In one of the book's most controversial chapters, Ariely explores how emotional states alter our moral compass. He asked participants to predict how they would behave when sexually aroused. When in a "cold," rational state, they predicted they would behave ethically. However, when they were actually aroused, their propensity to engage in unsafe sex or morally questionable acts skyrocketed. We drastically underestimate how different we are under the influence of emotion.

: Choosing a free item often causes us to miss out on a better deal that costs a small amount.

Even years after its release, Predictably Irrational remains relevant because human nature doesn't change. Whether you are a trying to understand consumer behavior, a manager trying to motivate a team, or simply someone trying to save money , Ariely provides the "cheat codes" to human psychology.