# What is a forgetting curve?

We’ve all heard about “learning curve”, which basically means the rate at which a person is gaining experience or new skills. But do you know what a “forgetting curve” is?

##### A great pioneer

The origins of learning curve dates back to 1885, when the German psychologist Hermann Ebbinghaus published limited, experimental studies on himself in his work “Über das Gedächtnis”. Ebbinghaus assumed that the process of committing something to memory involved the formation of new associations and that these associations would be strengthened through repetition.

##### Original study

To observe this process, Ebbinghaus devised a set of items to be committed to memory that would have no previous associations, the so-called “nonsense syllables”. These consist of a sequence of consonant, vowel, and consonant (CVC) that does not spell anything in one’s language . In English, CAJ would be an example. Ebbinghaus constructed lists of around 20 of these items and then proceeded to memorize these lists systematically. He would read the first item, say it to himself, then go on to the next item, repeat it to himself, and so on, spending the same amount of time on each item. One complete run through the list constituted a single repetition.

##### Learning curve

After some series of repetitions, Ebbinghaus would attempt to recall the items on the list. It turned out that his ability to recall the items improved as the number of repetitions went up, rapidly at first and then more slowly, until finally the list was mastered. This was the world’s first learning curve.

##### Forgetting curve

On the other hand, Ebbinghaus noted that the level of retention with time had the following shape:

##### For math lovers: the formula

Ebbinghaus came up with the following formula that describes the exponential nature of forgetting:

where R is memory retention, S is the relative strength of memory, and t is the time.

##### Forgetting speed

To test retention, Ebbinghaus practiced a list until he was able to repeat the items correctly twice in a row. He then waited varying lengths of time before testing himself again. Forgetting turned out to occur most rapidly soon after the end of practice, but the rate of forgetting slowed as time went on and fewer items could be recalled. On this graph, you can see that the forgetting speed after the 4th repetition (blue curve) is much slower than the initial forgetting speed (red curve).

##### Employee training

Today, more than 130 years after Ebbinghaus’ publication, the training actions of companies for their employees still have very little medium and long-term impact on employee’s skills. “Training” is often either a regulatory requirement or a way to offer employees a benefit other than salary increase or promotion.
For companies who genuinely want to train employees, it’s time to rethink the way we train and how to make an impact on the company’s performance. In average with an usual training session, whether online or offline, team members forget 80% of what they learnt after 2 months. This can be interpreted by saying that roughly 80% of the training investment is lost.

##### Creating experts

People who are considered as experts are those who most “learnt while doing” because they have repeated an action plenty of times, as part of their daily job. A repetition-based training is most relevant for:

• avoiding black-swan events: high-impact, low-probability events such as accident prevention, regulatory and legal risks
• employee onboarding: to reach quickly a high-level of knowledge and maintain it, as the quantity of information to assimilate may be impressive sometimes: this allows to remember processes even before having to use them in practice.
• sales and support teams: to have a better knowledge or product, services and issue that are not seen on a daily or weekly basis.
• cross-functional training, to strategically empower employee to be the company leaders of tomorrow by offering them a training beyond their area of expertise