Psychologists have long known that an emotion triggered in one realm—anger over an argument at home, for example—can affect how we behave in a subsequent situation, including a negotiation. Such incidental, or unrelated, emotions might influence how fully we trust someone or how much we’re willing to pay for a product. Incidental emotions can even continue to affect our decisions when we’re in a more neutral state, according to new research by professors Eduardo B. Andrade of the University of California at Berkeley and Dan Ariely of Duke University.