What is the rhetorical purpose of the four boldface section headings that Winn uses to divide her essay in The Plug-In Drug by Marie Winn?

The boldface section headings in "The Plug-In Drug" by Marie Winn serve to clearly outline and separate different key arguments and perspectives discussed in the essay. They help guide readers through the text and emphasize the main themes being presented in each section. Additionally, they provide a visual aid for readers to navigate through the complex ideas presented in the essay.