The Zeigarnik Effect was discovered in 1927 by psychologist Bluma Zeigarnik. It states that once a task has begun it creates a task-specific tension which is relieved once the task has been completed. So the open orders are more easily remembered by waiters because the bill has yet to be closed but, as soon as the bill is paid, there is no reason for the waiter to remember the order and soon forgets.
The Zeigarnik Effect is also present in sports. Basketball player James Harden had a tendency to make a rushed shot whenever contact was initiated by a defender. This would lead to a foul and a stoppage in play. The tension experienced by the viewer at the stoppage in play is effectively the same as an “open” bill experienced by the waiter and the incident stood out in the mind of many fans. The NBA listened to criticisms of Harden and created the “Harden Rule” which changed the requirements of what constitutes a shot.
