"For me, as a beginning novelist, all other living writers form a control group for whom the world is a placebo"

This quote by Nicholson Baker suggests that as a starting novelist, he is seeking to other living authors as a source of motivation and assistance. He is using them as a control group to measure his own progress and development as a writer. He is suggesting that the world is a placebo, or a dummy drug, for these writers, and that he can utilize their work to compare and contrast his own. He is likewise suggesting that the world is a placebo for him too, which he can utilize the work of other authors to assist him establish his own composing style and technique. By seeking to other authors as a control group, he has the ability to measure his own progress and development as a writer.