How is the human memory tested

Milestones in memory research

Hermann Ebbinghaus: his own guinea pig

The Berlin psychologist Hermann Ebbinghaus came up with the revolutionary idea around 1885 of experimentally researching memory. He was the test director and test person in one person: Ebbinghaus experimented with a wealth of meaningless syllables such as "WUX", "CAZ" and "BIJ". He meticulously noted how many of them he kept. He took into account the number of repetitions as well as the influence of time.

It turned out that after a one-time study, Ebbinghaus could never reproduce more than seven syllables. And he forgot these seconds later: Ebbinghaus had tested his short-term memory for the first time.

Shereshevskii: reporter with perfect memory

In the 1920s, the Russian neuropsychologist Alexander Luria investigated an amazing memory: the newspaper reporter Shereshevskii was able to memorize long lists of words, numbers and meaningless syllables in a very short time. He later reproduced it without any errors.

Once he was presented with a mathematical formula with 30 elements. He was able to repeat it immediately - even after 15 years. Shereshevskii achieved this thanks to an intense visual imagination that scientists refer to as "synesthesia".

Because the words evoked visual impressions in him. Usually, like the ancient mnemonics, he mentally placed each image on a familiar street. If he wanted to remember, he mentally ran down the street again and collected the pictures.

The researchers were particularly interested in the fact that his excellent memory also gave Shereshevskii many disadvantages: for example, he could not concentrate well on the meaning of what was being said - his pictures prevented him from doing so.

He also had difficulty understanding metaphors or poetry. In general, Shereshevskii, crammed with details, found it difficult to abstract and discover similarities between events.

H.M .: a sad case brings new insights

In 1953, American doctors removed the suspected disease triggers in the brain of the epileptic H.M. Although the procedure relieved the seizures, H.M. suffered a devastating memory loss. Since then, he has not been able to remember anything new for more than a few minutes. When his doctor entered the room, he always greeted her as if he were seeing her for the first time.

However, H.M.'s memory was still intact up to the moment of the operation. The scientists derived important insights into the functioning of memory from his case: The parts of the brain removed by H.M. are not required for short-term memories. But neither are they the final storage locations for the long-term content of previously acquired knowledge.

Thanks to similar observations in patients with brain injuries, a map of the brain regions and their functions has emerged over the years.