Complex sentence: Prior to Genie's case there had been some observations of right-hemisphere language acquisition in adult split-brain and left hemispherectomy patients, which had consistently shown that both populations were much better at learning vocabulary, although they were able to learn some basic grammar.
Split into simpler sentences: Prior to Genie's case, there had been some observations of right-hemisphere language acquisition in adult split-brain and left hemispherectomy patients. These studies had consistently shown that both populations were much better at learning vocabulary, although they were able to learn some basic grammar.