Some skills may fit within more than one field. For example, Elvish might be learned as a skill under Language Science, or as a skill under Elvish Culture. In some cases, the usefulness of a skill will vary depending on which field the character has it with.
It is up to the player to choose which field they learn their normal skills under, even their automatic ones such as their native tongue. For example, if a player wants their character to be a linguist, they will likely get the Language Science field for their character. If they wish, they can place their native tongue under Language Science rather than under Native Culture. This will give them their Language Science field bonus with their native tongue; it will also help them read their native tongue if they add literacy to their Language Science field.
Such a choice will, however, affect the usefulness and character of the skill. In the example above, the linguist will likely be more precise in their use of their native tongue. Their fellow speakers may find them a bit pedantic; they may miss out on some of the cultural implications of the language, such as slang.
A player can move an automatic skill out of native culture any time they acquire a field that the skill could fit under.