What we commonly know as memory (remembering something) is usually a general concept, because we usually talk about long-term memory .

But there are other types of memory, such as short-term memory and sensory memory , which participate in the formation of this more lasting memory.

One memory or many kinds of memory?

If we start to reflect on the capacities of human beings, it is very possible that we reach the conclusion that our species is characterized by having a good memory . Every day we learn and memorize things about the environment in which we live: who is the new president of a distant country, where we can find a national park whose photos have surprised us, what is the meaning of a word we did not know, etc.

Compared to ours, the memory of the other animals seems to be dwindling. In the end, they do not have a language from which to memorize complex concepts and which refer to elements that they have not seen directly. But… are you sure that’s all memory is?

After all, many migratory birds memorize the places they have to pass through to cover thousands of kilometers each year on their journey from North to South and vice versa. Similarly, salmon memorize the point in a river where they have to spawn and arrive there, after much effort and time spent at sea. Aren’t these examples proof that there are different types of memory?

Types of memory

The different memory types have their own particular way of working, but they all cooperate in the memorization process. Memory helps us adapt to our environment and marks us to define who we are; our identity. Without it we would be unable to learn, nor would we be able to make sense of our surroundings or ourselves.

But, what types of memory exist? what are the phases of memory? We will now answer these questions and explain how human memory works and how it allows us to remember events, data, experiences and emotions that we have lived in the past.

Early memory research

The first research on memory has its origin in the studies of Hermann Ebbinghaus , a German psychologist who at the end of the 19th century tried to decipher the fundamental laws of memory by studying nonsense syllables (BAT, SIT, HET).

Ebbinghaus’ theory of memory

One of his most outstanding achievements was the demonstration that higher mental functions could be studied in the laboratory in a scientific way. He also concluded that there was a “forgetting curve”, which shows the deterioration of memory over time from the moment of learning. Furthermore, formulated a theoretical model in which he defended that the memory mechanism requires repetition , so that the data we remember are associated with each other.

Bartlett takes the study of memory out of the laboratory

Ebbinghaus succeeded in having its approach used for many decades, which was called “the tradition of verbal learning”, but in 1932, Sir Frederick Bartlett began his studies on the functioning of memory in natural environments (Ebbinghaus conducted his studies on memory in the laboratory), giving rise to a new paradigm. Barlett, instead of using nonsense syllables, used stories, and introduced the theory of schemas to his research to explain their influence on memories .

Furthermore, he proposed that human beings remember by means of a general impression with some details , and that from such components they build a version considered to be close to the original; memory works with schemes, not with faithful replicas. Although it was criticized for its lack of methodological and statistical rigor, it stands out for its adherence to the constructivist theory of memory and for its contributions to the cultural formation of memory.

Miller and the current paradigm of how we store memories

Two decades later, in 1956, George Miller demonstrated that people can retain 5 to 7 elements at a time in short-term memory. These elements can be a single letter, a number, a word or an idea. Today, there is a consensus in cognitive psychology that a person interprets information based on prior knowledge, and thus builds his or her memories. It is therefore important to note that not all facts experienced are stored, as there is a selection of relevant facts , and what is not interesting is eliminated. Moreover, the facts experienced undergo a process of structuring and interpretation and, therefore, what is remembered is a perceived reality.

Experts in the study of memory agree that not only the cerebral cortex is involved in the memory process, but that other brain areas also participate in this process, for example the limbic system . It has also been shown that the left hemisphere processes verbal information, and the right hemisphere processes visual information. The ability to retain words is less than the ability to remember images.

Memory phases: coding, storage and retrieval

As demonstrated by Brenda Milner following her research with patients with memory disorders, memory is not located in one particular place in the brain, but rather consists of several systems that allow what are known as the three phases of memory : the coding , the storage and the retrieval .

  • The encoding is the process in which information is prepared for storage . In this first phase of memory, concentration, attention and motivation of the individual are very important.
  • The storage consists of retaining the data in the memory for later use .
  • The retrieval allows us to be able to find the information when we need it, i.e. to remember .

Classification and types of memory

There are different types of memory, and William James (1890) was a pioneer in formulating the distinction between them, as concluded that there was primary memory and secondary memory .

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Later, the so-called multistorage theory of Richard Atkinson and Richard Shiffrin appeared, which understands that information passes through different memory stores as it is processed. According to this theory, we have three different types of memory: sensory memory , short term memory (STM) and long term memory (LTM) . James’ primary and secondary memories would refer to the MCP and MLP respectively.

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Sensory memory

The sensory memory , which comes to us through the senses, is a very short memory (lasts between 200 and 300 milliseconds) and immediately disappears or is transmitted to short-term memory.

The mnestic information remains as long as necessary to be selectively addressed and identified for further processing. Thus, its usefulness has to do with the here and now, everything that happens in the present moment and to which one has to react in real time. The information can be visual (iconic), auditory (echoic), olfactory, etc.

Short term memory

When information in the sensory memory has been selected and attended to, it goes into short-term memory, also called operational or working memory . Its capacity is limited (7+-2 items), and it performs two functions. On the one hand, it keeps information in the mind when that information is not present. On the other hand, it can manipulate that information allowing it to intervene in other higher cognitive processes, and therefore, it is not a mere “memory drawer”.

Baddeley and Hitch, in 1974, instead of calling it “short term memory”, called it working memory because of its functional importance in cognitive processing, since it allows the fulfilment of cognitive tasks such as reasoning, understanding and problem solving. This concept abandons the idea that long-term memory depends on short-term memory, and this type of memory is fragmented into four sub-components

  • Phonological loop : is a specialized system that operates with verbal information, and allows to maintain the internal speech that is involved in short term memory.
  • Visuospatial agenda : operates in a similar way to the phonological loop, but its function is the active maintenance of information, but in this case with an image format, visuospatial. The visuospatial agenda would intervene, for example, or in the learning of an itinerary.
  • Episodic store : This system integrates information from a variety of sources, so that a multimodal (visual, spatial and verbal) and temporal representation of the current situation is created.
  • Executive system : Its function is to control and regulate the entire operating memory system.

Long-term memory

The long-term memory allows information to be stored permanently, and we can classify it into implicit and explicit memory.

Implicit memory

The implicit memory (also called procedural ) is stored unconsciously. It is involved in learning various skills and is activated automatically. Riding a bicycle or driving a car would not be possible without this type of memory.

Explicit memory

The explicit or declarative memory , is associated with consciousness or, at least, with conscious perception. It includes objective knowledge of people, places and things and what this means. Therefore, two types are distinguished: semantic and episodic memory.

  • Semantic memory : Refers to the mnestic information we have accumulated throughout our lives. It is the knowledge about the outside world (historical, geographical or scientific), the names of people and things, and their meaning, that we have learned throughout our lives. This kind of memory is necessary for the use of language. Knowing that Madrid is the capital of Spain is an example of this type of memory.
  • Episodic memory : It is the autobiographical memory that allows us to remember concrete facts or personal experiences, such as the first day of school, the birthday of one’s 18th birthday or the first day of university.

Un documental para entender mejor el funcionamiento de la memoria

Aquí te dejamos un capítulo del programa Redes en que varios psicólogos y neurocientíficos nos ilustran sobre la forma en que nuestro cerebro almacena y recupera los recuerdos.

Referencias bibliográficas:

Conrad C.D. (2010). Una revisión crítica de los efectos del estrés crónico en el aprendizaje espacial y la memoria. Progresos en Neuro-Psicofarmacología y Psiquiatría Biológica. 34 (5): 742 – 755.

Dudai Y. (2006). Reconstrucción: la ventaja de ser reorientado. Opinión actual en Neurobiología. 16 (2): 174 – 178.

Hacking, I. (1996). Ciencia de la memoria, política de la memoria. En P. Antze & M. Lambek (Eds.), Tense past: Ensayos culturales en el trauma y la memoria (pp. 67-87). Nueva York y Londres: Routledge.

Roediger, H.L., Dudai, Y. y Fitzpatrick S.M., eds. Ciencia de la Memoria: Conceptos. Nueva York: Oxford University Press, págs. 147 a 150.