"When kids write letters, they're just messy," she says. As kids practice writing "A," each iteration is different, and that variability helps solidify their conceptual understanding of the letter.

A slew of recent brain imaging research suggests handwriting's power stems from the relative complexity of the process and how it forces different brain systems to work together to reproduce the shapes of letters in our heads onto the page.

In adults, taking notes by hand during a lecture, instead of typing, can lead to better conceptual understanding of material.

Why writing by hand beats typing for thinking and learning