People don’t talk much today about early teaching machines, some of which were made out of wood and brass. And that’s no accident, according to Audrey Watters, a longtime critical observer of edtech who is out with a new book called Teaching Machines: The History of Personalized Learning. On this episode, we’re dusting off these old teaching machines from all the way back to the 1920s, to see what these low-tech devices can teach us about education today.