I came to the realization that Liam excels in being silly and clowning around. For a 17 month old he has a fairly well developed sense of humor - particularly slap-stick. He will wear baskets on his head (like this photo from a few days ago). Or put shoes on his hands - which he did today with Scarlet's shoes when she was visiting us. This evening, the end of a particularly long day...he grabbed his daddy's slippers, put them on, and walked around to see our reaction (laughter of course!).
So while Liam may not be any quicker at learning words that average, and is only slightly above average in the mobility category, he excels in humor! And that's just the sort of little boy I need. :)