Fallout traits

Traits in the original Fallout are optional character modifications that affect the player character. Traits modify different aspects of gameplay, including (but not limited to): Primary statistics, derived statistics and skills. Traits always have both positive and negative results.

One can choose up to two traits when designing a character (or none at all). Choosing the Mutate! perk lets the player change one of his traits. Note that if you chose no trait at character creation, you cannot fill the empty slot with this perk.