WHAT ARE PHYSIOLOGICAL ILLUSIONS?
Physiological illusions are made from the effects on the brain or eyes after being exposed to
something like brightness, tilt, colour, or movement for a certain period of
time.
Lilac Chaser Illusion
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Two illusions occur in this video. After staring at the crosshair for around 20 seconds, all of the fuzzy lilac dots seem to disappear. Also, it looks like there is a green dot moving in a circle, however it is just the dots blinking one at a time.
All of the dots disappear because of something called Troxler's effect. It was discovered in 1804 by a Swiss physician named Ignaz Paul Vital Troxler. The effect happens because our brain becomes less aware of things that aren't changing, and becomes more aware of things that are. In the video, the dots never move while the blinking goes around. This causes our brain to focus on the blank spots while losing awareness of the lilac dots that don't move. Other parts of the human body act similarly as well. For example, when a bug lands on your arm, you feel it at first, but slowly forget about it. You only feel it again when it starts to move.
The light green dot replaces the blinking animation because the retina becomes so exposed to the color lilac that when it disappears, you see it's complementary (opposite) colour instead. In this case, the complementary colour of lilac is light green.
All of the dots disappear because of something called Troxler's effect. It was discovered in 1804 by a Swiss physician named Ignaz Paul Vital Troxler. The effect happens because our brain becomes less aware of things that aren't changing, and becomes more aware of things that are. In the video, the dots never move while the blinking goes around. This causes our brain to focus on the blank spots while losing awareness of the lilac dots that don't move. Other parts of the human body act similarly as well. For example, when a bug lands on your arm, you feel it at first, but slowly forget about it. You only feel it again when it starts to move.
The light green dot replaces the blinking animation because the retina becomes so exposed to the color lilac that when it disappears, you see it's complementary (opposite) colour instead. In this case, the complementary colour of lilac is light green.
After-image Illusion
Stare at this image for approximately 1 minute, then look at the blank surface. The image should appear on the blank surface with inverted colours.
The reason why this effect happens is because the photoreceptors (mainly the cone cells) that are focused on the image adapt and lose sensitivity. When the cone cells lose sensitivity, they don't respond as much. After the eye looks at a blank surface, the adapted photoreceptors send out a weak signal, which prevents you from seeing the colour. While this happens, the cone cells that didn't adapt as much send out a strong signal, which causes you to see opposite colours.
The reason why this effect happens is because the photoreceptors (mainly the cone cells) that are focused on the image adapt and lose sensitivity. When the cone cells lose sensitivity, they don't respond as much. After the eye looks at a blank surface, the adapted photoreceptors send out a weak signal, which prevents you from seeing the colour. While this happens, the cone cells that didn't adapt as much send out a strong signal, which causes you to see opposite colours.