Yesterday, Cognitive Daily posted a fairly compelling visual illusion. There is a while disk and a black disk. In the middle of each disk is a circle. The two circles go from black to white back to black in sequence.
Normally, the rules of perceptual grouping would cause you to see the two smaller disks blinking in unison as being related. However, in this case, due to the smaller disks being inside larger disks, most people see the disks blinking out of sequence. That is, you interpret the scene as a hole appearing in the left disk, then in the right disk, then in the left disk.
Both interpretations are correct. It’s a matter of what your visual system focuses on. What interests me is, looking at the comments on this post, is that while the vast majority see the alternating blinking, some people only see the disks blinking in unison. One possibility is that they are misunderstanding what they were supposed to see. If there is some small percentage of people whose visual systems focus on different grouping principles, that could be very interesting and be useful in understanding perceptual grouping in the visual system.
So, if you only see the inner disks blinking in unison and don’t get the alternation illusion, comment here or send an email to coglanglab_at_gmail.com.
Try out the illusion here.