I don’t remember exactly when I learned the concept of infinity, but at some point in childhood I was using it as a trump card in arguments with my sister. We’d volley along the lines of:

“I have seven beads!”

“Well, I have twelve beads!”

“I have infinity beads!”

(Drops mic.)

Infinity seems like an abstract mathematical concept, and I suppose it is. But one application of infinity is integral to many aspects of everyday human cognition, including language, music, and problem solving. It’s called recursion, and children begin to grasp it around age 9, according to a fascinating study published in the October issue of Cognition. What’s more, a child’s understanding of recursion in pictures is tightly linked to her understanding of grammar.

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