By far the best theory for describing the principles of our irrational decisions is something called Prospect Theory. Created in 1979 by the psychologists Daniel Kahneman and Amos Tversky, prospect theory describes how people choose between options that involve risk, like in a negotiation. The theory argues that people are drawn to sure things over probabilities, even when the probability is a better choice. That’s called the Certainty Effect. And people will take greater risks to avoid losses than to achieve gains. That’s called Loss Aversion.
