Chapter 1 of Louis Lowry's Number the Stars is titled, "Why are you running?" It introduces the characters and the way they interact with a very challenging environment: Nazi-occupied Copenhagen, Denmark.

Kristi is a very young girl. She is five years-old, and Annemarie's little sister. She has lived her entire life under the circumstances we learn about in the novel, so she cannot tell any difference between life before and after the occupation.

By all accounts, Kristi is an example of innocent bliss. She is too young to see what surrounds her, and her life experience has given her no reason to fear anything. Everything she knows about the world that surrounds her is that the soldiers are a part of it:

Kirsti had been—well, nothing more than a silly little girl, angered because the soldier had touched her hair that afternoon. She had known nothing of danger, and the soldier had been amused by her

Surely, in the eyes of the soldiers, Kristi was just another amusing little kid; a play-thing that posed no danger or threat to anyone. Therefore, the relationship between the soldiers and Kristi could arguably be described as one of social determinism: the soldiers felt no threat from Kristi, mainly due to her young age, so they treated her like the little girl that she was. Similarly, Kristi felt comfortable around the soldiers because they treated her the way everyone else did, so she responded with the innocence and joy that was expected of her.

Imagine how different it would have been if Kristi's parents had groomed her to fear the soldiers. She would have acted strangely around them, thus rising questions as to whether the family was hiding something. Luckily for her, her parents just allowed her to be the five-year-old she was meant to be, and this ended up working in everyone's favor.