Concept of Perceptual Contrast
The concept of perceptual contrast points out that we evaluate the information based on information that we already have. For example, if you borrow a friend's car and accidently scratch it, your friend will most likely be less angry if you present it to your friend like, "Oh my gosh, you are going to kill me. There was an accident and your car is totally beaten up. I'm so sorry." rather than, "Oh my gosh, you are going to kill me. I scratched your car while running errands."
There is a difference between a 'not scratched' state to a 'scratched' state AND a 'totaled' state to a 'scratched' state. By stating that the car is totaled you are providing the comparison that your friend will use to perceive how damaged the car is.
So...present an example of perceptual contrast from your own experience. Be sure to explain whether you used it or whether it was used on you.
BTW - Perceptual Contrast is a type of Anchoring judgment