Having trouble finding all 24 face coverings? There’s a reason tasks like this are challenging for even experienced puzzle sleuths: We don’t see everything in our field of view. In fact, our brains forbid it.

Our minds can only focus on so much at once, says Susana Martinez-Conde, a neuroscientist at SUNY Downstate Medical Center in New York. Neurons in our visual cortices have limited bandwidth. If they attempted to take in everything, we would struggle to pick out life-or-death details. So the brain directs our vision, filtering out irrelevant objects. If we’re crossing the street, it sends signals to tune into a car speeding toward us as opposed to, say, a bluebird or a friendly neighbor out for a stroll. We might miss some things, but at least we’ll live to tell the tale.

To crack the puzzle above, focus your attention on one small section at a time—otherwise your noggin will lock in on the biggest parts of the picture and blur out everything else.

Click here to see the answers!

This story appears in the Fall 2020, Mysteries issue of Popular Science.