Imagine you are about to watch a car ad. You now have expectations about various aspects of the car, including its reliability, comfort, acceleration, cool factor, and so on. These all combine into your total estimate of how much the car would be worth to you. After you watch the ad, your expectations about many aspects may change. You may think it more cool and reliable, but less comfortable and slower. Sometimes you will think the car is worth more, and some times less, than you thought before.