How does the economy react to the arrival of a new major technology? The existing literature on General Purpose Technologies (GPTs) has studied the role that mechanisms like secondary innovations, diffusion, and learning by firms play in the adjustment process. By contrast, we focus on a new mechanisms based on the interplay between technological change and human capital accumulation. We show that technological change that requires more education and training, like computerization, necessarily produces an initial slowdown. Surprisingly, however, technological change that lowers the training requirement, like the move from the artisan shop to the factory, can produce either a bust or a boom. We identify three key properties that determine which effect will occur: (1) the productivity of inexperienced workers; (2) the speed with which experience increases productivity; and (3) the level of general skills required to operate the new technology.