What Catholic theology actually is, is a nice question. But there is no doubt what Augustine says. He argues here (in a polemic against Pelagius) that Adam was created with the intellectual faculties of an adult. After the Fall, by contrast, humans are created in a ‘cloud of ignorance’, i.e. the baby state. This cloud of ignorance lasts far longer than any cloud of drunkenness. If this ignorance is contracted as soon as we are born, “where, when, how, have they by the perpetration of some great iniquity become suddenly implicated in such darkness”, he asks. A new-born child is already guilty of offence.
Seeing now that the soul of an infant fresh from its mother's womb is still the soul of a human being—nay, the soul of a rational creature—not only untaught, but even incapable of instruction, I ask why, or when, or whence, it was plunged into that thick darkness of ignorance in which it lies? If it is man's nature thus to begin, and that nature is not already corrupt, then why was not Adam created thus? Why was he capable of receiving a commandment? And able to give names to his wife, and to all the animal creation? For of her he said, She shall be called Woman; Genesis 2:23 and in respect of the rest we read: Whatsoever Adam called every living creature, that was the name thereof. Genesis 2:19 Whereas this one, although he is ignorant where he is, what he is, by whom created, of what parents born, is already guilty of offense, incapable as yet of receiving a commandment, and so completely involved and overwhelmed in a thick cloud of ignorance, that he cannot be aroused out of his sleep, so as to recognize even these facts; but a time must be patiently awaited, until he can shake off this strange intoxication, as it were, (not indeed in a single night, as even the heaviest drunkenness usually can be, but) little by little, through many months, and even years; and until this be accomplished, we have to bear in little children so many things which we punish in older persons, that we cannot enumerate them. Now, as touching this enormous evil of ignorance and weakness, if in this present life infants have contracted it as soon as they were born, where, when, how, have they by the perpetration of some great iniquity become suddenly implicated in such darkness? On Merit and the Forgiveness of Sins, and the Baptism of Infants Book I, Chapter 67 On the Ignorance of Infants, and Whence It Arises.