Piaget's theories
If you have read about child development you will probably have heard of Piaget – a Swiss psychologist who studied babies and children from the 1920s until his death in 1980.
Piaget’s theories of development are still influential today, but as techniques for testing babies’ understanding develop, some of the skills that Piaget described are being discussed.
Your baby's developing understanding of object permanence
One of these is object permanence – the idea that a young baby will believe that something no longer exists if they cannot see it, and the understanding that objects maintain their physical form as they move or if they are out of sight. If your baby is beginning to look for an object that is partially hidden, they are beginning to show that they understand that there is more of the object to see, so they have an idea in their mind of how the object looks.
They may have this understanding sooner than we think
Some researchers suggest that babies have these understandings much earlier than was first thought, and perhaps that they don’t have the memory to demonstrate this understanding until they are older. They know the object exists but just forget about it!
Either way, for you, noticing these small steps shows that your baby is beginning to understand or remember more about the world around them.
Reference:
Baillargeon, R. & DeVos, J. (1991) Object permanence in young infants: further evidence. Child development, 62(6), pp.1227-46.