Neuro-ophthalmology: Why some people see this picture moving and some not!

Recent posts about optical illusions motivated me to share some neuro-ophthalmogical insights.

Look at the picture: is it moving or not moving?

A) The picture is moving

First time I saw this purple and yellow image - from my colleague Prof. Kitaoka - move, it was in Amsterdam. I soon realized it was also moving in other cities ;P

The reason is as follows. Maybe you vaguely remember while napping during the physics class, the teacher suddenly pulled out a glass prism and beamed light on it, creating a beautiful rainbow.

Fig. Chromatic Aberrations (DervalResearch, printed with permission)

The rainbow appears because each color has a different wavelength and is refracted accordingly to a different spot from left to right :

- first purple and blue, which are short wavelengths

- then green, which is a bit undecided in the middle

- and finally yellow and red, which are long wavelengths

Similarly when looking at the picture, the purple will hit our eye at the front of the retina and the yellow at the back of the retina. This phenomenon is called chromatic aberration. Our eyes going back and forth between the two colors create the optical illusion of movement.

B) The picture is not moving

When looking at this picture, an ocular muscle helps the eye change focus: tensing and relaxing, switching from the short wavelength color (purple) to the long wavelength color (yellow).

Some people with strong ocular muscles can go back and forth seamlessly, while others will get borderline dizzy or even do a “technicolor yawn”!

Hope this post will help you choose your colors and/or fitness routines wisely :)

Sources :

Derval, D. (2018). Designing Luxury Brands: The Science of Pleasing Customers Senses. Springer Berlin Heidelberg.

Derval, D. (2010). The Right Sensory Mix: Targeting Consumer Product Development Scientifically. Springer Berlin Heidelberg.