Wednesday, August 29, 2007

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....]

3 comments:

gualtiero said...

did you look at Ermentrout and Cowan 1979 mathematical model of "hallucinations"?

Eric Schwitzgebel said...

Wow, what a neat article! Thanks, Gualtiero. It's fantastic to have readers like you!

Nisha Ahmed said...

I've looked at the sun with eyes closed many times and usually see (or feel? ) a black spot directly over the sun and warm red, magenta, orange hues all around. Sometimes, I see a smaller black spot adjacent to the larger one. No patterns though, except when I physically do something to my eyes or concentrate on certain ideas. Interesting to find out about your observations!
Even more so, I attended UCR , and was just browsing the net about looking at sun with eyes closed and found your blog.