When in Paris it is expected that you will see the Mona Lisa at the Louvre and the famous paintings and sculptures at Musée d’Orsay; but what I did not expect was to attend an exhibition full of manipulated light, motion, and optical illusions. The Dynamo exhibition at the Grand Palais completely exceeded my expectations and quite literally messed with my perception of reality.
Location of Dynamo Exhibition
What I would see in person did not match what my camera lens saw and often I would see images that seemed to move or change when I looked from a different angle. One of my favorites is shown in the image below:
Optical Illusion from the Dynamo Exhibit
Unfortunately I didn’t take the best picture so it doesn’t quite work now, but at Dynamo when I stared at the center dot and rings, the outer light blue ring disappeared! Of course my initial reaction was to jerk my head (thinking I was seeing things, or not I guess in my case) and the ring reappeared. This ended up being the intention of the piece and being the nerd that I am, I wondered how they did it.
I did some research and found out that the phenomenon is called Troxler Fading, which is when you are fixating on a central object and the object in your peripheral vision fades away from your awareness. Essentially your brain gets used to seeing the unvarying objects and fades them out so you can focus on the central object. It’s similar to when you drop something in your lap, you feel it for a few seconds, and then forget it’s there until you feel it again when you move. It is the body’s way of reducing sensitivity to constant stimuli, freeing attention to process the new things. The diminished response to a repeated stimulus is called habituation (Lou, 1999).
One very interesting paper I found linked visual habituation (the fading) to adults with ADHD. But first to understand the paper I had to understand how and where the Troxler Fading occurs. Troxler Fading involves two major parts of the brain, the frontal lobe and the parietal lobe. When the parietal lobe was damaged, objects in the peripheral would fade faster than those with a functional parietal lobe. In contrast, those with damaged frontal lobes rarely experienced any fading. The conclusion was that the parietal lobe is necessary to maintain an image, but the frontal is important for the habituation of an object (Mennemeier et al., 1994).
Jacqueline Massa and Illyse O’Desky knew that people affected with ADHD have abnormal frontal lobe activity and wanted to see if their visual habituation was affected. Since the damage to the frontal lobe was linked to no visual habituation, people with ADHD could have a diminished ability to fade out the unimportant things and therefore have a harder time focusing on one task. They used several tests with Troxler fading, asking 21 adults with ADHD to indicate when the dot in their peripheral faded away. The results of the study showed that adults with ADHD had to stare longer to get the dot to fade (habituation) than those without the disorder. They concluded that the impaired habituation may explain why adults with ADHD have such a hard time focusing on one thing at a time; it takes longer for their brain to fade out unimportant stimuli (Massa and O’Desky, 2012).
Nerdy tangents like this are completely normal for me. I see (or don’t see) something and have an urging desire understand it. Most of the time I end up finding cool ways to link it to other things. And now when I take my sister to the exhibition in July, I can explain to her how it all works, even though I’ll probably be the stimulus she fades away…
~Sarah Harrington
References:
Lou L (1999) Selective peripheral fading: evidence for inhibitory sensory effect of attention. Perception 28:519-526.
Massa J, O’Desky IH (2012) Impaired visual habituation in adults with ADHD. Journal of attention disorders 16:553-561.
Mennemeier MS, Chatterjee A, Watson RT, Wertman E, Carter LP, Heilman KM (1994) Contributions of the parietal and frontal lobes to sustained attention and habituation. Neuropsychologia 32:703-716.
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