Keep Your Eyes on the Cross
Why this is Happening?
Your eyes like change.
The effect in this illusion is based on the fact that your visual cortex, the vision center of your brain, is always trying to find new information. Information that is determined to not be new is essentially ignored. This habituation, as it's called, occurs even over very short durations. Your visual cortex determines that what it's seeing is "normal" and it expects that to stay the same. When that "normal" becomes something different, your brain exaggerates the difference between its perceived "normal" and what you're actually seeing.
You'll notice that there is a lot of variance in the shapes of the faces you see and the shape and size of the features. When your brain adapts to a person with a round, thin face, if the next person has a wide, square face then it looks even wider and squarer.
If a nose is slightly crooked in one image, it will look crooked the opposite direction in the next image, because your brain expects "crooked to the left" to be normal. Anything that is not "crooked to the left" must be crooked to the right.
It occurs when you're looking at the dot cross because moving your eyes resets this effect (which is why it doesn't happen in everyday life), and because your peripheral vision is better at determining general shapes rather than details. Your peripheral vision looks at the general shapes of these faces and warps your perception to match those general shapes to what it expects them to be. If those faces were right in front of you, it would be 1) harder to keep your eyes focused on one point because of all the dramatic change directly around that point, and 2) easier for your brain to look at the details and adapt to the differences.
It should be noted that this habituation effect also contributes to the reason why illusions such as inverted color illusions work (notice that when you move your vision the color goes away). Your brain adjusts to the colors, and when they change suddenly your brain exaggerates the difference.
My Reaction after watching this.
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