Barberpole Illusion

The barberpole illusion is an example of illusory motion perception by our brain. This pole was usually displayed outside barbershops (hence its name), and consists of a pole with diagonal stripes (they can be of different colors) rotating horizontally (around its vertical axis).

When observed, even though the stripes are moving horizontally, our brain perceives them as moving vertically in a straight, neverending line. The direction perceived (top-down or bottom-up) depends on the rotational verse (clockwise or anticlockwise) and is consistent (objective) in all people.

Barberpole Illusion: the stripes seems to be moving along the vertical axis, but they are in fact rotating

A smaller, simplified version of a rotating black-and-white barberpole