manual

42
The image of the moving spiral stays in the brain which
visualizes movement for a few moments even after the
motion has stopped.
the human brain
This illusion is called motion aftereffect. It is also called the waterfall effect
because when you gaze into a waterfall for a while and then look at the
surrounding landscape, the landscape appears to move upward.
Neurons (cells in your brain) get used to seeing the spinning disk and adapt
to the motion so you can concentrate on other things. For example, when
you put your clothes on in the morning, you notice them touching your
skin; but when you start concentrating on other things, you forget abut
your clothing. Your brain’s neurons adapt to the clothing and don’t respond
(or barely respond) to the sensation of your clothing touching your skin.
Your neurons similarly adapt to the spinning disk image by barely
responding to the motion of the disk. But this puts the brain’s sense of the
motion of surrounding things
out of balance with the way it perceives the
disk motion. The brain compensates by perceiving the stationary
surrounding images (like the clouds on the paper), as moving the other way.
Caution: Some people may suffer ill effects from watching
this pictur
e as it spins. If this activity makes you feel
unwell or pr
oduces the illusion of color
, stop immediately
.
If you suffer from epilepsy or migraines, please consult a
doctor before doing this activity.
neuron
cell body
axon
dendrites