Heartless

Heartless is a special perk in the Fallout: New Vegas add-on Old World Blues.

Obtaining
In the initial dialogue with Dr. Klein as part of the quest Welcome to the Big Empty, you find out that your brain, heart, and spine have been removed and replaced. This perk represents the replacement of your heart. While you technically have these perks from the start of the add-on, they are unlocked in the course of the conversation.

Effects
You cannot be poisoned, you gain +25% bonus to healing items and robots have -50% critical chance against you.