Take a look at this short video clip. Can you tell which dot is blue and which is yellow?
Unless you have a rare vision impairment, this task should be easy for you. But read on, and we'll show you how you can become blind to this difference in as little as 40 minutes.
The human visual system is amazingly adaptive to eye movements. Consider this: if you film a video from a moving car, the resulting image is so jiggly that it's unwatchable. But if you're riding in the car, even on a bumpy road, the outside world appears stable and smooth.
Or take a camcorder and move it quickly from point to point in a room, "looking" at ten or so objects in rapid succession. The resulting video will be a blurry mess. But perform the same experiment using your own eyes, and everything remains in perfect focus, your picture of the world undisturbed by all that extraneous motion.
What's more, the human perceptual system can use motion to build a better picture of the world. By moving your head back and forth, you can quickly learn which of two objects is is closer to you.
But while repeated experiments on eye motion have helped psychologists develop a detailed understanding of how we perceive objects in space, efforts to understand the impact of eye movement on color perception have been less fruitful. In 1962, Ivo Kohler had a single subject wear special goggles for 60 consecutive days. Each lens was split between two colors, right and left, and at the end of the experiment, the subject had a different perception of "white" when looking to the left compared to looking to the right.
In the ensuing years, however, larger studies were unable to duplicate Kohler's results, even after periods as long as 146 days. Now, four decades later, a new study by Aline Bompas and J. Kevin O'Regan may have uncovered the key link between action and perception of color.
In their first experiment, Bompas and O'Regan asked three participants (including Bompas herself) to wear glasses similar to Kohler's goggles, half of each lens tinted yellow and half tinted blue for four hours a day. As you can see by this photo, they weren't going to win any fashion awards:
At the end of each day the participants removed the glasses and attempted to do the task we showed you at the beginning of the article. Since blue and yellow are "opposite" colors, when you first remove a pair of yellow sunglasses, the world appears blue, while removing blue sunglasses makes the world appear yellow. Participants who were wearing glasses shaded yellow on the right hand side looked at the video and were more likely to say the two dots were the same.
For the first time in 40 years, someone had duplicated Kohler's result. Eventually Bompas and O'Regan were able to find the effect after just 40 minutes, by asking participants to wear the glasses and look at a training task requiring them to judge the relative size of dots like this:
The real goal here was just to ensure that participants looked through both the yellow and blue portions of the lenses. After removing the glasses and returning to the color-judgment task, their results were the same as those who'd worn the glasses for four days.
Bompas and O'Regan argue that the eye movement is the key to this phenomenon, a notion supported by a final experiment. In this version, they conditioned participants as before, but during the testing phase, instead of viewing a sequence of dots, viewers looked at a single dot, either to the left or right. This time, there was no difference in the perceived versus actual color of the object, regardless of where it appeared.
Why might our eyes rely on their own motion to perceive colors? Researchers in the late 1990s and the early part of this century may have an answer: cones, which enable color vision, are not evenly distributed across the retina. While many areas have three different cones, long thought necessary for accurate color vision, there are also large patches with only two types of cones. When a single individual has only two different cones, they are "color blind" -- unable to detect differences between certain colors. According to this line of reasoning, if portions of the eye are similarly "color blind," the only way for us to perceive colors consistently is if the visual system can adapt, in much the same way as Bompas and O'Regan's participants do in the study.
Bompas and O'Regan end their study with an intriguing notion: the glasses themselves shouldn't be necessary for the phenomenon to be observed; systematically controlling eye movements by asking an observer to repeatedly look at different colored patches (for example, yellow on the left and blue on the right) should achieve the same effect.
Greta and her research assistant have tried the experiment on themselves, without the glasses, each of them watching over 400 sequences like the ones shown above. Sure enough, they were able to change their perception of yellow and blue without even using those snazzy goggles.
Bompas, A., & O'Regan, J.K. (2006). Evidence for a role of action in colour perception. Perception, 35, 65-78.
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I don't work in vision at all, but I have to say that some of the recent work in vision and consciousness of perception is truely remarkable stuff. O'Regan and Noe's BBS paper (http://www.bbsonline.org/Preprints/ORegan/Contents.html) is fascinating reading about how we perceive the world, and is highly recommended. It's non-technical and is readable by anyone in the cognitive sciences or a layperson with an interest in these sorts of things...
The basic empiricism is fine, but their incredibly lame and self contradicting assertion that experience is done and that qualia is an illusion is absolutely uninspired and lacking any merit whatsoever.
My guess was that the words regarding philosophical issues were a stopgap afterthought secondary and unimportant issue to the authors, whose primary interest certainly wasn't properly engaged in the philosophical issue.
The entire "explanatory gap" of qualia is in reality the BEST that we have till now been able to articulate regarding something which fundamentally eludes empirical data and its functional contexts.
Too bad some people don't discover early on just how real the mysteries are with every new scientific breakthrough and wider progressive push.
The author(s) are oblivious and need remedial study in what philosophical issues their work engages.
Harlan, that's quite an article you linked. Consciousness is a fascinating issue for me, but I can only view it as a layman. The way I see it, it's still much more the realm of philosophers than psychologists.
I suppose I can relate it to this article in the following way: isn't it amazing how much of the visual process we're not conscious of?
Snazzy glasses indeed.
Where does one acquire such snazzy glasses?
RJDuberg is right. Sorry Harlan, but O'Regan and Noe have a minority perspective in human vision research for a variety of reasons. The main reason, however, is that their framework is based upon an old assertion that the human brain does not store internal representations of the external world. Instead, as the authors state in that paper (and many many others, if you're familiar with their work), the world itself functions as an external memory source. It's a nifty explanation, except it doesn't work. In change detection tasks, participants are able to maintain representations of both pre and post-change objects, even though they occupied the same space (Mitroff, Simons, and Levin, 2004).
Furthermore, iconic memory research (Sperling, 1960) also indicates that more of the world is represented than we might expect given a lot of research on the 'inadequacy' of human vision. Finally, there's too much neurophysiology data out there to support the idea that we passively process visual stimuli to the point of semantic categorization to agree that vision is, as O'Regan and Noe believe, a purely active process.
Their perspective is an offshoot of Gibson's theories of perception from the 60's, which was very useful in shifting research toward more ecologically valid paradigms, but hopelessly strict in its limitations on human visual processes. A hybrid model will always provide the best explanation: Human observers represent quite a bit of the world internally, but these representations are fragile. Actively seeking information from objects in the world is indeed very important, but there is little evidence to support that it is exclusively responsible for what we experience as "seeing."