 And from Imaginable Futures, celebrating the hard work, commitment, and achievements of the one in five college students who are parents. More at imaginablefutures.com. This is Hidden Brain. I'm Shankar Vedantam. Psychologist Ethan Cross is the author of the book, Chatter. He has studied the different roles of the voices we hear inside our heads. The harsh judge, the fearful prognosticator, the repetitive ruminator.