Also, I had not got all of the psychological bugs out of the idea. In successive runs through the machine, students did indeed learn very rapidly, and so far everything looked encouraging. But then, and also in more recent experimentation, when I checked on that learning by repeating some of the material verbatim but in a little different context a week later, very little appeared left. If the test was rephrased and in a different context, almost nothing seemed retained.
— 📖 Teaching Machines — The History of Personalized Learning, quoting, idk, Skinner?