In a phenomena Spivack refers to as "winning the baby lottery", infants will get too excited to fall asleep for their second nap because they are so pumped to keep practicing the brand-new developmental milestone that they've just learned (kind of like how an adult who won the lottery wouldn't be able to sleep from excitement). But don't be fooled. "If your child is around the 12-month-old mark and it's aligning with the beginning of the walking stage, that can lead to a temporary dropping of a nap until the excitement over walking calms down," Spivack explained. So you might still be able to tempt them down for a second nap once the newness wears off.