When talking about memory, you probably think about remembering that unforgettable moment in life. Maybe you think about that happy childhood memory, or that person you used to know that was important to you. But memory is so much more than that. Reading, walking, recognizing the smell of your favorite dish, it is all made possible because of the memory. But is actually meant with the human memory? How does it work? And why do we forget? In this article, we’ll explain you everything you need to know about the human memory.
Our memory is our ability to encode, store and recall information from our brain.
But what does this actually mean? We will go through this process step by step:
All the information that our brain receives through our senses, will first be transformed into a form that the memory will be able to store. This event begins with perception through the senses. The way the information will be encoded depends on what kind of information it is and through what senses your brain received it. In addition, what will be encoded to be stored within the memory can be affected by mood. For example, a stressful situation can cause your brain to prevent you from storing memories at all.
After all the received information is encoded, the brain is able to retain this information within the memory. But, there actually isn’t a specific place within the human brain where all the memories are stored. The different types of memories are stored across different interconnected regions of the brain.
This stage refers to re-accessing the information that is stored within the memory. For example, when you think of a happy childhood memory you are retrieving information that was stored within your memory years ago. Although this might seem like a single memory for you, recalling a smell, sight, sound or feeling are all separate memories stored in different regions of the brain. When thinking of a certain memory, you access different parts of your brain and connect those pieces of information.
Recalling the memories and experiences that are stored within our brain has the purpose of affecting future actions. If the already occurred actions wouldn’t be stored and couldn’t be recalled, it would not only be impossible to remember that happy childhood memory, but it would also be impossible to learn. For example, language skills, relationships or personal identity wouldn’t be able to develop.
Like already mentioned, the human memory doesn’t exist out of a single type of memory. It exists out of different memory systems. When we store a memory, we are receiving, encoding and storing information. How this information will be stored and for how long depends on what kind of information it is. Depending on the information, a different memory type will store the information.
There are three memory types, which have their own way of operating but they still cooperate in the process of memorization. These types can be seen as the three steps that are necessary for creating a long-term memory. The three types of memory are the long-term memory, the short-term memory and the episodic memory.
The sensory memory is considered the first stage of memory. The sensory memory involves registering huge amounts of information about the environment, for a very short time. It allows you to retain the information you receive through your senses after the original stimuli has ended. The process of receiving information through your senses is also called sensation.
It acts as a buffer for the stimuli received by hearing, seeing, feeling, smelling and tasting, which will be retained accurately but only for a couple of seconds. Whilst the senses are responsible for receiving all these stimuli, the stimuli are processed by your perception within your brain. The process of the senses receiving all these stimuli that occurs before perceptions can be created is called the sensation process.
The sensory memory can be divided in the following 5 sensory memory systems:
Haptic memory (touch)
The haptic memory recalls information that was originally collected by the sense of touch. When thinking of raindrops on your face, you might recall how this feels. This is made possible by the memory saving these types of information via the haptic memory.
Echoic memory (hearing)
The echoic memory, also known as auditory memory, is the sensory memory that stores sound. You can probably recall your favourite song as if it is playing right now, this is a memory that’s been stored after being collected by the echoic memory.
Iconic memory (sight)
The iconic memory is the sensory memory that stores visual information after receiving this information through your sight. While looking at your screen and reading this text, your iconic memory stores information for a couple of seconds. If you close your eyes, you can probably recall what you are seeing right now.
Olfactory memory (smell)
The olfactory memory refers to the recollection of odours. When thinking of your favourite dish or flower, you might even remember the smell of it. This memory has been stored within your memory through the olfactory memory.
Gustatory memory (taste)
The gustatory memory is the sensory memory that is responsible for recalling taste. While eating or drinking, a lot of information is stored within the memory through our gustatory memory. You can probably remember the taste of your favourite dish, because the gustatory memory helped to store this information within your memory.
Your short-term memory is responsible for holding a small amount of information for a short period of time. This information is processed through the sensory memory in your short-term memory. The short-term memory holds this small amount of information in an active, quickly accessible state. The memories stored within the short-term memory will last for about 10 to 15 seconds.
Say you're remembering a phone number while you are dial the number before you call it. You read a couple of digits, try to remember them and enter the digits. At this moment you remember the digits and probably recalling the digits within your head, while you’ll forget them in the long term. In this situation, you are using your short-term memory.
The working memory
The working memory is a memory system that is responsible for storing and managing information that is required together with other cognitive skills to perform cognitive tasks, such as learning and reasoning. The working memory focusses on memory-in-action, it has the ability to remember and use relevant information while in the middle of an activity.
The difference between your short term and working memory
The short-term memory and working memory sound quite similar to each other, both memory systems hold information for just a couple of seconds. Yet, the two memory systems are distinct. While the short-term memory only retains information, the working memory both retains and retrieves information. The working memory is used when performing a task where you have to remember and do something at the same time. Such as responding to something that has been said in a currently active conversation.
The long-term memory is the memory system that stores information for a longer period of time. This duration can vary from a few minutes to an entire lifetime. Information reaches the long-term memory by registering information through the sensory memory to the short-term memory, to be eventually stored within the long-term memory. But not all information will be stored within your long-term memory. Through the process of rehearsal, short-term memories might become a long-term memory. This means that if you rehears information long enough, you eventually will store it within your long-term memory. How long this will take depends on what you are trying to learn and the importance of it, it’s easier for you to remember the birthday of someone important to you than the colour of the hair of someone you walked past yesterday.
The long-term memory exists out of the following 2 memory systems:
Like previously mentioned, the three stages that are involved in remembering information are encoding, storage and retrieval. But how do we relate this to the sensory memory, the short-term memory and the long-term memory? We’ll go through the process of how a memory is stored from the sensory input to the long-term memory.
A memory starts with information that is detected by the senses. After the information is being detected by hearing, seeing, smelling, feeling or tasting, it enters the sensory memory. This information will be stored for about half a second, before it’s forgotten. If the detected information is considered relevant enough to be registered, it will enter the short-term memory. Otherwise, it’ll be forgotten.
In order for the sensory memory to be retained for a longer period, it has to convert from the sensory memory to the short-term memory. Just like your sensory memory, your short-term memory only stores information temporarily. If not processed to the long-term memory, the information within the short-term memory will be forgotten after about 20 to 45 seconds. Unlike the sensory memory that stores the complete perception perceived by your senses, the short-term memory only stores your interpretation of the information.
The capacity of the short-term memory is very limited, most people are able to store between five and nine subjects. If these subjects won’t be processed into your long-term memory, your brain will usually forget them within a minute.
Although the memories in your short-term memory will be forgotten after about 20 to 45 seconds, rehearsal of the information converts them into the long-term memory. The information will be encoded by making judgements, assessments about meaning, by relevance and the significance of that information. If the encoding of information won’t happen, the information won’t be stored within the long-term memory.
The information that is stored within the long-term memory, can be retrieved for up to any duration. Different to the short-term memory, the long-term memory has an unlimited capacity. Yet, not all information received through your senses will reach the long-term memory if it isn't important enough, it might not even reach the short-term memory. Even if the information would reach the long-term memory, the information that is stored can be forgotten through interference or retrieval failure.
The stages of the memory process are visualized in the image below.
Despite our long-term memory having an unlimited capacity, it occurs that you can fail to recall information. So, forgetting isn’t usually about actually losing or erasing this information from your long term memory. There are four major reasons why we forget, these are:
One of the factors that play a huge role in forgetting is time. When time passes, memories that have not been accessed could fade away. A memory can be stored and retrieved when you are learning something new or when you are connecting new information with existing memories that are already stored within your brain. If this information will not be retrieved and rehearsed over time, these memory traces will start to fade away. This is also called the decay theory. This can be seen as a moment that was important to you a long time ago. At first, you remember everything about that moment, but after not thinking about it for years the details of that moment starts to fade away.
Memories can also be forgotten because of interference. Some memories you have stored within your brain can interfere with other memories. This can occur when information is very similar to the other information within your memory. This is also called the interference theory. Maybe you have a memory of one of your holidays, which can be in fact a memory of another holiday. You can mix up the memory of these two similar situations, causing your brain to forget the original one.
It can occur that losing a memory isn’t caused by forgetting. Sometimes losing a memory happens because it never actually made it into the long-term memory at all. This is a result of the encoding that often fails, preventing information to convert from the short- to the long-term memory. Like when you are learning from a book and you thought you knew everything that was needed for a test, but suddenly the memory is gone. Failing to store a memory can have lots of causes, such as a stressful situation, learning from a book until your memory is overloaded with new information or a lack of focus while you weren’t aware of it.
Besides forgetting a memory as a result of the normal forgetting processes of the memory, there are many reasons that can cause memory loss. How these causes might affect the brain or if they even affect the memory at all differs per person and situation. A couple of examples of causes of memory loss are:
Because your brain adapts to different stimuli it gets (also known as neuro plasticity), it’s possible to improve your memory. You can do this by challenging your brain to force your memory to get to work. Besides challenging your brain, there is a lot you can adjust in your lifestyle to improve your memory. You can improve your memory by:
Now you know that your memory isn’t just “your memory”, but actually the combination of your sensory, short-term and long-term memory. With them combined, your memory is able to process what your senses gather, define conclusions and store important information!