Albert Einstein – who many believe was on the autism spectrum himself – once said, “Imagination is more important than knowledge ...”

Most children don't have to be taught to imagine; play is as natural to them as breathing. They push a car – or a block that they imagine is a car -- along the floor and say "vrroom, vroom" as soon as they can utter a sound. They cuddle baby dolls or pretend to eat or drink from toy cups and saucers. As they play at these things and imagine, they communicate, they connect with people, and they practice life skills.

Imaginative play is typically a challenge for kids on the autism spectrum. When most kids were starting to pretend, Billy was putting together the wooden track on his train table or linking up the trains and driving them along the track. When he played with blocks, his favorite game was "dominoes," in which he lined the blocks up one after another and knocked them down.

Before we knew better, we'd try to force him to act out stories with us. We bought herds of plastic Little People, toy soldiers, Disney characters, astronauts, Thomas trains and ark-loads of plastic animals. We have two doll houses, three barns, an entire plastic amusement park, a medieval fort, a Mars rover, a space shuttle, an elaborate toy kitchen, two play houses, and yes, a Noah's ark.

The lesson we learned: You cannot buy a child's imagination. At least, not Billy's.

The second lesson we learned: We can buy Willow's imagination. She jumps on any new toy like a duck on a June bug.

Following the Floortime model of “following his joy,” we invested, instead, many hours lining up both trains and blocks. Slowly – and I mean slooooooowly – things started to change.

At first, we were able to add a few minor “playful obstructions,” little challenges that complicate the game: Something is blocking the train track; the dominoes travel over and under objects, etc.

Billy still does a good bit of echolalia, repeating lines from books and TV shows. The next development step he made in imaginative play was to act out, in small ways, lines from books or TV shows. One day, several characters had a “jumping contest.” On another, an astronaut had a race with a pig. I couldn't have been happier if he'd composed a symphony.

So this summer I've made a point to spend a certain amount of time each day “practicing” imaginative play. Scheduling it might seem to defeat the purpose of following his joy, but there's method in my madness.

In the morning, I'll listen to whatever lines he's repeating. Then while he's napping, I'll try to set up the scene of that book or TV show with his toys.

For instance, one morning, he was stuck on “Where the Wild Things Are,” understandable since we'd read that as a bedtime story the night before.

While he was napping, I rounded up the characters from the story – or the closest I could approximate in our menagerie of plastic pets – and laid them out on the dining room table. Note: I moved this activity out of his play room so that he wouldn't be distracted by other toys while we were busy with our imagining.

I found one of his Little People to be Max and a taller female doll to be the mom. I found a dinosaur, a Shrek and a couple of other “wild things” and lined them up as well. I stole the bed from the dollhouse and dug out the toilet-paper-roll-boat we'd made in craft time the day before. Then I got a plate from the toy kitchen and put a plastic chicken leg on it, because as every parent knows, the story begins and ends with Max's dinner.

Billy surveyed all this with a suspicious eye. He suspected there was a lesson in it somewhere. “No circle time,” he informed me -- “circle time” is the way he describes any particularly boring lesson-like activity.

“No circle time,” I agreed. “This is about Max going to see the Wild Things.”

His eyes lit up. “Wild things!”

So I proceeded to tell the story with the characters I had laid out. I stopped to let him fill in some of he lines. His favorites: When the mother calls Max “wild thing!” and when Max threatens, “I'll eat you up!”

When we got to the part where “a forest grew” in Max's room, I felt a bump down at my thigh. Willow was holding a small house plant. I cannot say for certain that she was suggesting we use it for the forest, but I'm so used to things coming so easily to her (see her "Jurassic BooBoo" video for a masterpiece of imaginative play), that I didn't even blink at a 15-month-old making this leap. “Good idea,” I simply told her, and added it to the scene.

After a couple of rounds of Wild Things, Billy was getting a bit bored. At the next pause in my recitation, to my surprise, he changed the story.

“We have to find Saturn!” he told me and flew Max around the table.

“Saturn?” Then I realized that he was switching to his favorite episode of Little Einsteins. “No, Billy,” I corrected him, “This is Where the Wild Things Are.”

I tried to get him to bring Max back so that he could get in the little boat and sail to the window sill where Shrek and the plastic alligator were waiting. Completely forgetting that the point was for him to imagine something NEW, I was slightly irritated that my carefully laid out world wasn't getting used.

He sighed and came back to the table. We walked Max through his paces, sailing him back home to where his dinner was waiting for him. “And ...?” I prompted Billy.

He picked up the plastic chicken leg and bonked the mother on the head with it. The doll fell over. “She's dead,” he informed me, and hopped on his scooter and pushed off. I tried not to take this plot twist too personally.

Willow picked up the Mama doll, gave her a little kiss -- “Mmwah!” -- and put her in the bed. “Seepy (sleepy),” she said, pulling up the covers. She certainly is.

I learned an important lesson: Let Billy do the reciting. If he takes one look at the Wild Things set-up and wants to act out the Little Einsteins with Shrek and the dinosaur driving the Rocket, that's great.

I've gotten a little better at play time over the weeks. We used the toy barn and animals to act out the story Click, Clack, Moo. We used his Thomas trains and Little People to pretend The Little Engine That Could. And we've acted out Noah's ark ... with Batman.

And we made a Little Einsteins “golden pyramid” out of cardboard that Billy loved as much as any store-bought toy. He immediately swam all his Finding Nemo characters in and around it.

In fact, we find ourselves in a new development stage. While not inventing completely new stories yet, Billy is mixing and matching his favorites joyfully. A cow might say, “I think I can, I think I can” and a train might travel to the land of the Wild Things. Batman moves in an out of diverse roles with the ease of a plastic Lawrence Olivier.

On Monday we're going to make totem poles out of cardboard tubes, inspired by another favorite Einsteins episode. I wonder what Batman will make of those...