Reviewed by: Teaching Machines: The History of Personalized Learning by Audrey Watters Victoria Cain (bio) Teaching Machines: The History of Personalized Learning By Audrey Watters. Cambridge, MA: MIT Press, 2021. Pp. 328. Prior to the widespread exhaustion with online learning prompted by the pandemic, educational technology media coverage in the United States was a lesson in breathless excess. Blogs, trade journals, and national news platforms detailed how digital tools were "disrupting," "revolutionizing," and "transforming" American schools. Most of these articles lacked any historical context, or relegated it to illustrated sidebars featuring slates, film projectors, and other bygone classroom tools. In a lively new book, independent scholar Audrey Watters reminds us that nothing is new under the ed-tech sun. Watters's Teaching Machines uses the history of B. F. Skinner's teaching machine to explore the broader psychological, pedagogical, and economic history of programmed learning. Teaching Machines chronicles how Skinner's crude machine, designed to provide immediate feedback and allow students to work at their own pace, piqued the interest of psychologists and reporters and became the blueprint for future technologies. Watters makes clear that techno-optimism, efforts to use technology for social engineering, and the drive to prioritize financial profit over pedagogical value feature as prominently in the lifespan of earlier teaching machines as they do in educational technology today. While ed-tech entrepreneurs trumpet "personalized learning" as a brand-new idea, Teaching Machines makes clear that educators and engineers have been attempting to enable students to learn on their own since the 1920s. Teaching machines established many of the norms for digital technologies, breaking lessons down into small chunks of content, providing users with immediate results, and allowing students to move at their own speed. Mechanical education didn't have to be mechanistic, argued prewar developers of these machines, and automation and individualization [End Page 853] would go hand in hand. Instead, Watters argues, teaching and testing came to resemble one another, and by the 1960s such machines were eventually denounced as dehumanizing exercises in behaviorism. The last few years have seen something of a boom in histories of educational technology, as scholars like Katie Day Good, Morgan Ames, Joy Lisi Rankin, and Justin Reich have focused on the emergence (and often failure) of classroom tools and practices. Watters's most important contribution to this literature is to reframe corporations' role in the creation and dissemination of new technologies. She demonstrates how firms stonewalled education-oriented inventors and refused to invest in their products, preferring instead to repurpose existing technologies. The result, she argues, was a deeply conservative take on teaching and learning. Successive chapters detail these dynamics, describing Sidney Pressey's struggles to find a company that would bring his teaching machine to market in the 1920s, IBM's slow-walking purchase of Reynold Johnson's test-scoring "Markograph" in the 1930s, and Rheem Manufacturing's failures to produce a classroom-ready version of Skinner's machines in the 1950s. While historians have tended to focus on corporate enthusiasm for educational technology, Watters makes a convincing case that corporate resistance was equally important to consider. Taken together, her case studies offer a damning indictment of corporate capitalism's historical impact on classroom technologies. Historians of technology will find Watters's book illuminating, but she's not just speaking to scholars; rather, this book takes square aim at Silicon Valley. She delights in using archival research to puncture what she calls the "ed-tech imaginary," explaining how historical narratives peddled by tech entrepreneurs are lazy, inaccurate, and self-serving, and she concludes the book with warnings about technologies of behavioral control. Intended as a trade book, Teaching Machines is packed with entertaining details and detours. Readers learn about Pressey's excessive fondness for exclamation points, Eunice Shriver's personal interest in Skinner's Baby Box, and the career of Susan Meyer Markle, whose work writing programs for teaching machines was minimized by her male peers to the point that she became invisible in a field she had helped to found. In places, the book would benefit from more historical analysis and context, to help readers understand which of these details was most important. Her narrative also raises, but...