This lead me to come up with the idea to create some tactile activities for him. I went to the dollar store and got some stones, some plastic chains, and some containers. Here's what we came up with:
The center container has uncooked rice in it. Joseph spent probably 20 minutes just manipulating and playing with the containers.
Every time he picked up the chain, he said "I like it! I like it!" Then he would say, "I like rocks!" when he was manipulating the rocks. Too cute!