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IN 1953 B.F. Skinner visited his daughter’s maths class. The Harvard psychologist found every pupil learning the same topic in the same way at the same speed. A few days later he built his first “teaching machine”, which let children tackle questions at their own pace. By the mid-1960s similar gizmos were being flogged by door-to-door salesmen. Within a few years, though, enthusiasm for them had fizzled out.
