Moses 6

Upon receiving commandments and revelations from the Lord we learn that -

"...a book of remembrance was kept, in the which was recorded, in the language of Adam, for it was given unto as many as called upon God to write by the spirit of inspiration..."  (Pearl of Great Price | Moses 6:5)

And it was these writings by Adam and his righteous posterity, even prophets of God, that -

"...their children were taught to read and write, having a language which was pure and undefiled."  (Pearl of Great Price | Moses 6:6)

Obviously, then Adam and Eve were not only intelligent but must have been educated being taught a language that was pure and undefiled.  But not only knowing and understanding that language, they also must have been taught to read and write this language.

As we read the words of Enoch, we receive great incite on the matter as he taught the plan of salvation to the people in his day explaining -

"For a book of remembrance we have written among us, according to the pattern given by the finger of God; and it is given in our own language."  (Pearl of Great Price | Moses 6:46)

It seems to me that not only were Adam and Eve taught the "Adamic" language which we are told is pure and undefiled, they were taught how to read and write by the Lord "according the the pattern" as taught them from the Lord.

Being that the languages were altered in the days of Babel, we would have to assume that the Jared and his brother must have initially had this pure and undefiled language in their day as we learn that the Lord -

"...did not confound the language of Jared; and Jared and his brother were not confounded."  (Book of Mormon | Ether 1:35)