Frederick II, Holy Roman Emperor (called Stupor Mundi, ‘Wonder of the World’, and not to be confused with Frederick I, Barbarossa), reigned from 1220 A.D. to 1250 A.D., and was, apparently, of a scientific bent. His experiments were recorded by a monk, Salimbene di Adam, who met Frederick and whose admiration for the Emperor was moderated heavily by the fact that he considered him a heretic. One of the experiments concerned natural language. Frederick wanted to know what man’s original language was, the language imparted to man in the Garden, the language of man before Babel. Accordingly, he took several infants and put them alone in rooms, making sure that they would be adequately fed, clothed, cleaned, and warmed. However, so that their language development might remain pristine, he bade the
“foster-mothers and nurses to suckle and wash the children, but in no ways to prattle or speak with them; for he would have learnt whether they would speak the Hebrew language (which had been the first), or Greek, or Latin, or Arabic, or perchance the tongue of their parents of whom they had been born. But he labored in vain, for the children could not live without clappings of the hands, and gestures, and gladness of countenance, and blandishments.”
Without nurturing and affection, the children all withered and died.
The quotation can be found several places, most easily Wikipedia.