Bluma Zeigarnik was a Lithuanian psychologist who once observed that waiters had better recollection of unpaid bills orders than orders for which bills were paid. Once the unpaid bills were paid their recollection about those orders went down.
Bluma studied this phenomenon in more details and come up with what known as Zeigarnik effect.
Zeigarnik effect states that people remember uncompleted or interrupted tasks better than completed tasks.
This effect can be of help if someone is prone to procrastination. The idea is if you are procrastinating, just initiate task by taking first few steps, the Zeigarnik effect will remind you about the incomplete task and you will then take few more steps and so on till momentum builds up and task is complete. If you fail to take initial few steps, chances are you will simply forget about it and remember it only when deadline approaches or someone reminds you.
Zeigarnik effect is also used by producers of TV serials, when they don’t show complete episode and remind you to watch it next week. The curiosity to know what will happen brings in the stickiness factor and TV serial is able to get loyal viewership.
This effect was also used in case of Arabian nights. Prince Shahryar had a queen who was not faithful to him, so the sadistic prince decided to take revenge on all women in kingdom. He used to marry a woman daily and next day used to execute her. Finally to save women, daughter of Vizier called Scheherazade, decided to marry Shahryar. Night before execution she told prince a story, but by morning she could not complete it, since prince was curious to know the end of story, he decided to postpone execution by a day. Scheherazade used Zeigarnik effect daily and managed to postpone her execution 1001 times! It is said that after 1001 days the prince decided to spare her life.