Monday, August 27, 2007

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....

No comments: