Riley asserts that some findings of cognitive science conflict with key principles of personalized learning--that students should control the content of their learning and that they should control the pace of their learning. A personalized approach is in conflict with the cognitive science principle that committing key facts in a discipline to long-term memory helps a person perform in that discipline (because resources for working memory and thinking are freed up). Unless students have stored important facts in long-term memory, they haven't learned them in a usable way--and if they learn only the content they choose, Riley argues, students aren't likely to make the sustained effort needed to do so. Letting students choose their pace also runs afoul of cognitive science because the thinking needed for learning is so fatiguing that students need "the equivalent of a trainer in the gym" to help them keep on pace. The third principal of personalized learning, using technology, however, fits well with cognitive science and shows promise for empowering teachers to boost subject matter learning. Instead of focusing on personalization, we should train teachers to make scientifically informed decisions on instruction and technology--empowering them as "scientific professionals."