How the portal illusion works

Summary by Krater

Steve Mould examines visual illusions where rotational motion is interpreted by the brain as vertical motion, comparing helical assemblies, barberpole illusions, and moving apertures.

From the video

Answers: Why do certain rotating spirals and patterns look like they are moving vertically?

• Portal illusion
• Barberpole illusion
• Rotational motion vs vertical motion perception
• 3D printed mechanical illusions
• Data privacy brokers

What it concludes

• Rotational motion of a spiral is equivalent to vertical displacement, causing the brain to rely on external clues to resolve the ambiguity.
• Laying a rectangular aperture over moving stripes biases the brain into perceiving vertical downward motion depending on the orientation and shape of the aperture.