In an experiment, two-year-old boys and their fathers made pie dough together using rolling pins and other utensils  Each father-son pair used a rolling pin that was distinctively different from those used by the other father-son pairs, and each father repeated the phrase rolling pineach time his son used it
But when the children were asked to identify all of the rolling pins among a group of kitchen utensils that included several rolling pins, each child picked only the one that he had used
No two children understood the name rolling pinto apply to the same object.