Their experiment wasn't sophisticated. They removed all the dolls and flannel bears and wooden trucks from the nursery, and observed how the children amused themselves with only chairs, a table and some blankets. Amazingly, they did fine, converting the furniture into shelters.
Now, you may be thinking there's something chilly about all this. Neither Rainer nor Elke (nor, to be honest, the Friedrich Engels Bogen nursery) sounds like a barrel of laughs. You can almost picture the pair, a white- coated Mulder and Scully, as they performed this exercise in deprivation on the hapless tots of Munich, packing up the Mousehole games, hurling Barbie dolls and Sylvanian woodland creatures into Sainsbury's bin-liners and consigning Mr Bucket and the Junior Meccano set to the darkest cupboards. "Zo," they must have assured each other at the end. "Zer kinder no need for zer playzings gehaften. Not Bob zer Builder, nor zer Crocodile Dentist, not even zer Foolish Putty..."
If true, this could save us all a fortune. In Britain we spend pounds 850m on toys in the run-up to Christmas. Imagine what we'd save if children were found to thrive without small plastic homunculi and cuddly elephants.
I resolved to try a controlled experiment in the home environment. I piled the playroom toys into a cupboard, swept the house clean of Lego bits, jigsaw pieces, Scalextrix track and Teletubbies cups and saucers. "It won't work, you know," said my 12-year-old dryly. "She'll just have hysterics."
But I wasn't so sure. These Germans know a thing or two.
My youngest child came into the kitchen looking for her Play Cafe, with its cash register and plastic vegetable rack.
"I've got rid of it because you don't actually need toys, darling," I explained.
"But I want to wash the potatoes in my sink," she said. "I always wash the potatoes in my sink."
"You can pretend to wash them, sweetheart," I told her. "It's the same thing. It's all to do with pretence and imagination".
"I WANT TO WASH THE..." Though only four, she has a uniquely carrying voice. "Look," I said, "here's a real potato. You can pretend to wash it in this, er, sink."
"But that's not playing, Daddy," she said, and began to sob.
"Dad," said the middle child, aged eight, "where's the Wheels From Hell Blitz Machine gone?"
"I threw it out because you don't really need toys," I reassured him. "You will become more socially integrated and better adjusted, group- dynamics-wise, if you cease to indulge this solipsistic absorption with a remote-controlled motor vehicle."
An eloquent statement of the case, I felt. Unfortunately, he stamped off in the middle of it and started to scream in the hallway.
The youngest reappeared, holding a King Edward potato. "This is my baby," she said. "He's called Pinkie..."
"Lovely, darling," I beamed. So Rainer and Elke had been right all along. "You see?" I said. "You don't need toys at all."
"...and I'm taking him upstairs to meet Baby Expressions, who's his mummy."
"I've in fact put Baby Expressions in the attic, darling," I told her, "because you can indulge in quasi-maternal, role-playing scenarios without relying on expensive and stereotypical petit-bourgeois simulacra."
She threw the potato at me. I still have the bruise. Some children just have no imagination.