Stare at 100 dots for 30 seconds, and your brain starts lying about how many things it sees

Gilisa, CC BY-SA 3.0, via Wikimedia Commons

Stare at two clusters of dots for 30 seconds. Then look at two identical groups of dots side by side. The group on the side you were staring at will look like it has fewer dots — even though both groups are exactly the same size. Your brain just recalibrated its number sense, and it did it without asking.

This i…