The psychologist Barry Schwartz used the kindergarten experiment to excoriate an experimental New York schools programme which paid older children to show up and work hard.

Mr Duncan is, in fact, making early education one of his priorities, by including it in the next round of funding for Race to the Top, the big federal programme for schools.

Some one and a half million children in more than 4, 000 British schools are now involved in the Bloodhound Education Programme.