I heard Middle Son giggling in the living room. I also heard Willow, his service dog, running back and forth. So I went to investigate.
I found that Willow had dropped her kong on the couch next to Middle Son, and was jumping up and down, as if to coax him to throw it. Middle Son looked interested, but didn't seem to grasp Willow's desire. He was watching her and giggling, while still trying to keep his hands away from her.
I picked up the kong and handed it to him. I pointed down the hall and told him to throw it. He did. Willow scrambled after it. Middle Son laughed. With prompting, he threw the toy for her half-dozen or so times. That's the longest I've ever seen him play with her. It was wonderful to see.