Zeigarnik effect called after a Russian psychologist, Bluma Zeigarnik (above photo), who noticed an odd thing while sitting in a restaurant in Vienna. The waiters seemed only to remember orders which were in the process of being served. When completed, the orders evaporated from their memory.

Zeigarnik went back to the lab to test out a theory about what was going on. She asked participants to do twenty or so simple little tasks in the lab, like solving puzzles and stringing beads...