One day last summer I was playing with my niece Emily in her kitchen. The bottom half of the refrigerator, right at her eye level, was covered in colorful letter and number magnets. And Emily, then 22 months, knew them all. I’d say, Where’s R?, and she’d point to R. What’s that? I’d ask and point, and she’d call out, four!

I was floored. It was a rare glimpse into what her young mind understands about the world. She can’t tell us what she’s thinking, after all.

I’ve been thinking about Emily and her magnets because of a new study about how childrens’ brains crunch numbers. Understanding what a number is — that the curved shape of the Arabic numeral 2 is named ‘two’,