Baby Cooper dropped his spoon off of his high chair, and it made a clattering sound that he liked. When his mom picks it up and gives it back to him, he drops it again but harder this time to see what it will sound like. When his mom gives it back to him a third time, he decides to throw it to see if that changes the sound it makes. This type of experimentation is most common in which of Piaget’s stages of sensorimotor intelligence?