Yet Another Illusion
This is a sequel to my earlier blog, Dr. Jekyll & Mr. Hyde : Consciousness and how we “see” things
Here, I give yet another amazing illusion, and then attempt to provide the "explanation" for this -- and based on this, suggest the way in which our cognition works.
Observe the figure below:-
a) You see a number of pink dots arranged in a circle. These dots would seem to blink in a sequential fashion, giving the impression of clockwise rotation. b) Now, stare at the the black + in the center, and you get to see the "moving" dot as green! c) Keep looking at black + . After a short period of time, the pink dots will slowly disappear one by one, and you will only see a single green dot rotating! Amazing, right? What is the explanation? Try making a few guesses before you proceed to read my explanation.... My explanation:- a) There are 12 pink dots, all of which are stationary. Now additionally, at a much slower rate (12 times in a second?), each dot (by turn) is switched off/ on. It is this sequential off/on that causes the perception (initially) of rotation.
b) When we stare at the central +, the brain re-interprets that what rotates is a green dot (green being "negative" of pink). Why?
The colour changes from pink to green because our nerves get 'tired' (having to continuously re-interpret the colour of the "moving" dot from pink to grey to pink). This has to do with the delay in sodium replenishment to our optical nerves. Reduced input of sodium causes the brain to interpret this to be a colour reversal (pink to green).
c) When we continue to stare at the + in the centre for some time, the still pink dots disappear -- but we continue to see (through peripheral vision) the single "moving" green dot. This happens because in case of peripheral vision, the brain "ignores" still images, but not moving images -- especially when there exists both moving and still objects in the periphery.
d) I experimented by studying the same picture of pink dots by stopping the on/off. (That is, the dots remain always on). When I stared at the central +, the pink dots disappeared, even though there was no rotating green dot! But this took greater effort than when there is a rotating dot. Try this on the picture below.
You can also check that if you stare long enough at a pink dot, and then quickly look at the background grey, you will get to see a green halo around this. Sounds reasonable? If you have come across strange illusions such as this, please share with me. We can try to find the explanations.
Original blog at: http://creative.sulekha.com/yet-another-illusion_246720_blog
Here, I give yet another amazing illusion, and then attempt to provide the "explanation" for this -- and based on this, suggest the way in which our cognition works.
Observe the figure below:-
a) You see a number of pink dots arranged in a circle. These dots would seem to blink in a sequential fashion, giving the impression of clockwise rotation.
b) When we stare at the central +, the brain re-interprets that what rotates is a green dot (green being "negative" of pink). Why?
The colour changes from pink to green because our nerves get 'tired' (having to continuously re-interpret the colour of the "moving" dot from pink to grey to pink). This has to do with the delay in sodium replenishment to our optical nerves. Reduced input of sodium causes the brain to interpret this to be a colour reversal (pink to green).
c) When we continue to stare at the + in the centre for some time, the still pink dots disappear -- but we continue to see (through peripheral vision) the single "moving" green dot. This happens because in case of peripheral vision, the brain "ignores" still images, but not moving images -- especially when there exists both moving and still objects in the periphery.
d) I experimented by studying the same picture of pink dots by stopping the on/off. (That is, the dots remain always on). When I stared at the central +, the pink dots disappeared, even though there was no rotating green dot! But this took greater effort than when there is a rotating dot. Try this on the picture below.
You can also check that if you stare long enough at a pink dot, and then quickly look at the background grey, you will get to see a green halo around this.
Sounds reasonable? If you have come across strange illusions such as this, please share with me. We can try to find the explanations.
Original blog at: http://creative.sulekha.com/yet-another-illusion_246720_blog
Original blog at: http://creative.sulekha.com/yet-another-illusion_246720_blog
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