How hard is too hard? Is there an optimal failure rate for learning? Robert Wilson, Amitai Shenhav, Mark Straccia, and Jonathan Cohen would say yes. In their 2018 study, The Eighty Five Percent Rule for Optimal Learning, the researchers set out to discover the “sweet spot” for difficulty in academia. They found that the spot where the most learning occurs –one that is not too hard so as to create frustration, but not so easy so as to not warrant doing– is a 15% failure rate. What does this mean for students? At its most simplistic level, it means that if you get 15% of the answers on an assessment wrong the test is at the optimal difficulty. 15% wrong? Wait that is only an 85% (or a B+), won’t that mess with my GPA (and perhaps my self-esteem)!?
While I don’t think we can go so far as to say that an 85% is the ideal grade, I do think that we can do more to design classes that both encourage and reward failure.