In educational circles, children are allowed to "feed" the puppets magnet letters they name correctly, or color blocks etc.... the giggle of feeding them is enough to make the child forget they're doing something challenging!
Not only did U.S. educators play a leading role in designing and carrying out the study, but the results, which showed U.S. high school students lagging behind those in other industrial countries, attracted widespread attention in the news media and ineducationalcircles.
Despite decades of research on students and teachers, the concept is still highly controversial within educationalcircles, and it's almost completely unproven in workplace settings.