Think your eyes have no trouble detecting when an object changes colour, size, or shape? This new illusion crafted by Harvard’s Jordan W. Suchow and George A. Alvarez might just prove you wrong.
Focus your eyes on the white dot in the centre of the video above. While the dots arranged in each image remain static, their various transitions are quite obvious. When the images begin to rotate, however, those dots suddenly don’t seem to be changing quite as fast, if at all. They are still making the same transitions they were before the motion began; you just aren’t seeing it.
Harvard Department of Psychology graduate student Jordan Suchow and professor George Alvarez created these optical illusions to demonstrate how closely motion and object appearance are tied together in our vision.
This motion-induced failure to perceive changes in objects is known as silencing. Some people’s vision will simply register the object’s last perceived state before movement and lock it in place – an orange dot will remain orange in their vision, even though it has since transitioned to red or yellow. They call this freezing.
In another account of silencing, known as implicit updating, the viewer always sees the current state of the object, but remains unaware of the ongoing transition.
Why does this happen?
According to the paper Suchow and Alvarez published recently on the topic (you can read that here), our visual system must register an object’s state in order to detect changes in a moving object. If one presumes the tools needed to pull this off are local – a fixed spot on the retina to a fixed position in an image – a fast moving image might not register long enough in one spot in order for the eye to detect anything other than general movement.
The illusion serves as a lovely reminder that we can’t always trust our vision. Just because it’s right in front of our eyes doesn’t mean we’re seeing it.
Motion Silences Awareness of Visual Change [Current Biology]