Friday, September 07, 2007

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?


Genius said...

I think I do.
A series of irregular shapes - not really circles but somewhat circular expanding out from the point where I am looking.
Some control over how they expand and where they appear seems to be possible. they also seem to quite often have a thin outside line that is a bit brighter.

Would that be the same phenomenon?


Eric Schwitzgebel said...

Hey, cool. Thanks! It sounds like its in the ballpark. The descriptions vary a bit....

Justin Tiwald said...

Hmm. I don't see them, and I decided to give it a try before reading the last half of your post.

The Goethe? Huh. I wouldn't have guessed it.

Eric Schwitzgebel said...

Thanks, Justin. It's useful to have negative reports, too!

Yep, *the* Goethe. He wrote a book on color that's widely viewed as a vain and quixotic attempt to attack Newton's color theory -- but along the way, he produced some interesting subjective reports about visual experience.

Genius said...

I play with those shapes constantly before I sleep so they are pretty familiar to me.

Eric Schwitzgebel said...

I wonder, Genius, how much the variation in reports is due to real individual differences in experience and how much is due to errors of introspection on one side or the other. Also, if the differences are real, I wonder how much they reflect suggestion, control, and habit vs. how much they're more purely organic or passively perceptual.

No one has ever really sorted out those questions....