MIT Press BITS

One reason I'm a fan of MIT Press (the publisher of both of my books) is that for an academic press their prices are very low (my 2011 book is currently $14.21 at Amazon) which means that a broader range of people can afford the book than if it were at another press. Another reason I'm a fan is that MIT has tended to be a leader in exploring new electronic media.

So it's very cool that they've chosen a chapter of my Perplexities of Consciousness for their BITS project, a new enterprise which allows people to electronically buy a portion of an MIT Press book for a low price ($2.99 in this case) and then later, if the reader wants, the whole book for 40% off list price. The chapter they've chosen is "When Your Eyes Are Closed, What Do You See?", which although it is the eighth and final chapter of my book, does not require that the reader know material from the previous chapters -- thus, a reasonable choice for a BIT.

What I'd really love to see down the road is a model where you can buy any selection of pages from a book for a nickel per page.

When Your Eyes Are Closed, What Do You See?

I've drafted the eighth and final chapter of my book in progress (working title Perplexities of Consciousness). Chapters 4 and 7 are not yet in circulatable form. Like the other chapters, this chapter is written to be comprehensible in isolation. As usual, I welcome feedback, either by email or as comments on this post. Unlike the other seven chapters, this chapter is not based on a previously published article.

Here's an abstract:

This chapter raises a number of questions, not adequately addressed by any researcher to date, about what we see when our eyes are closed. In the historical literature, the question most frequently discussed was what we see when our eyes are closed in the dark (and so entirely or almost entirely deprived of light). In 1819, Purkinje, who was the first to write extensively about this, says he sees "wandering cloudy stripes" that shrink slowly toward the center of the field. Other later authors also say such stripes are commonly seen, but they differ about their characteristics. In 1897, for example, Scripture describes them as spreading violet rings. After Scripture, the cloudy stripes disappear from psychologists' reports. Other psychologists describe the darkened visual field as typically -- not just idiosyncratically, for themselves -- very nearly black (e.g., Fechner), mostly neutral gray (e.g., Hering), or bursting with color and shape (e.g., Ladd). I loaned beepers to five subjects and collected their reports about randomly sampled moments of experience with their eyes closed. Their reports were highly variable, and one subject denied ever having any visual experience at all (not even of blackness or grayness) in any of his samples. I also briefly discuss a few other issues: whether we can see through our eyelids, whether the closed-eye visual field is "cyclopean", whether the field is flat or has depth or distance, and whether we can control it directly by acts of will. The resolution of such questions, I suggest, will not be straightforward.

Thanks very much, by the way, to all the people who wrote about their eyes closed visual experience in response to my queries about it in earlier posts.

Eyes Closed Visual Experience -- Subjects 3 and 4

In two previous posts, I described the visual experiences reported by two volunteers who wore random beepers while keeping their eyes closed in various environments for at least two hours a day over the course of 3-4 days. Subject 1 reported sensory visual experience in only 25% of his samples, and of only a fairly uniform black or orange field. In the majority of his samples, he reported no experience whatsoever -- not even of blackness or neutral gray. Subject 2, in contrast, reported visual experiences, often complex and detailed, in every single sample.

Subject 3 (an administrative assistant here at UCR) stood somewhere between Subjects 1 and 2, reporting visual experience in 9 of her 12 samples. When she was in a dark environment (4 samples), she described her experience as slightly differentiated blackness with a little bit of motion in it, like the turbulence of water about to boil. In lighter environments (5 samples), she consistently described her visual experience as like a sea of yellow-white or gray swirls. In one sample, these swirls were accompanied by a dark afterimage of something she had been looking at; in another, by dark and light spots. In those samples where she reported no visual experience whatsoever, she was either very deep in thought (2 samples) or asleep (1 sample).

When I pressed her about the spatial characteristics of her eyes-closed visual field, she resisted attributing it any properties of depth or distance. (Well, at first, she said the distance was something like arm's length, but then she retracted that.) She said the field seemed broader than tall, and to extend about to the range of her ordinary eyes-open peripheral vision.

Subject 4 (a retired economist) reported no sensory visual experience whatsoever, in any sample, not blackness, not gray, not colors or faces, and no visual imagery either -- nothing visual at all, whether he was out in the sun or indoors playing piano or listening to the radio. When he closed his eyes in my office during the subsequent interviews and thought about his visual experience as it was ongoing, he reported some visual experience (of darkness or the like), but he insisted that his eyes-closed consciousness in the sampled moments was not like that. He no more had a sense of darkness when the beep went off than he had a sense of the presence or absence of magnetic fields in the room. He did think he sometimes had visual experience with his eyes closed, during the experiment -- but never in the random moments at which he was beeped.

The Mysterious Disappearance of the Wandelnde Nebelstreifen

In 1810, Goethe, in the first book primarily on the subjective phenomena of vision, described "subjective halos" or successive rings or circles seen in nighttime darkness. In 1819, in the next great study of the subjective phenomena of vision, Purkinje gave a detailed description of these wandelnde Nebelstreifen (shifting fog-ribbons), seen in the dark visual field with the eyes closed. He even drew pictures:





Here's his verbal description:

If I keep the eye in darkness without any outside light, then sooner or later weak dawning, delicate, hazy objects begin to move; at first unsteady and formless, then gradually forming into something more definite. The general case is that the forms are spreading, more or less curved ribbons, with black intervals lying between, either as concentric circles moving toward the center of the visual field, and losing themselves there, or as changing curves breaking against themselves and curving together into themselves, or as bent radii that move around in circles. Their movement is slow, so that for me it usually requires eight seconds for such a ribbon to complete its course and fully disappear. Never is the darkness, even in the beginning of the observation, perfectly pure, always there floats a chaos of weak light (1819, p. 74).

The next great scholar of subjective visual phenomena, Johannes Mueller, described something similar:

If one observes the visual field with closed eyes, then one sees not only sometimes a certain degree of illumination in it, but also sometimes brighter glows, sometimes spreading circular waves, which develop in the center and disappear in the periphery. Sometimes the glow appears more cloudlike, foggy, spotted, and rarely repeating itself for me in a certain rhythm (1837, vol. 2, p. 391).

Helmholtz (1856) and Aubert (1865) describe similar phenomena -- but unlike Purkinje and Mueller they do not emphasize the wandelnde Nebelstreifen over other phenomena of the darkened field.

Many other scholars described the darkened visual field in the late 19th and early 20th centuries, and there are some later 20th century descriptions I've found, but almost none mention spreading or collapsing rings. The last clear reference I can find that's not merely a report of earlier findings is Scripture (1897). (Ermentrout and Cowan (1979), though, do mathematically predict concentric circles and spirals as one common form of visual hallucination, given their mathematical model of that phenomenon. HT: Gualtiero in his comment here.)

So, where have all the wandelnde Nebelstreifen gone? (Cue the violins, or maybe Dylan.) Did Goethe, Purkinje, Mueller, Helmholtz, and Aubert see something that others experienced but failed to notice? Did people stop experiencing wandelnde Nebelstreifen for some reason? (Maybe Goethe suggested them and then later readers unwittingly created them, until that early work was forgotten?)

Like black and white dreams and the elliptical appearance of obliquely viewed coins, and seeing everything double that's not at the same distance as the visual point of focus, wandelende Nebelstreifen seems to be a culturally specific phenomenon of sensory experience -- or at least sensory experience reportage.

Do you see them?

Eyes Closed in the Sun

Okay, I confess, I'm obsessed. I've been trying to acquaint myself with the whole history of phenomenological reports of visual experience (excluding imagery experience and afterimages) with one's eyes closed. I've been running subjects and bothering undergraduates and Philosophy Department staff. I've even opened a new blog category: eyes closed.

Today, among other things, I obtained two reports on visual experience while facing the sun with eyes closed. Reviewing almost 200 years of literature, I've amazingly never found an attempted replication of Purkinje's 1919 report that "most people" see checkboard figures under these conditions. Here's a figure drawn from his own experience:



I don't think I've ever seen such checkerboard or latticework figures in the sun! (And now, of course, I've tried several times for extended periods.) I gave four people beepers and asked them to sit in the sun; only two, I think actually did face the sun directly, and one reported a Purkinje-like "honeycomb" visual experience in a couple of cases, while the other reported no such thing.

So today, I coaxed two people to stare with closed eyes directly at the noontime sun for seven minutes (independently, one after the other), while I collected blow-by-blow reports. About halfway through each observation, I explicitly asked them if they saw any checkerboard or honeycomb-like figures.

The observers' reports were very similar: Both reported bright fields fluctuating in color from red to orange or yellow or white. Both reported the field as pretty uniform, apart from some perturbations (one reported diagonal lines that came and went, the other reported squiggles and lighting-like branching figures), and possibly a bit darker toward the periphery. Both explicitly denied any checkerboard, latticework, or honeycomb-like shape.

These reports are very similar to what I recall experiencing myself, though I believe I in no way suggested anything like this to the observers. When I invited him, the first observer said he knew what he would experience -- a bright red spot in the middle of his visual field -- and he was surprised to have to report otherwise.

Yet Purkinje's language about this is very strong:

Furthermore, I must mention that the described figures, especially the little squares, were noticed by most individuals with whom I made the experiments, insofar as, without drawings, it was possible to get an imperfect report through words.

They would come, therefore, not merely to particular individuals under quite special organic conditions, but rather would be grounded in general conditions of the organism or even in all subjects due to physical laws.

Curious!

[Update, Sept. 10: I've just discovered a translation of this passage in Purkinje (Wade & Brozek 2001) and I think I may have got a key phrase and idea wrong. It looks as though Purkinje thinks that one must maintain a fast waving of the fingers and that this is key to the phenomenon, which is almost stroboscopic. Helmholtz 1856/1909/1962, vol. 2, p. 256-7, reports similar phenomena; as do Smythies (1957) and others in discussion of "stroboscopic" effects....]

Eyes Closed Visual Experience -- Subject 2

What, if anything, do you visually experience when your eyes are closed? Historical reports are diverse (some of the most detailed are Purkinje's, partially translated here). So are casually collected contemporary introspective reports. To get some more data, I gave five people random beepers to wear while keeping their eyes closed for extended periods. About a week ago, I described what Subject 1 said was going on visually with him at the last undisturbed moment before he was beeped. Today, Subject 2.

While Subject 1 reported sensory visual experience in only 4 of his 14 samples (and visual imagery in many but not all of the rest), Subject 2 (who, like Subject 1, was a male graduate student in philosophy) described sensory visual experiences in all 10 of his samples. This immediately prompted me to wonder: Does Subject 1 really have relatively little visual experience when his eyes are closed, or did he simply forget his experience? Did Subject 2 really have visual experience in every single sample, or did he unwittingly fabricate some post hoc, after the beep occurred? Do you think you always have visual experience when your eyes are closed? Or does the experience fade away entirely when your mind is on other things? People appear to have divergent intuitions on this question.

When Subject 2 took his samples in a relatively dark environment, Subject 1 tended to report something like a black/gray wash permeated with varying tones of yellows, oranges, and whites, shifting in intensity but not swirling or moving in an organized way. In some samples one side of the field might be lighter gray or than another or yellowish-orangish (though still, despite the hue, as dark as black -- reminding me of Paul Churchland's "chimerical colors"). Not so different from Subject 1's reports.

Subject 2 also took samples in direct sunlight -- the first was fairly similar to the dark samples, but with more yellow-orange as well as streaks or flashes of light. However, in the remaining sunlight samples, Subject 2 tended to report honeycombs and latticework, and different backgrounds. For example, in one sample Subject 2 reported a bright red field with a large magenta circle in the center, with a darker red honeycomb structure over the whole field.

One reason I found these sunlight reports interesting is that Purkinje in 1819 reported that most of his observers saw checkerboard or latticework patterns when they faced the sun with their eyes closed (see fig. 2 here) -- something I don't recall any other researcher saying, and something I don't think I normally experience. (Do you?) So almost two centuries later, is Purkinje's report being vindicated? I resolved to ask my three remaining subjects to take some samples in direct sunlight....

Eyes Closed Visual Experience -- Subject 1

Over the last year, I've been thinking a bit about visual experience with our eyes closed (e.g., here, here, here, here). A few months ago, I started giving volunteer subjects random beepers and having them keep their eyes closed for two hours a day over the course of three days. After each random beep, they were to note whether they had any sort of visual experience in the last undisturbed moment immediately before the beep, and if so what it was. After each day (about 3-6 beeps), each participant came to my office for an hour-long interview.

Subject 1 was a male graduate student in philosophy who expected not to find any visual experience, not even of blackness, with his eyes closed. (On people's differing opinions about the omnipresence or not of visual experience see here.) He distinguished sharply between sensory visual experiences and visual imagery experiences. (To understand that distinction, keep your eyes open and form a mental image of the front of your house. There's a difference of some sort -- even if only in vividness [per Hume and Perky] -- between that imagery experience and your ordinary sensory visual experience, no?)

Of the 14 sampled experiences we discussed, Subject 1 reported 8 with visual imagery experience only and no visual sensory experience, 1 with visual sensory experience only and no visual imagery experience (the very first sample), 2 with neither sort of experience, and 3 with both visual imagery and visual sensory experience. He did not think his visual sensory experience and his visual imagery experiences interacted at all -- for example, in one sample he reported a visual sensory experience of a uniform, darkish orange field of light with a slight texture (as I understood it, he meant not a textured depth, but a bit of repetitive random variation in the color). He also had complex visual imagery of a former apartment of his. The visual imagery was not tinted orange, nor was it located in space (next to, behind, etc.) relative to the sensory visual experience.

Subject 1 generally reported his visual sensory experience with his eyes closed to be flat, two dimensional, and located in a forward direction, but without any sense of depth or distance. One experience he described as being "black with staticky [colored] swirls"; the rest he described as a lightly textured uniform darkish orange.

In coming posts, I'll describe four more subjects' reports. The big question for me: What patterns will emerge in their reports? What will they tend to agree on and disagree on? Will they all describe their sensory experience as flat? Will they all have the same view of the difference between, and non-interaction between, visual imagery and visual sensation? Will they report relatively simple, undifferentiated visual sensations, like Subject 1's? Like Subject 1, will they report visual sensory experience in only a minority of samples?

Not since the early 20th century has this sort of thing been studied systematically -- not that I have found yet, anyway! -- and early authors diverged considerably in their opinions.

Checkerboards and Honeycombs in the Sun

In 1819, the eminent physiologist Johann Purkinje drew the following picture of what he saw when he closed his eyes and faced toward the sun:



Purkinje said that most individuals with whom he tried this experiment report seeing such figures, especially the little squares. (For a fuller translation of this and surrounding passages, see here.)

When I face the sun with eyes closed it doesn't seem to me that I see checkerboard or honeycomb shapes. Rather, I'd say, my visual field is broadly and diffusedly orange or light gray (slowing shifting between these two colors) -- and brighter, generally, in the direction of the sun. Sometimes it briefly becomes a vivid scarlet. Others I've asked to close their eyes and look at the sun also generally don't report Purkinje-like experiences (although one person on one occasion -- out of several occasions -- reported something like a honeycomb latticework).

So I'm curious: Was Purkinje simply mistaken? Did he have unusual experiences, accurately reported for his own part, and then subtly pressured his subjects into erroneously reporting similar things? Could this be the kind of experience that varies culturally? I'd be interested to hear if any of you experience checkerboards or latticworks.

Seeing Through Your Eyelids -- Spreading Motion

When I close my eyes and wave my hand before my face, I seem to see motion. I think this isn't just the caver illusion (the sense people sometimes have, in complete darkness, that they can see their hands move), because the effect seems much stronger when I face toward a light source, and I can see a friend's hand in the same way. In some sense, I am seeing through my eyelids. This shouldn't be too surprising: Most people report being able to see the sun through their eyelids. Such a thin band of flesh is easily penetrated by light. I discussed this stuff a bit in a May post.

Although I was pretty confused in my May post, I'm finding more consistency now with directional and occlusion effects. If I move my hand slowly from one side to the other, I can locate the position of the movement as to the right or the left. If I face a bright light source and move my head, I can track the rough direction of the source. If I raise an occluding object between my face and my moving hand -- a newspaper, say, held eight inches before my face -- the impression of movement is much lessened. (Any sense of motion that remains might really be just the caver illusion.)

The oddest effect is when I slightly lower the occluding object, so that the tips of my fingers are not occluded, but the rest of my hand and arm is. Once again I have a vivid experience of motion -- but not as though located just at the top of the visual field. The motion seems to spread down the field, almost to the bottom, as though the newspaper were entirely removed, but somewhat less vivid. In fact, it seems to me that the primary effect of moving the newspaper up and down is increasing and decreasing the vividness of the sense of motion. The change in the visual extent of the motion experience appears relatively minor.

As far as I'm aware, this spreading of perceived motion when the eyes are closed has never been remarked on in the perception and consciousness literature. I wonder if others experience the same thing...?

With Your Eyes Closed, Can You See Your Hand in Front of Your Face?

Puzzlement and confusion:

I close my eyes. I wave my hand in front of my face. It seems as though I can see the motion of my hand. Most people I've asked report the same.

It's possible that I do detect that motion. A certain amount of light penetrates the closed eyelids. I could be detecting differences in lighting as my hand passes before my eyes.

But on the other hand, most people, deep in a cave where there isn't a single photon to pierce the darkness, will report being able to see their hands moving in front of their faces. That this isn't a matter of picking up on visual stimulus is made clearer by our inability in such situations to detect another person's hand waved before our faces. It seems that our knowledge of the movement of our hand is somehow affecting our visual experience, or at least our judgments about our visual experience, without actually causing any visual input.

So: When my eyes are closed and I seem to detect my hand, am I actually visually detecting its motion? Or is what's going on more like what happens in a cave?

Let's do some science. Consciousness studies, in such matters, is pretty uncut. Maybe there's something out there on this, but I bet you'd have to dig pretty deep; and then you'd get a few weird articles from 1932 or something, or from a minor Japanese journal in 2001 -- articles that have never been cited, and that have strange, contradictory results. (I don't know this for sure, I'm just conjecturing based on past experience with similar questions.) If so, you can do novel experiments right there in your armchair.

Try facing different directions (toward a light source, away from a light source). Try closing your eyes more tightly, or occluding them with your other hand, or interposing an object between your eyes and your hand. That's what I did at least. I found myself sufficiently puzzled that I dashed downstairs and found a group of loitering undergraduates and had them all do it too! (This probably enhanced my reputation as a kooky professor.)

The results were complete uninterpretable chaos. For example, for myself: I seem to see it more strongly when I face a light source than when I face away. When I close my eyes tightly or put my other hand completely over them, I find myself uncertain about whether I have visual experience conditioned on the motion of my hand. If so, it is less. But when I put an occluding object between my eyes and my moving hand, say six inches in front of my face, I do think I still experience the motion of my hand, despite the fact that it can't be affecting me though that occluding object -- or at least that's how it seemed to me before I ran downstairs. I seem to be able to reproduce that effect only inconsistently. Others had different patterns of results.

If you're game to try, I'd be interested to hear your thoughts and experiences. Maybe I'll even work some of them into a presentation I'm hoping to give at the Association for the Scientific Study of Consciousness next month....

When Our Eyes Are Closed, What Do We See?

Here are some possibilities:

(1.) blackness or a grey haze,
(2.) nothing at all (not even blackness),
(3.) a field of shifting colors,
(4.) afterimages on a background field of black or gray,
(5.) patterns of color, not obviously related to external stimulus, on a field of black or gray,
(6.) visual imagery of objects, maybe like a dream or a daydream or a faint perception or a hallucination?

What do you think?

Last week I asked visitors here and a number of people around UCR. The responses were wonderfully various, and some of them quite detailed, but if I had to summarize or force them into boxes I'd say I got these results:

(1) black/grey (possibly shifting or undulating): 4 respondents;
(2) usually nothing, not even blackness: 1 respondent;
(3) colors: 4 or 5 respondents;
(4) afterimages: 1 or 2 respondents;
(5) patterns of color against a black or grey background: 5 respondents;
(6) visual imagery of objects or scenes: 1 respondent, but 3 others mentioned that they sometimes have this experience or they have it after a while.

Now what's interesting to me in this is the variability in the responses. Do people really experience such radically different things when they close their eyes? I don't think we can dismiss these differences as differences merely in the language used to convey basically the same idea (except maybe between 3 and 5, though even there only in some cases). Could some people simply be wrong about such an apparently easily observable matter?

To bolster some of the less popular responses:

On (2): Many researchers think we don't have conscious experience at all without attention -- for example, when we're not attending to the refrigerator hum in the background, we don't have any auditory experience of it at all. Others disagree. (I've written about this here and posted on it here.) If we go with those who deny experience outside of attention, and if we think that when our eyes are closed we normally aren't visually attending to anything, that lends some credence to (2). Of course, on this view, when I ask you what your visual experience is, and then you close your eyes, your attentional state is atypical and you'll probably experience something. But this may be quite unrepresentative of our visual experience when we're listening to music with eyes closed or when we're trying to fall asleep, etc.

On (1): This response can be buttressed by a related argument. Maybe paying attention to visual experience with one's eyes closed does something to bring out or enliven that experience, with afterimages and shifting colors, but normally, when we're not really attending, its more like a plain black or grey field.

On (4): Early introspective psychologists like Purkinje, Helmholtz, and Titchener, seemed to think afterimages consistuted a major part of one's eyes-closed visual experience. They studied this stuff intensively, so I don't think we should simply dismiss their reports.

Okay, I've managed to completely bewilder myself! Any thoughts about how (and whether) we can make progress on this question? Maybe it's not, strictly speaking, an especially important question. But it's a basic question -- one that's surprisingly hard to find good discussions of, this late in our study of the mind and visual experience.