“As with all desirable difficulties, the trouble is that a head start comes fast, but deep learning is slow. “The slowest growth,” the researchers wrote, occurs “for the most complex skills.” Duncan landed on the Today show discussing his team’s findings. The counteropinion was supplied by parents and an early childhood teacher who were confident that they could see a child’s progress. That is not in dispute. The question is how well they can judge the impact on future learning, and the evidence says that, like the Air Force cadets, the answer is not very well.* Before-our-eyes progress reinforces our instinct to do more of the same, but just like the case of the typhoid doctor, the feedback teaches the wrong lesson. Learning deeply means learning slowly. The cult of the head start fails the learners it seeks to serve.”