Simple

Completely out of the blue, Isabella rolls up on me while I was cooking dinner.

"Mom, did you know that boys and girls have different types of humors?"
"Really?"
"It's true. Girls' humor is complicated and based mostly on memories. Boys... well boys have something called simple humor."
"You're absolutley right, dear. Do you know what else? They never grow out of that."
"I know. Sad."