Month: May 2012

Optical Illusions: Our neurons working out of our control

Looking at an image and seeing that something just isn’t quite right is always an intriguing experience. From past experience, we expect to see one thing, but often upon immediate observation we see something else quite different. Optical illusions demonstrate to us directly that reality is created by our perceptions of the environment and these perceptions are processed in our brain. So, maybe reality is just all in our heads?

“Reality is merely an illusion, albeit a very persistent one” – Albert Einstein
(a popular misquotation extracted from “For us believing physicists, the distinction between past, present and future is only a stubborn illusion.”  Einstein: His Life and Universe by Walter Isaacson (2008), p. 540)

Classic examples of optical illusions include the floor tiling at the Basilica of St. John Lateran in Rome and the “flashing” grid illusion first reported by Ludimar Hermann in 1870. The twentieth century artist M. C. Escher took the phenomena to an artistic level and created some of the most popular and aesthetically interesting illusions, and many more optical illusions may be viewed with an image search.

Rotating Snakes illusion, Copyright A.Kitaoka 2003

In 2003, Akiyoshi Kitaoka, a professor of psychology at the Ritsumeikan University in Kyoto, Japan, designed a new visual phenomenon called the peripheral drift illusion, or “Rotating Snakes” (read the original report, PDF). In this design, an apparent motion of the image is seen in the observer’s peripheral vision. The effect is strongest when the image contains clearly graduating sections of repetitive diminishing or increasing brightness and these sections follow fragmented or curved edges. A variety of examples of the design can be previewed on Kitoaka’s website of Rotating Snakes.

This visual phenomena has fascinated scientists with the challenge to explain how our brains process this image. It was not until quite recently that an answer may have been experimentally discovered (“Microsaccades and Blinks Trigger Illusory Rotation in the “Rotating Snakes” Illusion”, Otero-Millan, et al. The Journal of Neuroscience, 25 April 2012, 32(17): 6043-6051; doi: 10.1523/​JNEUROSCI.5823-11.2012, Read the abstract). Researchers from the Laboratory of Visual Neuroscience at the Barrow Neurological Institute in Arizona, lead by  Dr. Susana Martinez-Conde, presented “Rotating Snake” images to participants while recording their eye motion with high-resolution. Previously, it had been presumed that the eyes were drifting during observation to create the apparent motion. However, they instead found that when the observers acknowledged motion in the images, their eyes were undergoing small rapid movements called microsaccades. These mini-eye movements represent small jumps in a person’s gaze position that help to refresh the input on retinal receptors during the intentional fixation on an image (“Toward a model of microsaccade generation: The case of microsaccadic inhibition” Rolfs, et al. Journal of Vision, August 6, 2008 vol. 8 no. 11 article 5 doi: 10.1167/8.11.5, Read the full-text PDF).

It is quite amazing to gaze at an image that you consciously know is static, yet you unquestionably see an apparent animation. Your understanding of reality conflicts directly with your observation of reality. For a quick personal experiment to see if I could control this reality distortion, I was able to temporarily pause the motion with a very focused attempt to stare only at one corner of the Rotating Snake image. As I let my focus shift just bit, the rotation immediately re-appeared. It is only a guess as to whether I was inhibiting the microsaccades of my eyes, or if I was positioning the image in some “peripheral blind spot” where the retinal receptors taking input from the eye motions couldn’t receive the input. Nevertheless, I do still feel quite grounded in reality; however, I am reminded to maintain an appreciation of questioning what I directly perceive around me as my brain will continue to work in ways that is beyond my conscious control.

The 2012 Annular Solar Eclispe

 On Sunday, May 20, 2012, the Moon passed directly in front of the Sun offering a memorable view of an annular solar eclipse from southeast Asia into the western United States.

Path of Annular Solar Eclipse May 20, 2012 - Wolfram Alpha
Path of Annular Solar Eclipse May 20, 2012 - Wolfram Alpha

Here in Central Illinois, Dynamic Patterns Research was unable to witness the solar eclipse thanks to several nice pockets of severe thunderstorms, although we should have been able to see a sliver of eclipse just above the horizon at sunset. Fortunately, many others around the country did have memorable experiences with this special event with great photographs and informal educational experiences with their children. If you would like to re-live the full experience from your home computer, the team at CosmoQuest from SIUE provided a live three-and-one-half-hour feed with commentary and video covering the entire event:

The digital social world was filled with sharing of solar eclipse images, some quite aesthetically outstanding and awe-inspiring. Check out the album from Space.com and the album from Spaceweather.com to witness this great natural wonder of our solar system by talented citizen scientists and enthusiasts from all over the world.

Certainly, a solar eclipse can inspire adults into a greater appreciation of this wonderful universe, but an event like a solar eclipse can offer something a little more special to children. I seem to recall many years ago (well, not that many) during my pre-school days playing outside in the playground when the world grew a little darker and the teachers thoroughly reminded us to not look directly at the sun. The memory is mostly a haze, but I almost think I was a bit scared. Maybe I didn’t understand what was going on, or I was just afraid that I might go blind. What I didn’t have back then was a guided informal educational experience that I was certainly primed and ready for. Moments like these are brief, but critical, for exciting and intriguing young brains about science and helping them develop an appreciation for how everything around us works.

The Geesamans testing their home-made viewer before the eclipse - May 20, 2012Kate Cormeny Geesaman spent the afternoon experimenting with her children building a solar eclipse viewer and then giving it a try at their home in south-central Texas. 

“I think I may have seen a slight sliver “on” the sun, but it wasn’t the dramatic viewing I had imagined. But, Aaron was introduced to the idea and we had a great time in the beautiful Texas weather with our family and neighbors! After we went inside we got our SkyMap app open on our phone and observed how the moon was indeed in front of the sun…just below the horizon.”

Kate Geesaman and son observing the solar eclipse - May 20, 2012

Although Kate and her children were unsuccessful in creating a clear observable image of the eclipse, the experience was certainly invaluable for bringing a bit more curiosity to her young boys, and teaching them something about how to create tools to solve problems — an evolutionary essence of being a human. And, spending time with family, friends, and science makes for a perfect Sunday afternoon!

If you have any images that you would like to share, please post to the Dynamic Patterns Research Facebook page and we’ll be sure to feature your work to everyone.

Unfortunately, Dynamic Patterns Research missed out on making our own direct observations of the annular solar eclipse, but the next opportunity will be perfect, weather permitting of course. We’ve already set our calendars for Monday, August 21, 2017 when the path of the eclipse will be nearly directly overhead, so a “ring-of-fire” image should be possible.

The next annular solar eclipse over the United States, Monday, August 21, 2017 - Wolfram Alpha
The next annular solar eclipse over the United States, Monday, August 21, 2017 - Wolfram Alpha

Be sure to “Like” our Facebook page and subscribe to DPR to be the first to see our images of the eclipse in 2017!

Last updated April 5, 2020