Long-term Memory

Long-term Memory is the one that makes it possible for you to recall a face, a place or your own pet, when you see them. The information stored in here, remains for a life-time and its storage capacity is endless.

 

Working with Long-term Memory

Long-term memory is the most complex of all memory types. There are different forms of working with it, for it and within it.

Repetition, for example, is a way of getting Long-term memory and short-term memory to interact with each other. It will allow the information’s transference from Short-term to Long-term, at the same time that it also helps the Long-term storage information to be able to also have a place and remain in the Short-term where it’s easily accessed.

Another way of working with it is through coding, which basically equates to giving some meaning to the pieces of information in order to make them easier to remember. This will help the recuperation process which is, according to some authors, the component which is truly responsible for our inability to recall certain memories.

Different Memories in one Memory?

But, speaking about Long-term Memory isn’t that simple, and different authors have presented different theories. Long-term Memory allows us to be who we are, it’s a permanent storage of knowledge and information, and it will have a great impact in the way we perceive the world around us.

There are many theories around Long-term Memory, but the one which seems to be the most widely accepted is the one that divided Long-term Memory into two separated sections: declarative memory and procedural memory.

 

Declarative Memory

Declarative memory refers to facts and situations that can be recalled, as in, we can say what happened or took place, how something looks or feels like… It’s something conscious and that gives us the possibility of expressing it. This can, by itself, be divided into episodic memory and semantic memory.

Episodic memory refers to particular events and specific episodes we lived and we’re now able to remember with surprising detail. It’s linked to an event or specific occasion.

Semantic memory is more about knowledge and the significance that we attributed to something. Here, the knowledge is stored under a form of words and symbols, and it contains general knowledge about the world, about facts and not particular events.

Procedural Memory

Also known as implicit memory, procedural memory doesn’t really imply an active and conscious effort from us. It’s related to motor or cognitive skills that are automatically brought up in order to do or achieve something, like playing a guitar or driving a car.

It also reflects, for example, grammar acquisition. You can speak correctly without being able to explain why it is indeed correct. The classical conditioning is associated to procedural memory too, since you can’t, for example, consciously explain why you fear elevators.

This kind of memory can be affected by abnormally high levels of stress. In these occasions we seem to forget, temporarily, how to do something that we’re usually able to do very easily.

 

So, if it lasts a life-time, why can’t you remember everything?

As you may be thinking right now, you can’t remember everything you want to, at least, not exactly as it happened. There are some gaps here or there. Well, that’s totally normal.

There are many diseases that can affect long-term memory, such as Alzheimer’s, Dementia, Schizophrenia or Parkinson’s, but even a perfectly normal and healthy adult can’t recall anything he or she wanted. For example, it’s quite normal for an adult to remember with more intensity and details, events that occurred during adolescence that those during his middle-age. Maybe because, teenagers live everything with amplified intensity and when you are older you give less and less importance to some situations and they kind of fade away in your memory.

 

Flashbulb Memory Theory

Brown and Kulik (1977) developed some investigation in this area, regarding episodic memory, where they tried to prove that emotions could indeed affect our memory.

They centered their investigation in specific historical events and asked people how they remembered it (the most famous experiment being how they remembered the news about John Kennedy’s death). These memories were too vivid and had many details, but they weren’t accurate…

The fact is, that a vivid and detailed memory doesn’t mean a correct description of the event, because memories (specially the older ones) are thought of, repeated and elaborated by our mind, especially if they had a great emotional impact. Our brain will mix what really happened with what we think happened and what we think should had happened.

So, most of the time, these memories are very far-off from the reality of the described event. They are like flashes of a camera that pops up in our mind and we interpret them accordingly with the importance and distinctiveness of the event, its consequences, how surprised we were and the proximity and personal involvement with the event.

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Short-term Memory

Short-term memory refers to memories which remain for around 20-30 seconds. It’s a very short time-frame and there’s limits to the amount of them as well. Some experiments performed by Petersen and Petersen (1959) suggest that the maximum capacity of Short-term memory is around 7(+/- 2) chunks of information (also called The Seven Plus or Minus Two Theory).

However, this is something really difficult to measure, due to the significance that an information may or may not have for a person. For example, four random numbers can be four pieces of information, but they could also be a date which might mean something for a specific person, so it will become just one piece of information for such an individual, and so, theoretically, that person would be able to remember more pieces of information that another one, for whom the numbers didn’t get memorized as a date, since it didn’t mean anything to them.

 

Chunking

Based on this information, scientists determined chunking as a method to improve our Short-term Memory capacity. Giving some meaning to the information, as well as a favorable context of learning, a subject would be able to retain a somewhat larger amount of information.

In the same way, giving some tips to the subject, would improve his or her ability to recall the information.

 

Serial Position Effect

There are a lot of circumstances that can affect our Short-term memory capacity and the serial position is definitely one of them.

Some experiments revealed that when some words are presented in a row, or sequence, the subject tends to remember more efficiently the first ones (primacy effect) and last ones (recency effect), while the ones in the middle of the series are frequently forgotten.

This can have some practical implications, as, for example, it could be the explanation for the fact that the first impressions you have, regarding other people, can have such a great impact on your perception of them.

Sensory Memory

Sensory memory refers to the memories which are brought on and retained by the senses. This kind of memory is extremely short-term and, since it’s gathered by our senses, you have different types of sensory memories, such as olfactory, tactile, visual, etc.

Many experiences were held in which the goal was to demonstrate how this specific kind of memory actually works, but the most studied and researched types were, without a doubt, the iconic memory and the echoic memory.

One of the most famous experiments was performed by George Sperling in the 1960’s and it was a study on the field of iconic memory. The experiment consisted of presenting a group of letters (with no particular meaning) to the subjects for a short period of time (less than a second) and then asking the subjects to state back the letters they remember. The results were similar every time the experiment was conducted: the subjects can remember about 3 or 4 of them.

There were many variations made to this experiment. Sperling himself tried to add some sound to each row of letters, others tried to manipulate the number of stimuli or asked the subjects to recall one specific part of the stimuli, pointing out its position. The more senses the stimuli affected, the easier is became for the subject to remember it. However, in all experiments, one very important conclusion was made: this type of memory has a really short lifespan, or timeframe.

Still in the 60’s, experiments based on echoic memory were conducted as well. They consisted in telling a test subject a list of numbers and he or she should recall them immediately after they were recited to him. The word immediately is quite important here, because some variations were tried as well, and if the subject waited a couple seconds more, the memory of the numbers would fade, because that’s how long the sensory memory lasts: about 1 or 2 seconds.

Sensory memory is often confused with short-term memory, but in reality, they’re quite different, not only because sensory memory lasts for such little time, while short-term memory lasts for approximately 20 to 30 seconds, but also because sensory memory cannot be controlled by the conscious mind. The brain processes the information and stores it automatically and Sensory Memory cannot be prolonged or made to live on for longer, as Short-term or Long-term memory.

Memory, a field of study

Memory can be defined as our ability to retain information and remember it when we later need it. This is one of the most studied fields in Cognitive Psychology and it has been approached in many different ways throughout the years.

There was a time where the memory capacity comprised the majority of the exercises in intelligence tests. Today, we know that it’s not accurate to directly relate memory with intelligence, but it is a fact that our memory is important to almost everything.

Therefore, many scientists tried to study and test the human memory. The initial tests were made with a list of words that the individual should try to memorize. It was just a list with unrelated words and soon enough, they understood that it had no scientific validity.

But the studies evolved and the theme was approached in many different ways, from different points of view. There were those who tried to determine the structure of our memory, as in, how it was organized, others, the process, the way it works and how the information is retained in our memory, the way it’s coded and how we recover it, and there were even the ones who focused on the oblivion and how information disappeared from our memory.

Atkinson–Shiffrin memory model

After William James had defined that there are two different systems of memory (Primary Memory, which is what is conscious in every moment, equivalent to what we call today Short-term Memory and Secondary Memory, which would be equivalent to what we call Long-term Memory, with James defining it as what is permanently in our mind) Atkinson and Shiffrin developed, in 1968, a model of how memory would work.

This model talked about different storages of information, each one with its own characteristics.

The first storage, called Sensory Memory, is the one that receives the sensory input from the environment. It has a very short focus time (1 sec) but it can receive unlimited information.

When something gets your attention, you stay focused on it and this information will pass through to the second storage: Short-term Memory. Here, the information stays for a longer time period, but not by much. Actually, scientists talk about some 20 to 30 seconds of permanency in this storage. The Short-term memory has an even more interesting characteristic: it cannot store too much information (nearly 7 pieces of information at a time).

Then, the repetition of information, its meaning and context will allow some of it to pass through to the third storage: Long-term memory. With unlimited space, the long-term memory will retain the information, supposedly for the rest of your life… So, why can’t you remember it whenever you need it? Well, according to Atkinson and Shiffrin the inability to recover the information doesn’t mean that it isn’t there…

I will talk about each one of these storages with more details soon and presenting you some studies about them in the following posts.