This optical illusion occurs because of a process called binocular rivalry. You probably don't realize it, but your eyes sometimes vie for "dominance." If there are different, competing images seen by each eye that can't be easily combined, one image will end up suppressed by your brain. In this case, that suppression makes it look like your hand has been through a giant hole-punch!
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Key Facts In This Video
Ambiguous figures are optical illusions that cause you to switch between multiple ways of viewing an object. 00:22
When your brain can't combine different images seen by each eye, it will suppress the image seen by one eye and favor the other. 01:32
You don't typically notice the dominance and suppression that occurs in your vision because your eyes rarely stay fixed on one thing for more than a few hundred milliseconds. 02:27