You may have missed this part of the article near the beginning:
“Just one problem: I don’t have a child, so I needed to borrow one. Fortunately, my editor gleefully volunteered her 14-year-old, Sophie, to be a test subject.”
“Just one problem: I don’t have a child, so I needed to borrow one. Fortunately, my editor gleefully volunteered her 14-year-old, Sophie, to be a test subject.”