These books further stimulate language development, as well as concepts such as "all gone" and "more." Skills enhanced at this stage include the capacity to predict, object permanence and one-to-one correspondence. More advanced lift-the-flap books for this group allow babies to demonstrate what they can accomplish and the text and pictures encourage them to perform different actions.Even babies too young to count can recognise the difference between one thing and two things. And that understanding sets the stage for number recognition. Vivid illustrations show one ball and two balls, one duck and two ducks, one spoon and two spoons. By following these illustrations and repeating both numbers, babies will begin to recognise quantities and become comfortable with numerical symbols.