Pollan begins his exploration of caffeine by admitting that by cutting this psychoactive drug out of his daily routine he experienced symptoms of withdrawal that left him feeling particularly demotivated and purposeless. The author claims that around 90% of all people in the world use caffeine regularly, making it the most common psychoactive drug globally (92). As such, Pollan feels it is necessary to give up his daily caffeine habit completely to understand its effect on the human brain and society itself. However, this experiment is not without consequences, as Pollan notes that caffeine withdrawal can include symptoms such as “headache, fatigue, lethargy, difficulty concentrating, decreased motivation, irritability, intense distress, loss of confidence(!), and dysphoria” (93) and shares that he experienced each of these. Pollan procrastinates about cutting out caffeine until finally he begins his experiment by replacing caffeinated coffee with mint tea, which fails to clear his mental fog. Over the course of his first week Pollan feels less mentally sharp, and his writing work feel overwhelming, which makes him realize the role caffeine was playing in enhancing his concentration and improving his mood.

Pollan examines two plants responsible for producing caffeine: Coffea, or the coffee plant, and Camellia sinensis, or tea.