The third house answers the question: what do you think? The third house represents basic education, learning, communication, and siblings.
A person with Saturn in the 3rd likes to plan things out. Neptune in the 3rd house can indicate scattered communication. Venus in the 3rd can mean a person good at learning languages.
Astrologer Robert Hand says, "The third house is a level of mind that most of the time operates unconsciously, but it can be made conscious whenever you choose. It is unconscious not because you can't look at it, but because you normally do not choose to."