People forget at predictable rates regardless of other factors. For example, “People forget 40% of what they learned in 20 minutes and 77% of what they learned in six days.” “People forget 90% after one month.” “People forget 50-80% of what they’ve learned after one day and 97-98% after a month.”


There are many examples of claims that people forget X amount in Y time. These claims are all over the place, but each of them claims a universal truism without regard to the knowledge-level of the learner, the content of the learning concepts, the emotional salience of the knowledge or skill, the type of knowledge or skill, or the learning methods employed. These claims are often framed in terms of a forgetting curve. The most widespread claim are based on Hermann Ebbinghaus’s work from the 1800s.

Strength of Evidence Against

The strength of evidence against the claim of predictable forgetting rates is overwhelming and conclusive. Any perusal of the scientific research will find examples of forgetting curves that vary widely. Indeed, learning research that measures learners more than once is designed with the very premise that forgetting rates will vary; or why would the study be done in the first place? People certainly forget, but they forget at different rates depending on many factors.


Debunking Resources — Text-Based Web Pages


Debunking Resources — Videos

  • None that we know of…


Debunking Resources — Newspapers & Magazines

  • None that we know of…


Debunking Resources — Peer-Reviewed Scientific Articles as Examples

  • Corazzini, L. L., Thinus-Blanc, C., Nesa, M.-P., Geminiani, G. C., & Péruch, P. (2008). Differentiated forgetting rates of spatial knowledge in humans in the absence of repeated testing. Memory, 16(7), 678-688.
  • Wheeler, M. A., Ewers, M., & Buonanno, J. F. (2003). Different rates of forgetting following study versus test trials. Memory, 11(6), 571-580.


Debunking Resources — Research Reviews

  • None that we know of…