After she calms Betty Parris and amazes the room, Rebecca Nurse establishes her credibility by referencing her vast experience when it comes to children and their strange behaviors.  She's had eleven children and twenty six grandchildren, and "[she] has seen them all through their silly seasons, and when it come on them they will run the Devil bowlegged keeping up with their mischief."  Thus, she has witnessed a great many children growing up, and she understands that acting oddly and making questionable decisions is simply a part of this process.  She implies that children do things for strange reasons, but that this is a common, indeed a natural, part of life.  It is not, as some suggest in the play, unnatural.  She is very much the voice of reason, wise and understanding, when all around her are the beginnings of hysteria and chaos and superstition.