At the age of four, Bela began to form memories, marking a significant stage in her cognitive development. She started using the word "yesterday," though her understanding of it was flexible, as she associated it with anything that was not present in her current experience. This reflects the innocence and fluidity of a child's interpretation of time and memory.

The concept of the past, for Bela, was not linear but rather a collection of moments all packed into the single term she grasped. This illustrates how children perceive time and memory in a more abstract way, where past experiences lose their chronological order and become a single entity defined by something as simple as a word.