Showing posts with label deja trompé. Show all posts
Showing posts with label deja trompé. Show all posts

Thursday, July 22, 2021

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When I started grad school, one of the first things I did was to adopt a kitten that had been born earlier that summer in the apartment across the hall. Now, 18 years (!?!) later, here is a Eulogy for my Cat, in the form of a couple of cat-related anecdotes from my studies.

In my first year of school I was getting into the science of spatial vision - acuity, contrast, retina, V1, etc. I learned that a cat's visual acuity is like 5x worse than a human's. So, naturally, I figured that everything must look *blurry* to a cat.

See, I lived with this creature, and I would often think, how do things appear to her? I remember walking home late one night thinking about how stars appear to me as points - must they appear to a cat as blurry spots? And I realized that this couldn't be the case.

When I take off my glasses and see a point of light, it looks blurry in that I can see that what should be a point is actually smudged across a region of the visual field. And to see that smudge as a smudge, I must be seeing details within the region it fills.

If something appears as a point, that means that it has no apparent interior. So in fact, the acuity limit is telling us about the spatial resolution of appearance. Some visible thing that's smaller than the acuity limit must appear as a point. 

Without glasses, a point is imaged on my retina in a smudge that's a good fraction of a degree across. But my true visual acuity is in the range of 2 minutes of arc; so I see that smudge as an extended, 2d thing. My cat wouldn't see the smudge - she'd just see a point.

Now, years later I'm still making use of that insight, for example when I have argued that peripheral vision can and should look just as sharp as foveal vision - it's for the same reasons that a star should look like a point to my cat.

Another one, now about my perspective rather than the cat's. Some version of this is familiar to any of us: you see a dark shadow at night - is it the cat? or is it something else? There was one instance of this that I puzzled over for years.

I had a pair of shoes that I would sometimes leave by the wall in the hallway of my apartment in Boston - now we're in my first postdoc, 10 years ago. Time and again, I would see those shoes out of the corner of my eye and think, "Cat!" - then foveate and see, "shoes!'.

What fascinated me was that after the first time, I knew what was going on. That is, the high-level visual part of me knew they were shoes. But over and over, my early visual system was fooled - that brown shape of a certain size, on the floor, was most likely "Cat".

I started to collect these cases, where peripherally-seen X makes me think I'm seeing Y, even once I know X is really X. I posted an good case here a while back: (https://twitter.com/AndrewHaun3/status/1261891022625398784). But the prototype will always be Shoes->Cat.

Anyways, before I was so theoretically rigid as I am today, I used to wonder: when I thought the shoes were my Cat, did they actually *appear* as a Cat would appear? Did my mistaken recognition subtly reshape the spatial patterns so as to make them a better fit for "Cat"?

It does seem like this sort of thing can happen to some degree, e.g. with Ryota Kanai's "healing grid" illusion. But wholesale, at the object level? How could we find out? It doesn't matter, because I don't think that's what's happening here.

What I think is happening here, rather, is that I am experiencing a spatial form that is shoes-shaped, shoes-textured, etc. And it's decidedly not cat-shaped, cat-textured, etc - it's not clear cut pareidolia, as where I might see the Cat-shapedness of a Cat-shaped cloud. 

With the shoes, they're the right size and location for a Cat, and my super-sensitive Cat-recognizers are activated, and I experience recognition-of-Cat at the same time I experience a shoes-shaped, shoes-textured spatial gestalt. It's not a wholly congruent experience.

Even now, this week, when my Cat is no more, I've already made the mistake of thinking that a shadow in the hall was "Cat"; that a light *thump* in the other room was "Cat". Now, not only is it a mistake, it's an impossible mistake. But the brain does what it does.

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Tuesday, December 17, 2013

meaning and filling-in

Something I've been meaning to write about for a couple of weeks now: object meaning as filling-in, and how this idea is the explanation for cases of deja trompe.

We return to the idea that the visual field is a stack of properties that develop from one another along a relatively rigid hierarchy. So, a certain configuration of brightnesses, which can be seen as such (as brightnesses, or darknesses, or colors), can also be seen as an edge or some other broadband feature. In fact, given certain configurations of colors, given broadband percepts are compulsory and there is no choice but to see them. However, they do not exclude the more local aspects that seem to compose the features. From edges we go to surfaces and depths, and from there to objects and meanings and utilities.

All these levels of the visual hierarchy are experienced simultaneously and constitute conscious qualia - we are experientially aware of points of color or brightness, and we are aware of edges and lines independent of the surfaces they bound, and we are aware of surfaces independent of the objects the bound, and we are aware of objects (in the sense of depthful 'thingness') independent of the meanings they bound (what they "are"). But the independence of these qualia exists only in their separability, because in normal experience they are not causally independent - when a given configuration exists, the other levels are evoked compulsorily, and so qualia are correlated between levels.

Illusion often consists of violations of these correlations. So, we will see illusory contours where there are no variations in color or brightness to constitute them. Deja trompe, as I have described it, is seeing an object as something other than what it "is", and doing so repeatedly, involuntarily, and being aware of this repeated mistake (this is the literal meaning of the term). In the case of illusory contours, the normal correlation or association between patterns of color and edges can make one feel that something at that level is seen, i.e. that there are color or brightness qualia there, though I don't see them (what I see is an edge without any color variation). On the other hand, we certainly see the colors in the watercolor illusion, or in other filling-in effects, so it seems that it does happen that we can be tricked into generating qualia without the normal hierarchical causes, both up and down (and within) the hierarchy.

In seeing an object for something that it is not, what is happening? When I walk through the hallway to the kitchen, and see my cat sitting on the floor in one of her usual spots, looking up at me as I pass, only to realize in a fraction of a second that no, that's not my cat, those are my boots - what am I actually seeing, during the duration of the mistake? I see something there, a thing with similar color and size and shape as a cat or a pair of boots, and in a suitable location for either. So, am I seeing a cat, and then seeing a pair of boots? Or am I seeing a pair of boots, and thinking it's a cat, and then thinking it's a pair of boots? Or am I seeing something indeterminate and relatively formless, that can be either thing (deja trompe is really a creature of peripheral vision, so crowding is of course a thing)? What is seeing? What is thinking it is?

Obviously, I have an opinion. And, being a kind of expert in this sort of thing, it's an informed opinion. I think that seeing boots for cat, my low-level qualia are entirely boots-driven, so in that sense, I am seeing boots. If you put the boots and the cat side by side at the same location in the visual field, I am confident that I could discriminate them, though there's a test there. Actually, that's a nice idea: take the objects that are confused in a deja trompe, and measure their actual discriminability. So it could be that they are relatively indiscriminable, and what is seen is relatively indeterminate and formless.

Actually, whether the low-level qualia are distinctly bootslike or indeterminate doesn't matter much to my interpretation, just shifts things around a little. What is certainly not happening is that the low level qualia are going from being more catlike to more bootslike, or that they are changing at all. That is the striking thing here: that the low-level qualia do not change, although they seem to change, in what is either a metacognitive or memorial judgment. What is changing is the meaning of what is seen, and that is what is so interesting here. Because the low-level qualia are not sufficiently specifying the identity of the object, it is briefly mis-specified, something which almost never happens in normal visual experience. Once you know what something is, you virtually never mistake it for something else, except in cases where you do, and when that happens you note it or mention it to whoever else is in the room, because it's so surprising.

When it happens, deja trompe gives a strong impression that what is seen is changing from one thing to another. However, it only makes sense that this is happening at the highest levels. The lower-level qualia, I will maintain (when given the chance) are more determined by the sensory input, and the later qualia are determined by the lower-level qualia (and certainly also by other mechanisms that do not present themselves in consciousness). So, through this chain, errors or lack of specificity can build up, and you wind up with a mistake, at the top.

What it comes down to is that meaning, i.e. what a thing is, is a sort of filling-in, where in exactly the same way as the watercolor effect, but much more solidly and more vigorously, the multi-level boundaries of an object prompt it to be visually filled with meaning. I mean this literally, and I think it is obviously true: when you see a scene filled with objects, all of which you recognize, their identities are there within, in the same locations as the objects. So an object made of a certain size, and in a certain spatial location, and colored black and brown, is painted with bootsness, and that is what makes it boots. If I mis-paint it as cat, that is what makes it cat - nothing about the lower-level qualia, the shapes or the colors or the general configuration of the object's visual structure, are really directly associated with that meaning. You can destroy certain parts of my brain, and I will still see things as objects, but I won't know what they are.

So, these instances of mistakes in identification are interesting in how they reveal the dissociation between objects in themselves, and objects as they have meaning. An object in itself is still a perceptual construct, but it is meaningless. It only as existence in relation to other perceptual constructs. This is a middle place between the physical stuff to which the object presumably refers, and which is even more meaningless in that it has no relations at all to other stuff - there is simply stuff, and any effort to clump it into this stuff or that stuff is exactly that: effort, something done by an agent. So the object in itself is the way the brain deals that stuff into a usable form, and the meaning of the object, what the object is, is the set of all known relations of the object in higher levels: past and future, the stuff of cogitation and memory, beyond perception that exists only in the immediate moment.

That's enough of this. Just been thinking about these things on the train lately, needed to get it out of my system (or at least articulate it into something interesting - the discrimination experiment based on actual instances of deja trompe might actually be a good idea).

Tuesday, September 03, 2013

false features in text

spent the morning reading papers. there was an interesting exchange in JOV about what was probably my favorite paper of last year; the exchange strengthened my opinion of the paper, but i'm not going to go into it now, because this post is irrelevant to the actual substance of the articles in question.

here's what i saw/see (in the letter-to-editor attacking the paper in question, as displayed in my browser):

[if you want to see it, keep fixating this line, but attend to the lower part of the text below].


Do you see it? I need to ask around. I notice these things a lot, but they're never as salient as this. In case you don't see it, here's an illustration:


There you go. Go back to the first one and see if you don't see that arc. I only see it peripherally (had to draw that line in without looking at it), but scale isn't so important, and neither is field location (so long as it isn't central). The left eye sees it better than the right, and it's stronger overall with both eyes. To me, it's so salient as to be distracting. I had to do all these tests to convince myself it wasn't a retinal tear or something.

(also interestingly ironic is that the paper(s) in question are all about measuring threshold-versus-noise functions, which are shaped just like the illusory/actual line.)

It's apparently just accidental peripheral concatenation of the structure of the letters and words in the paragraph - crowding, basically - but really, if you look straight at the texture, it's damned hard to see just what is stimulating this process, and why it isn't happening everywhere. But it's neat - basically, a positive effect of crowding or lateral interaction, which is usually held up for its negative (destructive) effects.

Also, I think this qualifies as a deja trompé. Haven't had one of those in a while.

Thursday, March 28, 2013

boiling

1. Standing by the stove the other night, waiting for a kettle of water to boil - as it does, starting from the near-silent rattle through the increasing racket, and the whistle starting, and all the other noises that accompany that moment, I had the distinct feeling that I was hearing the big chromatic crescendo at the end of Prokofiev's great D-minor Toccata, one of my favorite piano pieces. It's not that I was fooled - this was not an auditory deja trompé, but something similar - but I've never felt a piece of familiar music so strongly evoked by some random physical event. It was definitely primed by having listened to that piece something like 10 times in the past week. Now whenever I hear that piece, when it gets to the silence at the end before the crescendo, I will think of a boiling kettle.

2. Horrible problems with the paper I've been working on and hoping to have submitted in a matter of days. A big part of the paper - the way that I interpret the data, basically - is a set of relatively simple contrast perception models which I run through the experiment as tests of different hypotheses. I had calibrated these to a set of human thresholds, which I was never quite comfortable with for various reasons, but that's the way I had done it; as a final touch to a figure, I decide to go and generate thresholds estimates for the 'best' model, to plot against the human data, just to show how similar they are, and when I go to do this, the model starts giving me imaginary numbers, which is bad.

By the time I figured out what was wrong - it wasn't really a problem, I was just not using my code properly - I had decided that calibrating the model to the thresholds for my humans was probably a bad idea, because the way I measured the human thresholds was kind of weird, and I could be sure of simulating these properly, so I should just use some standard thresholds. Why not? Nobody is going to argue with a standard CSF. So I plug a standard in and - and I'm going to note here that every time I do something with this model, I have to go and recompute the simulations, which takes hours - and it all goes haywire. The model that 'works', and that's consistent with all these nice facts that I've lined up and made a nice case out of, still works, but depending on how I implement the change in sensitivity, the alternatives either perform horribly - which you'd think is okay, but really doesn't look plausible, just makes it look like I haven't given them a fair chance - or they come out reasonably similar to the favored model.

So, I have to be fair, at the same time that I don't want everything to fall apart. I am certain that things work the way I think they do, and I'm prepared to be wrong, but if I'm wrong then I don't understand how I'm wrong. And building evidence either way progresses in these multi-hour steps in between which I'm sitting here with a stomach ache because I'm afraid that I'm going to wind up with evidence that my experiment isn't actually that good at discriminating these different models.

The problem seems to be in the low-frequency filters; the lowest frequency filter is basically four points in the Fourier domain, and it happens to take up a disproportionately huge amount of image contrast, so the 'not working' models tend to be uniformly low-pass in the simulation, which I know is not fair, because it's all because of that low frequency channel. So I figured that, since these are 'sustained' stimuli, I would be justified in just taking out the lowest few channels and leaving the top 5 or 6 band-pass channels - one thing here being that I'm not willing to go back and redesign everything to the point where we have low-frequency DC-sensitive channels. But then when I just have the mid-to-high frequency channels, the three models are too similar, which I don't like either, and which I know is just because I'm now allowing the low s.f. to get through. And I also know that this version, even though it has the 'standard' CSF, doesn't really because the lowest channels are shut off. So I turned them back on and changed the gain to the CSF, which I realized I had wrong the first time because....

Anyways, you see what I'm doing - changing more than one thing at a time, and making mistakes because I'm rushing it. This just prolongs everything, because every change, or every attempt to figure out what the effects of a change are, and every mistake, takes many hours to evaluate.

Anyways, high irritation and anxiety.

Saturday, January 05, 2013

also

a few other observations from china:

in developed, urbanized places, people live, or aspire to live, in flat, spread-out places (single-family houses in subdivisions, or in the countryside); and they go to work in tall buildings in concentrated, densely-built places.

in developing, urbanizing places, people live, or aspire to live, in tall buildings in densely-built places; and they go to work in flat, spread-out places (factories, construction).

all i noticed was that in china, even in small towns, once you get out of the little villages (where each family has a house of their own), the common people live in tall apartment buildings or highrises, but a lot of them are going to work in huge factory floors, although a lot of them are also going to commercial or service-sector stuff in big multistory buildings. meanwhile in the US, common people (except for young people starting out, or the urban poor, or anyone living in a big city downtown) live in houses surrounded by open space, but they tend to go to work in service sector or commercial business in tall, downtown buildings, although many are also going to work on factory floors. so, it's not a perfect 'economic chiasmus', but still an interesting little contrast.

also, this happened several times: after using the second floor bathroom, i would stand by the window to reassemble my multi-layer winter clothing, looking outside through the blinds. across the street, i would see the front window, at ground-level, of another house, with white curtains drawn. just in front of the window was a little tree with what i think were seed pods hanging from the branches, so that i saw the branches against the window curtain background. each time i saw this scene, i at first would think that the curtain had large-print calligraphic characters printed on it, only to shift immediately to seeing the true depthful scene - deja trompé! even after the shift, there would still be a lingering feeling of 'what are the characters, they are too small to read', which would then quickly disappear as it was obviously a wrong question. it did make me wonder whether or not the same sort of scene had stimulated some artful styles of calligraphy..

Wednesday, December 12, 2012

red boots

m* is visiting the lab, sitting behind me at the desk where p* used to sit. he's leaving friday. i've had several talks with him about methods relating to the blur adaptation studies, and he's really helpful in clarifying certain issues. he's always solidly skeptical.

he has a whole foods paper bag under his desk, i think it's filled with bottles of beer. when you come in the door to the office, if he's sitting there at the desk, you see his back, and the red and brown paper bag sitting on the floor right next to his feet. yesterday, several times, i came in the door and thought immediately i saw him sitting there wearing red cowboy boots, only to realize what i was really seeing. deja trompé!

Sunday, September 30, 2012

中秋快乐!

quick notes for the end of september:

week 1 of bring-your-laptop-to-work was a success; worked steadily in the lab every day, and came home each night to do particular jobs by hand, with pen and paper. extremely effective. laptop came back home friday night; going to continue this for the foreseeable future. should make the next MS revision and the following MS submission much easier.

headache last night, gradual onset; eventually focused pain above right eye socket; photophobia; went to bed, closed eyes, weird eigenlicht flicker, maybe 40-50Hz; what is that? slight headache remnant now, indistinct.

recent weirdness with reading text, usually notice in the morning; right now, left of fixation feels scotoma-like, but i can see there..

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also, a story: when i sit at the kitchen table, in the chair by the window, i have a view of the pantry area, with the fridge and the back door. my leather sandals are wedged between the fridge and the wall, by the door, so i can wear them outside when i go to throw trash out.

i regularly mistake the sandals, peripherally, for Olive the Cat, sitting by the back door, wanting to go out. then i foveate them, and see that they are my sandals. this has happened repeatedly, maybe dozens of times: deja trompé!

Thursday, September 13, 2012

Deja Trompé

When I was in graduate school, I lived in Old Louisville, and walked, most days, down 3rd street to campus. Whenever I crossed the big road separating the neighborhood from campus, Cardinal Avenue, at a certain spot, I would see something up in my right peripheral visual field, and think, "Starlings!"

It was never starlings. It was always the tattered insulation hanging off a bunch of power lines strung over Cardinal. I remember this because even though I learned, pretty quickly, that I wasn't seeing starlings in that instant whenever it occurred, the fastest part of me - whatever part just automatically identifies salient stuff in the vast periphery - always thought that I was.

"Starlings!"

It not that I was hallucinating starlings. A bunch of speckly black stuff fluttering against the sky kind of looks like birds, even when you know it isn't. You can't blame me. I don't blame my visual system. It's an honest mistake. The interesting thing is that I kept making it, over and over again, with apparently no control over it. An inconsequential and incessant perceptual mistake.

I've noticed similar situations over the years, but right now I can't remember the others. I should start making a list. I bring this up because recently someone cleaned out the shared kitchen on this side of the institute, and because I always turn the lights out in the same kitchen.

I think that, because I always turn out the light when I leave the little kitchen, other people have started following my example, and now, often, when I go to the kitchen to get hot water for my tea, the light is already out. This makes me happy. It's happened very gradually. Change is slow, usually.

Usually. Recently, the development office got a new temp who is apparently a complete OCD clean freak. It's great. She cleaned this kitchen and the other one. She put up little signs everywhere telling people not to be such pigs. I love her.

Anyways, now, when I go into the little kitchen to get my water, I stand at the dispenser, watching it to make sure my hand doesn't stray and I don't get scalded, and the microwave with its little sign sits down in my lower left field. Often, lately, the light is out when I get there. I leave it that way, because there's enough light trickling in from the hallway. Every time I am in this configuration, with the light out, it looks for all the world that there is light coming out of the microwave window.

This happens over and over again. It's very robust; I can stand there and look straight at the microwave and its little paper sign, and that's what I see; then I look away, and the sign becomes an emission of lamp light from within the microwave. I can turn the mistake on and off by moving my eyes back and forth.

Again, I don't blame my visual system. It's doing the best it can. I've seen so many microwaves, and when they're cooking, they usually have little lamps inside, so you can see your whatever rotating on the little turntable. If the room is dark, the image is basically of a luminous rectangle in the front door of a microwave. Not many microwaves that I have known have worn little paper signs on their doors. To their disgusting, disgusting peril.

There must be a name for this, but I can't find it. So for now I'm going to invent a term: deja trompé‎, "fooled again". Deja as in deja vu, "again seen"; trompé‎ as in trompé l'oeil, "deceives the eye". Seems like the right flavor for this sort of thing. I'll start keeping track of these, however rare they are. I'll inaugurate the list with a new entry label.

BACK TO WORK