How do actors memorize all of their lines?

"A Christmas Carol" at the Guthrie, "The Grinch" at Children's Theatre Company, and "White Christmas" at Chanhassen Dinner Theatres. Whether a play with pros or a school production, it's peak time for performances. But have you ever wondered: How do actors memorize so many lines? Good Question. Susan-Elizabeth Littlefield got the answer from a neurologist who says we could strengthen our own memories by taking cues from performers.