To optimize the learning of a physical or cognitive skill, one must structure practice in a way that maintains a failure rate of approximately 15% (the 85% success rule), as this level of difficulty best stimulates cerebral plasticity.

noli's read

This recommendation is based on a mathematical modeling study conducted by Wilson et al. (2019) and published in Nature Communications. By analyzing machine learning algorithms and data from animal research, the researchers established that a 15% error rate represents the perfect mathematical equilibrium to maximize the speed of task assimilation. This concept resonates with classic theories in educational psychology (the zone of proximal development), which value moderate difficulty to maintain engagement. However, the strict application of this specific percentage during physical training or complex human learning has not been the subject of randomized controlled trials (RCT). In practice, this figure serves as an inspiring analogy rather than an absolute clinical target, as field research remains primarily observational. Exposing oneself to moderate difficulty is therefore scientifically validated for progress, even if it is difficult to precisely measure one's error rate in real time.

the sources

1. 1NIH Office of Dietary Supplements 2026
2. 2Manson JE et al. 2019
3. 3Bhatt DL et al. 2019
4. 4Khan SU, Lone AN, Khan MS, et al. 2021
5. 5Liao Y, Xie B, Zhang H, et al. 2019
6. 6hubermanprotocols.com (fan reference guide)