Forgetting curve

The Ebbinghaus forgetting curve measures the decline of memory retention across time, showing how information is lost when there is no attempt to retain it. A related concept is the strength of memory that refers to the durability that memory traces in the brain. The stronger the memory, the longer period of time that a person is able to recall it. A typical graph of the forgetting curve purports to show that humans tend to halve their memory of newly learned knowledge in a matter of days or weeks unless they consciously review the learned material.

The forgetting curve supports one of the seven kinds of memory failure discussed in The Seven Sins of Memory: transience, which is the process of forgetting that occurs with the passage of time.

History

From 1880 to 1885, Hermann Ebbinghaus ran a limited, incomplete study on himself and published his hypothesis in 1885 as Über das Gedächtnis (later translated into English as Memory: A Contribution to Experimental Psychology). Ebbinghaus studied the memorisation of nonsense syllables, such as "WID" and "ZOF" (CVCs or Consonant–Vowel–Consonant) by repeatedly testing himself after various time periods and recording the results. He plotted these results on a graph creating what is now known as the "forgetting curve". Ebbinghaus investigated the rate of forgetting, but not the effect of spaced repetition on the increase in retrievability of memories.

Ebbinghaus's publication also included an equation to approximate his forgetting curve:

b

=

100

k

(

log

⁡

(

t

)

)

c

+

k

{\displaystyle b={\frac {100k}{(\log(t))^{c}+k}}}

Here,

b

{\displaystyle b}

represents 'Savings' expressed as a percentage, and

t

{\displaystyle t}

represents time in minutes, counting from one minute before end of learning.