tickle hands

Every time I would open the refrigerator with Jacob present, he would reach in and "ticka, ticka, ticka" the side of the almond milk carton. As it was the right side of the carton (facing in towards the fridge) I could really see what he was tickling and thought it was kind of strange. Then I turned the carton around and saw these hands. I'm not sure what draws him to tickling them. But he does it. every. time.