Sword Specialization is a passive human racial ability. It grants an expertise bonus while using swords. When dual wielding different types of weapons, Sword Specialization is applied to each weapon individually, so that if you dual wield a sword and an axe, only attacks made with the sword benefit from Sword Specialization. When dual wielding two swords, all of your attacks will benefit from Sword Specialization. For attacks that only use the mainhand weapon, such as a rogue's Sinister Strike, only your mainhand expertise matters.