Find every mask in this picture

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... More here.

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