 Bellugi told Schaller that she had strong reservations whether Ildefonso could learn language at his present age (because according to the Critical Period Hypothesis language is only properly mastered in youth).Bellugi also noted that none of her students in tests of language acquisition had yet reached puberty, and that she could find no documented cases of an adult learning a first language.Schaller chose to move forward with teaching Ildefonso, as his dedication inspired her.