I didn’t look closely yet, but people here might be interested in this.
Despite a long history of research, it is unclear why particular difficulty levels might be best for learning.
However, scientists from the University of Arizona say they have now found the “Goldilocks zone” – with their data suggesting people who fail 15 per cent of the time learn the fastest.
Researchers created machine-learning experiments in which they taught computers simple tasks like categorising patterns or arranging numbers. The computers learnt fastest when they got 85 per cent of answers correct, according to the paper published in Nature Communications .