Brian Jeffrey Fogg, who goes by BJ Fogg, is a professor of sociology at Stanford University, where he heads the Behavior Design Lab. In 2007, he taught a class on how to create Facebook apps using persuasive techniques; the apps garnered 24 million views. Fogg also heads the Tiny Habits Academy. He lives in Northern California and Hawaii with his partner, Denny; he enjoys surfing and does so up to 100 times a year.

Linda is the author’s older sister; they’ve been close since childhood. Linda has faced many struggles, including bankruptcy, a husband with early-onset Alzheimer’s, and a son who died of an overdose. As his training program grew from free to huge, the author asked Linda to help him develop a system of trainers and programs to handle the flood of interest. Her work with Tiny Habits benefitted her, and she developed a flair for teaching its principles. Her story is one of several mentioned in the book that demonstrate how Tiny Habits can make surprisingly powerful improvements in lives haunted by daunting challenges.