As lawyer Mark Lanier flashed a cartoon road sign reading “Science of Addiction ” on a large screen inside a Los Angeles courtroom on Tuesday, Dr. Anna Lembke walked jurors through what she described as the four “C’s” of addiction: loss of control, cravings, compulsions, and consequences. Called as the first witness in a closely watched trial over claims Meta and YouTube negligently designed platforms that were addictive to children , Lembke, the medical director of Stanford University’s