There are several times in the first act of The Miracle Worker when Helen shows her natural intelligence level. One time occurs when Helen is playing with her doll. She feels her doll's head, but finds no facial features on it. Helen is distraught because she knows that her doll should have facial features and eyes. She proceeds to touch the faces of everyone in the room, specifically their eyes. Helen tears two buttons off her aunt's dress and attempts to put them on her doll's face. Her mother raises Helen's hand to her own eyes to inquire about what Helen is trying to do. Helen nods, showing her mother that she is indeed attempting to add eyes to the face of her doll.
Later when Annie Sullivan arrives, Helen gets angry with her and locks the teacher in her room. Then she takes the key and hides it. Annie later finds it in Helen's mouth before the girl drops it into the well.