There has been a long debate going on on the actual form of the Forgetting curve, but my question will be about its change when we review a previously memorised fact - Unfortunately, I couldn't seem to find too much information (or perhaps I used wrong terms) on this topic.

Maybe the most up-to-date and least divisive research paper on the topic of the actual form of the Forgetting curve would be Averell, L., & Heathcote, A. (2011). The form of the forgetting curve and the fate of memories. Journal of Mathematical Psychology, which I have seen referenced here multiple times. According to it the shape of the curve is best described as $$R(t) = a + (1-a)*b*(1+t)^{-β}$$ which would yield $1$ at $t=0$ if the encoding happened without a problem (which we assume did). My concrete question would be that how the three parameter change after repeated exposure to the fact (where we assume that at this specific $t_r$ the retention increases to $1$ again). I think it is fair to assume that it is going to be yet another curve describable with a Power function starting at $t_r$ which should have a higher asymptote as the original function.

A picture (although not scientific nor correct in terms of the actual form) illustrating my question has been already posted here at How are these review-forgetting curve calculated?, although for different purposes than mine.


1 Answer 1


Currently, I am working on various demonstration graphs of various spacing effect algorithms. From the research it seems like two of the parameters exist to constrain the outputted values...

The parameters a and b are also assumed bounded between zero and one, and hence R(t) is similarly bounded, which must necessarily be the case as R(t) is a probability. Enforcing this bound is important as otherwise data fits can be inflated (see Navarro, Pitt, & Myung, 2004, for further discussion).

I think Ebbinghaus' original function R(t) = e ^ -(t/s) (see this thread) can more easily explain things. t is time and s is the strength of the memory. After every review, s increases. If you plot this out, you see that if you increase s, the forgetting curve function flattens out.

  • 2
    $\begingroup$ Welcome to Psychology.SE. You suggested to "see Navarro, Pitt, & Myung, 2004, for further discussion" yet there is no reference information in order to find the article. $\endgroup$ Dec 16, 2018 at 15:14
  • $\begingroup$ @ChrisRogers I quoted a part from the paper that OP referenced. $\endgroup$ Dec 17, 2018 at 20:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.