Leo is 4 years old. When playing with his toys, he insists that his toy dinosaur is feeling sad and needs to be wrapped in a blanket. Later, when his father pours his juice from a short, wide plastic cup into a tall, narrow glass, Leo is delighted because he believes he now has more juice.

Maya is 9 years old. She understands that pouring the juice into a different glass does not change the amount. However, when her teacher presents her with a hypothetical problem: 'If feather-touching can break glass, and Dawn taps a window with a feather, what happens to the window?', Maya insists, 'Nothing happens, because a feather is soft!'

Discuss Piaget's theory of cognitive development. Refer to Leo and Maya in your answer.