. Of course, the darned toy has "X" purple and "Z" orange, so it's all wrong!

Brang, Rouw, Ramachandran and Coulson 2011 find a weak tendency for similarly-shaped letters to associate to similar colors in US sample. Irish-based Barnett et al. 2008 and British-based Simner et al. 2015 find broadly similar patterns to the other recent English-language populations.

Spector and Maurer 2011 find that even pre-literate English-speaking Canadian toddlers associate "O" and "I" with white and "X" and "Z" with black, though they do not share older participants' associations of "A" with red, "B" with blue, "G" with green, and "Y" with yellow. They hypothesize that jagged shapes ("X" and "Z") might be more likely to have shaded portions in a natural environment than non-jagged shapes ("O" and "I"), and that other, later associations might be language based. However, color maps of Swiss research on German-language synesthetes (Beeli, Esslen, and Jaencke 2007) shows no such relationship (see the chart on p. 790) -- for example with more participants associating "X" with white or light gray than with black or dark gray (though Simner et al. have a German subset which do show black associations with "X" and "Z"). Beeli et al. find a weak tendency for higher frequency letters to be associated with higher saturation colors in a German-language sample. Rouw et al. 2014 found that Dutch and English-speaking non-synesthetic participants had similar associations for "A" (red), "B" (blue), "D" (brown), "E" (yellow), "I" (white), and "N" (brown). Hindi participants, with their different alphabet, had a rather different set of associations -- though the first letter of the Hindi alphabet was also associated with red. They speculate that the first letter in each alphabet gets a "signal" color.

Okay, so now you know!

Let me leave you then, with this highly unnatural thought:

Whoa.

Introspecting My Visual Experience "as of" Seeing a Hat?

In "The Unreliability of Naive Introspection" (here and here), I argue, contra a philosophical tradition going back at least to Descartes, that we have much better knowledge of middle-sized objects in the world around us than we do of our stream of sensory experience while perceiving those objects.

As I write near the end of that paper:

The tomato is stable. My visual experience as I look at the tomato shifts with each saccade, each blink, each observation of a blemish, each alteration of attention, with the adaptation of my eyes to lighting and color. My thoughts, my images, my itches, my pains – all bound away as I think about them, or remain only as interrupted, theatrical versions of themselves. Nor can I hold them still even as artificial specimens – as I reflect on one aspect of the experience, it alters and grows, or it crumbles. The unattended aspects undergo their own changes too. If outward things were so evasive, they’d also mystify and mislead.

Last Saturday, I defended this view for three hours before commentator Carlotta Pavese and a number of other New York philosophers (including Ned Block, Paul Boghossian, David Chalmers, Paul Horwich, Chris Peacocke, Jim Pryor).

One question -- raised first, I think, by Paul B. then later by Jim -- was this: Don't I know that I'm having a visual experience as of seeing a hat at least as well as I know that there is in fact a real hat in front of me? I could be wrong about the hat without being wrong about the visual experience as of seeing a hat, but to be wrong about having a visual experience as of seeing a hat, well, maybe it's not impossible but at least it's a weird, unusual case.

I was a bit rustier in answering this question than I would have been in 2009 -- partly, I suspect, because I never articulated in writing my standard response to that concern. So let me do so now.

First, we need to know what kind of mental state this is about which I supposedly have excellent knowledge. Here's one possibility: To have "a visual experience as of seeing a hat" is to have a visual experience of the type that is normally caused by seeing hats. In other words, when I judge that I'm having this experience, I'm making a causal generalization about the normal origins of experiences of the present type. But it seems doubtful that I know better what types of visual experiences normally arise in the course of seeing hats than I know that there is a hat in front of me. In any case, such causal generalizations are not sort of thing defenders of introspection usually have in mind.

Here's another interpretative possibility: In judging that I am having a visual experience as of seeing a hat, I am reporting an inclination to reach a certain judgment. I am reporting an inclination to judge that there is a hat in front of me, and I am reporting that that inclination is somehow caused by or grounded in my current visual experience. On this reading of the claim, what I am accurate about is that I have a certain attitude -- an inclination to judge. But attitudes are not conscious experiences. Inclinations to judge are one thing; visual experiences another. I might be very accurate in my judgment that I am inclined to reach a certain judgment about the world (and on such-and-such grounds), but that's not knowledge of my stream of sensory experience.

(In a couple of other essays, I discuss self-knowledge of attitudes. I argue that our self-knowledge of our judgments is pretty good when the matter is of little importance to our self-conception and when the tendency to verbally espouse the content of the judgment is central to the dispositional syndrome constitutive of reaching that judgment. Excellent knowledge of such partially self-fulfilling attitudes is quite a different matter from excellent knowledge of the stream of experience.)

So how about this interpretative possibility? To say I know that I am having a visual experience as of seeing a hat is to say that I am having a visual experience with such-and-such specific phenomenal features, e.g., this-shade-here, this-shape-here, this-piece-of-representational-content-there, and maybe this-holistic-character. If we're careful to read such judgments purely as judgments about features of my current stream of visual experience, I see no reason to think we would be highly trustworthy in them. Such structural features of the stream of experience are exactly the kinds of things about which I've argued we are apt to err: what it's like to see a tilted coin at an oblique angle, how fast color and shape experience get hazy toward the periphery, how stable or shifty the phenomenology of shape and color is, how richly penetrated visual experience is with cognitive content. These are topics of confusion and dispute in philosophy and consciousness studies, not matters we introspect with near infallibility.

Part of the issue here, I think, is that certain mental states have both a phenomenal face and a functional face. When I judge that I see something or that I'm hungry or that I want something, I am typically reaching a judgment that is in part about my stream of conscious experience and in part about my physiology, dispositions, and causal position in the world. If we think carefully about even medium-sized features of the phenomenological face of such hybrid mental states -- about what, exactly, it's like to experience hunger (how far does it spread in subjective bodily space, how much is it like a twisting or pressure or pain or...?) or about what, exactly, it's like to see a hat (how stable is that experience, how rich with detail, how do I experience the hat's non-canonical perspective...?), we quickly reach the limits of introspective reliability. My judgments about even medium-sized features of my visual experience are dubious. But I can easily answer a whole range of questions about comparably medium-sized features of the hat itself (its braiding, where the stitches are, its size and stability and solidity).

Update, November 25 [revised 5:24 pm]:

Paul Boghossian writes:

I haven't had a chance to think carefully about what you say, but I wanted to clarify the point I was making, which wasn't quite what you say on the blog, that it would be a weird, unusual case in which one misdescribes one's own perceptual states.

I was imagining that one was given the task of carefully describing the surface of a table and giving a very attentive description full of detail of the whorls here and the color there. One then discovers that all along one has just been a brain in a vat being fed experiences. At that point, it would be very natural to conclude that one had been merely describing the visual images that one had enjoyed as opposed to any table. Since one can so easily retreat from saying that one had been describing a table to saying that one had been describing one's mental image of a table, it's hard to see how one could be much better at the former than at the latter.

Roger White then made the same point without using the brain in a vat scenario.

I do feel some sympathy for the thought that you get something right in such a case -- but what exactly you get right, and how dependably... well, that's the tricky issue!

Synchronized Movement and the Self-Other Boundary

I'm traveling around Britain. (Oxford, Bristol, Birmingham, Edinburgh, and St Andrews so far, Sheffield and Bristol again tomorrow and the day after.) I have some post ideas, but I'm too worn out to trust my judgment that I'll do them right, so I'm going to exert the long-time blogger's privilege of reposting something from ancient days -- 2007! Jonathan Haidt and the rubber hand illusion aren't as cutting-edge in 2013 as they were in 2007, but still....

.......................................

I've been reading The Happiness Hypothesis, by Jonathan Haidt -- one of those delightful books pitched to the non-specialist, yet accurate and meaty enough to be of interest to the specialist -- and I was struck by Haidt's description of historian William McNeill's work on synchronized movement among soliders and dancers:

Words are inadequate to describe the emotion aroused by the prolonged movement in unison that [military] drilling involved. A sense of pervasive well-being is what I recall; more specifically, a strange sense of personal enlargement; a sort of swelling out, becoming bigger than life, thanks to participation in collective ritual (McNeill 1997, p. 2).

Who'd have thought endless marching on the parade-grounds could be so fulfilling?

I am reminded of work by V.S. Ramachandran on the ease with which experimenters can distort the perceived boundaries of a subject's body. For example:

Another striking instance of a 'displaced' body part can be demonstrated by using a dummy rubber hand. The dummy hand is placed in front of a vertical partition on a table. The subject places his hand behind the partition so he cannot see it. The experimenter now uses his left hand to stroke the dummy hand while at the same time using his right hand to stroke the subject's real hand (hidden from view) in perfect synchrony. The subject soon begins to experience the sensations as arising from the dummy hand (Blotvinick and Cohen 1998) (Ramachandran and Hirstein 1998, p. 1623).

Also:

The subject sits in a chair blindfolded, with an accomplice sitting in front of him, facing the same direction. The experimenter then stands near the subject, and with his left hand takes hold of the subject's left index finger and uses it to repeatedly and randomly to [sic] tap and stroke the nose of the accomplice while at the same time, using his right hand, he taps and strokes the subject's nose in precisely the same manner, and in perfect synchrony. After a few seconds of this procedure, the subject develops the uncanny illusion that his nose has either been dislocated or has been stretched out several feet forwards, demonstrating the striking plasticity or malleability of our body image (p. 1622).

So here's my thought: Maybe synchronized movement distorts body boundaries in a similar way: One feels the ground strike one's feet, repeatedly and in perfect synchrony with seeing other people's feet striking the ground. One does not see one's own feet. If Ramachandran's model applies, repeatedly receiving such feedback might bring one to (at least start to) see those other people's feet as one's own -- explaining, in turn, the phenomenology McNeill reports. Perhaps then it is no accident that armies and sports teams and dancing lovers practice moving in synchrony, causing a blurring of the experienced boundary between self and other?

SarahAbraham

Through a harmony of dendrites, Sarah came to feel touch upon Abraham’s skin. They were waltzing upon the beach, Ishbak on the immutable piano, and a frond brushed Abraham’s back. Sarah felt the frond as though on her own back. She caressed Abraham’s left shoulder and felt the caress as though upon her own shoulder. Abraham’s right hand was touching the skin under Sarah’s arm, and Sarah felt not only his fingers there in the usual way, but also a new complement: the smoothness of her ribs upon her own right hand. She had been feeling that smoothness for a while, she realized, intermingled with the more familiar touch of Abraham’s left hand upon her right as they danced.

They danced three songs in this manner, then lay together upon the sand. Sarah touched the back of her neck with a twig and saw Abraham scratch his own neck. They made love in a new way.

Sarah gazed upon Abraham as he observed the sky. She called to Ishbak and Midian. Sarah and Abraham lay face down upon blankets while the sons of Keturah touched their backs, and Sarah learned to distinguish Abraham’s sensations from her own. She now had two backs, two bodies.

Through a harmony of retinas, Sarah came to see through Abraham’s eyes. At first, it was a faint tint upon her field of view – her own form, maybe, bent toward the fire pit, as Abraham watched her from the side, her figure like a wraith upon the fire that she more vividly saw. The wraith was jumpy, unpredictable; she could not fully guess Abraham’s saccades as his eyes gathered the scene. Over days, the visions livened and settled. Sarah did not know if she merely learned better to anticipate Abraham’s eye movements or if she instead also gained partial control.

[for the second half of this story, email me at eschwitz at domain: ucr.edu]

Two Types of Hallucination

Oliver Sacks is one of the great essayists of our time. I have just finished his book Hallucinations.

Sacks does not, I think, adequately distinguish two types of hallucination. I will call them doxastic and phenomenal. In a phenomenal hallucination of A, one has sensory experience as of A. In a doxastic hallucination, one thinks one has sensory experience as of A. The two can come apart.

Consider this description, from page 99 of Hallucinations (and attributed to Daniel Breslaw via David Ebin's book The Drug Experience).

The heavens above me, a night sky spangled with eyes of flame, dissolve into the most overpowering array of colors I have ever seen or imagined; many of the colors are entirely new -- areas of the spectrum which I seem to have hitherto overlooked. The colors do not stand still, but move and flow in every direction; my field of vision is a mosaic of unbelievable complexity. To reproduce an instant of it would involve years of labor, that is, if one were able to reproduce colors of equivalent brilliance and intensity.

Here are two ways in which you might come to believe the above about your experience: (1.) You might actually have visual experiences of the sort described, including of colors entirely new and previously unimagined and of a complexity that would require years of labor to describe. Or (2.) you might shortcut all that and simply arrive straightaway at the belief that you are undergoing or have undergone such an experience -- perhaps with the aid of some unusual visual experiences, but not really of the novelty and complexity described. If the former, you have phenomenally hallucinated wholly novel colors. If the latter, you have merely doxastically hallucinated them.

The difference seems important -- crucial even, if we are going to understand the boundaries of experience as revealed by hallucination. And yet phenomenal vs. merely doxastic hallucinations might be hard to distinguish on the basis of verbal report alone, and almost by definition subjects will be apt to confuse the two. I can recall no point in the book where Sacks displays sensitivity to this issue.

Once I was attuned to it, the issue nagged at me again and again in reading:

Time was immensely distended. The elevator descended, "passing a floor every hundred years" (p. 100).

Then my whole life flashed in my mind from birth to the present, with every detail that ever happened, every feeling and thought, visual and emotional was there in an instant (p. 102).

I have had musical hallucinations (when taking chloral hydrate as a sleeping aid) which were continuations of dream music into the waking state -- once with a Mozart quintet. My normal musical memory and imagery is not that strong -- I am quite incapable of hearing every instrument in a quintet, let alone an orchestra -- so the experience of hearing the Mozart, hearing every instrument, was a startling (and beautiful) one (p. 213).

The possibility of merely doxastic hallucination might arise especially acutely when subjects report highly unusual, almost inconceivable, experiences or incredible detail beyond normal perception and imagery; but of course the possibility is present in more mundane hallucination reports too.

(A fan of Dennett might suggest that there's no difference between the phenomenal and doxastic hallucinations; but I don't know what Dennett himself would say -- probably something more complex than that.)

The Tyrant's Headache

When the doctors couldn’t cure the Tyrant’s headache, he called upon the philosophers. “Show me some necessary condition for having a headache, which I can defeat!”

The philosophers sent forth the great David K. Lewis in magician’s robes....

[See the remainder of this story here. Hint: It doesn't have a happy ending.]

New Essay: The Problem of Known Illusion and the Resemblance of Experience to Reality

I'll be presenting a new essay at the Philosophy of Science Association meeting in San Diego on Friday in the morning sessions. I've been drafting it out since 2010, in various shapes and lengths, and I presented it orally in 2011 at UMSL, but the thing always seems to crumble in my hands, and until now I haven't been comfortable posting a circulating draft. However, by stripping it down to 2000 words for a brief oral presentation, I can conveniently decline to delve into the issues that keep stymieing me and present the core idea fairly simply, I hope, with a couple of examples.

Abstract: If Locke is right, when I visually experience a cubical thing and judge rightly that it is in fact a cube, then there is a mind-independent thing out there the shape of which in some important way resembles my experience of its shape. If Kant is right, in contrast, we have no good reason to think that things in themselves are cubical; there's nothing independent of the human mind that has cubical properties that resemble the properties of my visual experience of cubes. I believe we can start to get a handle on this dispute empirically through introspection. Suppose that there are multiple different ways of veridically experiencing the same object and that it can sometimes be the case that there's no good reason to think that one of the two different experiences more closely resembles things as they are in themselves. It would then seem to follow that there's a kind of looseness between features of experience and features of things in themselves. Things in themselves might be more like this or they might be more like that or somewhere in between; but we can no longer say that we know they are like this -- a miniature Kantian victory over Locke. And then the question would be: How far can we push this type of argument? In this paper, I consider two test cases: convex passenger-side car mirrors and inverting lenses of the sort invented by George Stratton.

Full paper here. As always, comments and criticisms welcome, either on this post or by email.

Kant Meets Cyberpunk

In 1992, my first year of graduate school, I read William Gibson's cyberpunk classic Neuromancer and, by chance, Kant's Critique of Pure Reason at the same time. It seemed to me that the two were intimately connected, but various older grad students in my Kant class pooh-poohed my ideas about this and I lacked the intellectual confidence to pursue it farther.

But the thought has stayed with me. In Neuromancer, like in Tron, there's an artificial environment that one can travel in virtually. One "enters" it by jacking into a neural interface. Also like Tron, but unlike The Matrix, the artificial environment of Neuromancer substantially differs in its basic structural features from the real-world environment. Derived from early computer graphics programs, Neuromancer's cyberspace matrix is composed of lines of light arranged into geometrical figures in simple colors; space is experienced in discrete units and movement is in rectangular clicks. As I seem to remember having imagined it, and as we might as well imagine it for present purposes (though now looking through the text, this not accurate), everything is laid out rectilinearly and the only colors are simple primaries.

So now imagine that you were born jacked into such a matrix. You might think that objects were necessarily laid out in straight lines at right angles and possessed of only primary colors, and that space came in discrete units. But this would be a feature, not of things as they are "in themselves", but rather of how your mind processes the structured input it is given. We might even imagine (and maybe it's true) that a human mind that developed in such a matrix couldn't even conceive of curves, oblique angles, tertiary colors, or continuous space. For such a mind, objects as presented in the cyberspace matrix would be the only empirically available reality, and what we non-cyberspace-embedded folks consider to be the real world would be an incomprehensible "noumenal realm" behind those appearances. Conversely, we might imagine -- though it's impossible to depict vividly in a novel -- this matrix-grown strange baby to have new sensory modalities and new basic ways of cognizing the world that are unfamiliar to us, especially if its brain is artificially enhanced (a fourth "spatial" dimension for matrix-informational layout would be a conservative start).

The analogy to Kant is imperfect. Kantian purists will, I suppose, cringe at the comparison. Time, causation, three-dimensionality, and many other properties are shared by the Neuromancer matrix and the reality outside of the matrix. And the features of the matrix available to the embedded mind might not be given "a priori" in a strict Kantian sense (whatever Kant's sense is). I'm sure there are other important disanalogies too. But as a way of getting a toehold on the Kantian picture, I still rather like the comparison. We are born into naturally given matrixes that necessarily structure our experiential encounter with the world, and out of which we cannot break, even in imagination. All this that I see and hear is just user interface.

Such thoughts are doubly apt, perhaps, if we are actually already living in a giant computer simulation.

Strange Baby

Suppose that a baby is born at the Institute for Evil Neuroscience. Well, maybe not a baby exactly -- a human baby brain, suspended in nutritive fluid, with a truncated respiratory, digestive, and circulatory system hooked up to an oxygen input tube and a feeder tube, with connections to the brain's punishment and reward center so that the right kinds of nutritive/homeostatic inputs trigger reward, while deprivation and drift from homeostasis trigger punishment. Additionally, this baby brain is supplemented with two novel appendages of neural tissue. It has one general-purpose appendage, with ten times as many neurons and neural connections as an ordinary human brain, divided into subareas of various sizes and various levels of connectivity to each other, and constituted by a variety of neurons in a variety of ratios, but with no pre-dedicated purpose of any sort. And it has one brain-sized direct interface with an ordinary desktop computer with a variety of software and with internet server functionality. These neural appendages are connected to, or grow out of, the corpus callosum, almost like cortical hemispheres. More or less, this is a four-hemisphered baby.

The first thing Strange Baby has to learn is to feed itself. It has a bank account of $10 million to start with. Scientists at the IEN nudge some of Strange Baby's early processing toward ordering nutrient packs from hospital supply centers, which at first they hook up to its feeder tube. Soon, they start to wean it from dependence on them by teaching it to pay independent home caretakers to do that work: the IEN scientists stimulate its reward centers when it does the kinds of things that give it increasing independence of them. At first they do so by explicitly giving fairly directive input, then they slowly reduce the structure of the input, letting Strange Baby's own reward center take over. Eventually, through their guidance, Strange Baby is paying not only for home caretakers but also for a custodian, for occasional building repairs, for power and air-conditioning, etc., as well as for direct maintenance on its computer (which it starts to expand and upgrade). Once the IEN scientists are confident Strange Baby can maintain homeostasis, they no longer regularly enter the building. At first, they visit occasionally to give Strange Baby medical checkups, but soon these too are contracted out.

Strange Baby's $10 million won't last forever, so she needs to learn to supplement her bank account. She has picked up linguistic patterns from internet usage, gaining differential reinforcement from chat groups: The IEN scientists set things up so that if Strange Baby can produce text strings that generate extended and diverse responses, she finds that rewarding. The IEN scientists had also kindly given Strange Baby an initial nudge toward Mturk, and gave it some initial input-output templates for starting Mturk accounts and accepting Mturk tasks. Through trial and error, Strange Baby found patterns among Mturk tasks that yielded bank account increases, generating neural reward.

Eventually, Strange Baby is a fully linguistic member of the internet community, motivated to maintain homeostasis, increase her bank account, and say things in chat rooms, blogs, and on other social networking sites that generate long and diverse responses.

Strange Baby can't see with her eyes, for she has no human eyes, though she can access public cameras and she can request camera input from friends. Nor can Strange Baby hear in the normal way, though she can access microphones and she can receive voice-protocol inputs and produce voice-protocol outputs. Eventually, Strange Baby convinces a friend to put a camera, microphone, speaker, and monitor display in her brain room so that she can directly observe her caretakers and contractors and communicate with them in modes they're comfortable with. She chooses a human face avatar that expresses her personality and self-image.

Strange Baby's sensory and cognitive experiences will share some features with our own, but she will also be very different. Her visual and auditory experience will, presumably, be multi-perspectival. She will be directly sensitive to internet slowdowns. And she will be sensitive either to input from her neural integrated silicon computer or to internet input (which of these will seem to her to be the sensory surface?) -- directly sensitive, no visual user interface required -- perhaps with special feelings associated with the balance of her bank accounts and the length and diversity of her various internet discussions. The computer/internet will, presumably, be by far her most important stream of sensory input. (We can call it "sensory", can't we?)

Strange Baby will have twelve times the neural capacity of an ordinary human being, with her dedicated computer/internet double-hemisphere, and with her trillion-neuron flexible reservoir which presumably gets shaped in ways useful to her goals. It seems reasonable to suppose that she will have conscious experiences of various sorts associated with these brain areas and brain functions. Such experiences will probably seem alien to us, like color to a blind person. Nor will the part of her brain that would be visual cortex in a normal human being necessarily be dedicated to visual processing, or auditory cortex to auditory processing.

Strange Baby will no doubt find even very complicated arithmetic easy; and presumably she will have a major advantage over the rest of us in more complex sorts of formal reasoning as well, since she will combine something like human neural capacities with computer capacities and with her own unique areas of neural tissue. I wonder, though: If she uses the computer's processors for arithmetic, will it seem to her that she is checking the computer like we do, but more directly and non-visually, or will it seem like the computer is part of her so that checking it is like using her own memory or reasoning? If the latter, Strange Baby might find even the most advanced human logicians and mathematicians painfully daft. Who knows in what other areas she might choose to excel, but it seems likely she could do very well in many areas, perhaps finding it easy to learn many different facts and intellectual skills.

She will want children.

"Objects in Mirror Are Closer Than They Appear"

... so it says, at least, on my passenger side mirror.


(image from http://amchurchadultdiscipleship.net)

I've been worrying though, are they closer than they appear?  This might seem a strange thing to worry about, but I refuse to be thus consoled.

Here's a case for saying that objects in the mirror are closer than they appear: The mirror is slightly convex so as to give the driver a wider field of view.  As a result, the expanse of mirror reflecting light from the object into my eye is smaller than the expanse would be if the mirror were flat.  Thus, the size of the object "in the mirror" is smaller than it would be in a flat mirror.  If we assume that flat mirrors accurately convey size, it seems to follow that the size of the object in the mirror is inaccurately small.  Finally, apparent distance in a mirror is determined by apparent size in a mirror, smaller being farther away.

The argument for the other side is, at first blush, much simpler: Objects in the mirror are no closer than they appear, at least for me, because as an experienced driver I never misjudge, or am even tempted to misjudge, their distance.

Now both of these arguments are gappy and problematic.  For example, on the first argument: Why should flat mirrors be normative of apparent size?  And why shouldn't we say that the object is larger than it appears (but appearing the right distance away), rather than closer than it appears (but perhaps appearing the right size)? That is, why does it look like a distant, full-sized car rather than a nearby, smallish car?

You might be tempted to mount a simpler argument for the "closer than they appear" claim: A naive mirror-user will misjudge the distance of objects seen in a slightly convex mirror.  The naive mirror-user's misjudgments are diagnostic of apparent size -- perhaps they are based primarily on "appearances"? -- and this apparent size does not change with experience.  The experienced mirror-user, in contrast, makes no mistakes because she learns to compensate for apparent size.  But this argument is based on the dubious claim that the experience of a novice perceiver is qualitatively the same as the experience of an expert perceiver -- a claim almost universally rejected by contemporary philosophers and psychologists.  It's also unclear whether the naive mirror-viewer would make the mistake if warned that the mirror is convex.  (Can apparent size in a mirror be contingent upon verbally acquired knowledge of whether the mirror is slightly convex or concave?)

Should we, then, repudiate the manufacturers' claim, at least as it applies to experienced drivers?  Should we, perhaps, recommend that General Motors hire some better phenomenologists?  Well, maybe.  But consider carnival mirrors: My image in a carnival mirror looks stretched out, or compressed, or whatever, even if I am not for a moment deceived.  Likewise, the lines in the Poggendorff Illusion look misaligned, even if I have seen the illusion a thousand times and know exactly what is going on.  Things look rippled through a warped window, no matter how often I look through that window.  Perhaps you, too, want to say such things about your experience.  If so, how is the passenger-side mirror case different?

Here is one way it might be different: It takes a certain amount of intellectual stepping back to not be taken in by the carnival mirror or the Poggendorff Illusion or the warped window.  The visual system, considered as a subset of my whole cognitive system, is still fooled.  And maybe this isn't so for the passenger-side mirror case.  But why not?  And does it really take such intellectual stepping back not to be fooled in the other cases?  Perhaps there's a glass of water on my table and the table looks warped through it.  I'm not paying any particular attention to it.  Is my visual system taken in?  Am I stepping back from that experience somehow?  It's not like I just ignore visual input from that area: If the table were to turn bright green in that spot or wiggle strangely, I would presumably notice.  Is my father's visual system fooled by the discontinuity between the two parts of his bifocals?  Is mine fooled by the discontinuities at the edge of my rather strong monofocals as they perch at the end of my nose?  And what if, as Dan Dennett and Mel Goodale others have suggested, there are multiple and possibly conflicting outputs from the visual system, some fooled and some not?

Can we say both that objects are farther than they appear in passenger-side mirror (in one sense) and that they aren't (in some other sense)?  I'm inclined to think that such a "dual aspect" view in this case only doubles our problems, for it's not at all clear what these two senses would be: They can't be the same two senses, it seems, in which a tilted penny is sometimes said to look in one way round and in another way elliptical -- for what would we then say about the tilted penny viewed in a convex mirror?  We would seem to need three answers.

Hey, wait, don't drive off now -- we've only started!

The Spelunker Illusion

Ten years ago, when I visited the Luray Caverns in Virginia, the tour guide took us down to the deepest cave and turned off the lights. He told us to wave our hands in front of our faces and asked if we could see our hands waving. We could, faintly -- or so we thought. He then asked us to wave our hands in front of our friends' faces. Our friends' hands we couldn't see at all. When we thought we could see our own hands we were fooling ourselves, he said. Not a single photon penetrated that darkness; no light actually came from our hands into our eyes.

Call this the spelunker illusion. The existence of this illusion appears to be common lore among avid cave explorers. I have also confirmed it in more pedestrian lightless environments. Yet no psychologist discusses it in any of literature I've reviewed in writing my forthcoming chapter on visual experience in darkness. But surely someone must have written a treatment? If you know of any discussions, I'd appreciate the reference!

I see three possible explanations of the spelunker illusion:

(1.) The brain's motor output creates hints of visual experience in accord with that output.

(2.) Since you know you are moving your hand, your visual system interprets low-level sensory noise in conformity with your knowledge (much as you might see a meaningful shape in a random splash of line segments).

(3.) There is no visual experience of motion, but the spelunker mistakenly thinks there is such experience because she expects there to be.

There might be other explanations too. I can see how we might start to empirically tease apart the three explanations above. For example, (1) and (2) seem to come apart if you have your friend move your passive hand rather than actively moving your hand yourself. And (3) can come apart from (1) and (2) if we can quash the expectation of experience.

Is this a mere curious triviality? Maybe. But the three explanations above do bear somewhat differently on different theories of sensory experience and our knowledge of it. Like other illusions, this illusion promises to reveal something about the hidden operation of the visual system, if it can be properly understood.

Update, April 28, 2014:

Leonard Rosgole and Miguel Roig point out to me that these phenomena were reported in the psychological literature in Hofstetter 1970, Brosgole and Neylon 1973, Brosgole and Roig 1983. They have since been confirmed by Dieter et al. 2013. If you're aware of earlier sources, I'd be curious to know.

Qualia Inversion: Sound and Color (A Contest with a "Valuable Prize"!)

If you're the kind of person who reads philosophy blogs, you've probably heard of inverted qualia thought experiments. The most famous example is red-green inversion: The red-green invert is someone who has reddish color experiences when she looks at green things (grass, leaves) and has greenish color experience when she looks at red things (blood, ripe tomatoes). Since the invert, like the rest of us, learns the meaning of color terms by example, her language and behavior is entirely, or at least virtually, indistinguishable from anyone else's. She uses the English word "red" to refer to the color of blood and "green" to refer to the color of grass, despite the difference in her color experiences of those things.

In a talk at UC Riverside a couple of weeks ago, Saul Kripke asserted that no philosopher had ever suggested the possibility of sound-color qualia inversion -- that is, the possibility of a person who experiences sound qualia when stimulated by light and color qualia when stimulated by sonic vibrations. Let's be clear that Kripke was not denying the possibility of synaesthesia. He was not denying that people sometimes (for example) experience colors alongside sounds when stimulated by sounds. Kripke's claim, rather, was that no philosopher had contemplated a true sound-color qualia invert -- someone who normally experiences sound rather than color when stimulated by light and color rather than sound when stimulated by sonic vibration and whose language and behavior from the outside is indistinguishable from that of non-inverts.

Kripke said this twice. I told him I was pretty sure he was wrong and that I had read such a discussion. Kripke challenged me to send him the citation. After a little research, I turned up my source: an unpublished essay by one of my graduate students, Nathan Westbrook. When I asked Nathan whether he knew of any precedents, he said he didn't. I also tried asking someone who had recently published a review of the qualia inversion literature; he too said he didn't know of anyone who had advanced that type of example.

But given the huge number of philosophy articles published each year and the prominence of qualia inversion examples, I feel sure someone must have discussed this kind of case somewhere. Therefore, I offer a challenge: Find a published discussion of sound-color qualia inversion. The winner will receive a "valuable prize" -- hm, what can I offer? How about: a drink of your choice (coffee, beer, whatever) on me, next time we are in the same city. (Okay, maybe that's no so valuable.)

Rules:

* The contest is open until June 14th or until someone delivers a satisfactory example, whichever comes later.

* To be satisfactory, the discussion must be published in a reputable philosophy journal or press.

* To be satisfactory, the discussion need not ultimately endorse the possibility of color-sound qualia inversion, just take it seriously.

* If more than one satisfactory example is submitted, the person who submits the best example will be declared the winner, where I will judge "best" impressionistically, criteria including but not limited to: the length and quality of the discussion, the prominence of the writer or venue, and how seriously the possibility is taken.

* If more than one person submits the best example, the first person to submit the best example will be declared the winner.

* Submit your example as a comment on this post or by email to me.

For the record, I lean toward thinking that sound-color qualia inversion is possible in a conceptual/metaphysical/pulling-it-out-of-my-a-priori-hindquarters-for-the-little-that's-worth sense of possibility.

Color experiences famously differ along three dimensions: hue, saturation, and lightness or brightness. They also differ in egocentric, subjective location. To work an inversion with sound, we need a one-to-one mapping of dimensions of variation. Subjective location would appear to be easy, since both colors and sounds have subjective location. Since brightness and saturation are both unidimensional, we might be able to map them one-to-one onto pitch and volume, which are also unidimensional. Hue varies in a bit more complex a way, with red-green as opposites and blue-yellow as opposites, but perhaps patterns in the overtone series could be used. Probably the hue-overtone series mapping would require some tweaking to work, but presumably human-like beings with a slightly different set of visual and auditory capacities could exhibit a clean mapping (e.g., if the beings were only capable of discriminating certain patterns in overtone variation). Another complication is our much higher sensitivity to variation in visual as opposed to auditory position. But I don't see why, for the purposes of the thought experiment, we shouldn't be liberal about such matters: The sound-color invert, for example, might be an invert only of a relatively poor-sighted person and/or might have an exquisite appreciation of subtle variations in the position of sound sources subjective location of sound qualia.

How Far Away Is the Television Screen of Visual Experience?

... not that I think there really is one, even in a loose, metaphorical sense. (See here.) But:

David Boonin (a visiting speaker from Colorado) and UCR graduate students Alan Moore and Matt Braich and I were hiking up Mt. Rubidoux. From the top, we could see several miles across town to the UCR campus. We pointed out to Boonin the clock tower, and then Alan said that the humanities building housing the philosophy department was also visible nearby, down and to the right, "about an inch and a half away".

What, an inch and a half away?! Alan's statement -- as I'm sure he knew -- sharply conflicted with my published views about the nature of the visual experience of perspective. And yet I knew exactly what Alan meant. He had effectively pointed out the spot. It seemed to me that "an inch and a half" was a much better description of the apparent distance than, say, a millimeter or twenty feet. (Of course the real distance is much larger than any of those.)

My thumb is about 3/4 of an inch wide. Holding it at arm's length, I saw that it almost perfectly occluded the distance between the clock tower and the humanities building. Thus, if the television screen of visual experience were arm's length away, Alan should have said that the distance was 3/4 of an inch. From the fact that the building's apparent distance (in some sense of "apparent distance"!) was an inch and a half, I thus geometrically derive the conclusion that the television screen of visual experience is about five feet away.

There, proved!

Curveball Illusion

I hadn't seen this curveball illusion before. Very striking and surprising. I haven't had a chance to look into the theory behind it yet, but it seems to me to suggest something strange about the mapping of visual input into peripheral space.

(Thanks to Paul Hoffman for the pointer.)

What Is It Like to Feel Sleepy?

Here are three types of conscious experience, or "phenomenology", that it's difficult to deny:

(1.) sensory experience (like the experience of redness produced by looking at a red object, like the taste of saltiness in one's mouth),
(2.) imagery experience (like a picture in one's mind's eye of the Taj Mahal, or a tune or sentence running silently through one's head), and
(3.) emotional experience (the rush of anger, the shock of sudden fear).

Some scholars think one or more of these reduces to or is a variant of another (maybe emotional experience is just sensory experience of the body [as William James says], maybe imagery experience is just a faint version of sensory experience [as David Hume says]). But clearly we have all three types of experience.

It's sometimes argued that we also have other types of experience, but there has never been a consensus on what the other types are. Imageless thought or "cognitive phenomenology" is one suggestion, which has been getting a lot of attention recently (e.g., by Charles Siewert, David Pitt, and Russ Hurlburt) -- the supposed experience we have of thinking something which is not just a matter of having images or emotional experiences of a certain sort, but which has its own irreducible phenomenology. Early in the 20th century, E.B. Titchener argued against the existence of such cognitive phenomenology, suggesting that it mostly reduces to visual images, inner speech (both forms of imagery), and the like. More recently, William Robinson and Jesse Prinz have argued similarly against it.

How about the experience of feeling sleepy? I can't recall any good discussions of this in the philosophical or psychological literature. (If I've missed something, please let me know!) Is that reducible to one or more of those three types of experience?

Maybe it's a type of sensory experience? To think clearly about this, we need first to think about what other kinds of experiences are sensory -- for the categories above are clearly incomplete unless we have a fairly broad notion of "sensory", such that pains count as sensory experiences and feelings of muscular tension and limb position and feelings of fullness or discomfort in the alimentary canal. Is feeling sleepy sensory in the same way these other experiences are -- a matter of experiencing how things are going in your body?

As it happens, I'm sleepy right now. (Hence the inspiration for this post.) This slight headache, this feeling that I'm tempted to describe as a heaviness near my eyes -- those seem like sensory experiences. But there's more to sleepiness than that. A lassitude in my limbs? Is that sensory? But could I have this very same heaviness and lassitude and not feel sleepy? Or feel sleepy without this heaviness and lassitude? My guess is -- but it's only a guess -- that there's something more.

Also: Sleepiness is as much a state one one's brain as of one's body. I can understand how detecting the condition of one's body is, in an appropriately broad sense, sensory; but is detecting the condition of one's brain also sensory? That doesn't seem right. The brain does all kinds of self-monitoring and engages in all kinds of feedback loops; would those, too, be "sensory"?

So maybe sleepiness is, experientially, an emotion? It has a valence, like emotion (negative, usually), and perhaps a typical facial posture. But it doesn't appear on most psychologists' lists of emotional states (sadness, happiness, fear, anger, surprise...). It doesn't seem to arise, usually, as a reaction to how things are going for you and those you care about, for example in response to a change for better or worse in one's condition, as emotions typically do. But maybe not all emotions are like that? (Is surprise even like that?) What is an emotion, exactly? Well, we won't solve that question today.

Or is the experience of sleepiness sui generis, just its own unique sort of thing? And if so, then the feeling of being well-rested, too? And who knows what all else? Feeling energetic? Competent? Lusty? Healthy? The boxes in which we're supposed to fit things, the categories of experience -- their borders seem no longer clear, or they won't stand still....