Read this: The other Ancient Greek dialects, Ionic, Doric, Aeolic, and Arcadocypriot, likely had the same three-way distinction at one point, but Doric seems to have had a fricative in place of /tʰ/ in the Classical period, and the Ionic and Aeolic dialects sometimes lost aspiration (psilosis).

Which two dialects sometime gained aspiration?
What is the answer? (If it cannot be answered, return "unanswerable")
unanswerable