Piaget's concept of object permanence is essential to understand.  But how did they study this idea among 1 year olds?  Obviously children can't tell you that they believe that something no longer exists when they can't see it, so how do we know what is going on inside a child's mind?  How about this challenge: do animals also understand object permanence?  If you've ever seen your cat or dog look under or around objects for a lost toy then yes - you've seen that they do understand object permanence.How can you study object permanence - or a related idea called "expectancy violation" - in animals?  Let's take a look in this 150 episode of The Psych Files.