Final answer:
The tendency to remember undone tasks until they are completed illustrates the Zeigarnik effect. This phenomenon highlights our need for cognitive closure and its impact on motivation and task management.
Step-by-step explanation:
The observation that an undone task is remembered until completed is an illustration of the Zeigarnik effect. This psychological phenomenon suggests that people remember uncompleted or interrupted tasks better than completed tasks. The tendency stems from our cognitive need for closure and resolution; unfinished tasks create a kind of cognitive dissonance that keeps them at the forefront of our memory. The importance of this effect lies in its influence on our motivation and productivity, affecting how we manage our tasks and activities.