Introduction

Suppose you are given the following list of items to remember:

1. Cat
2. Dog
3. Horse
4. Airplane
5. Cow
6. Sheep
7. Chicken

Which do you think you would remember the best? The odds are ‘airplane’ would be recalled by almost everyone because it stands out among the animals in the rest of the list. Now suppose you were shown this list:

1. Airplane
2. Car
3. Motorcycle
4. Horse
5. Bus
6. Tractor
7. Truck
8. Boat

In this case, most participants would remember ‘horse’ because it stands out among the list of vehicles. Airplane doesn’t stand out anymore, does it?

The phenomenon of remembering unique items in a set with better accuracy was first described by Hedwig von Restorff in 1933. It is often referred to as ‘the von Restorff effect’ or the ‘isolation effect’.