Chapter 6 page 14

Susan looks down silently. The Director sets down her cup and stands. She walks to the window, hands folded behind her back. Growth charts run in the background, comparing a child silhouette to the taller silhouette of a teenager or young adult who strikes a confused pose.
Director: Every generation is a little different.
In terms of cognition, we’re looking at approximately four to nine years, relative to the development of an average human child. 
Susan: But even that’s hard to say. It’s like saying one dog year is equal to seven human years. We’re not mapping simple equivalents. Some concepts and skills are grasped more quickly, while others—
Director: Right, right.