For a sound, image or thought to return to mind when it is no longer present, it has to be represented in the mind without the original stimulus being present. Therefore your mind literally recreates the memory based on your storage of it. The three main memory storage systems are sensory, verbal and motor (physical actions).
- Sensory representations store information in a sensory bank, such as the sound of an ocean wave, or the image of a dog on a leash.
- People rely on visual representations to be able to recall how to walk to the train station for example.
- Visual representations are like pictures that can be mentally examined or manipulated.
- Although many representations are stored in sensory modes, much of the time people think using verbal representations – information stored in words.
- Try to imagine something in your mind without thinking it out with words, hard right? It’s almost impossible to think with sounds and images alone, as the mind works hard to make sense of your memories by describing them with words.
THE ANATOMY OF MEMORY
In 1890 William James proposed a distinction between two kinds of memory, which he called primary and secondary memory. Primary memory is immediate memory for information momentarily held in consciousness, such as a telephone number. Secondary memory is the vast store of information that is unconscious except when called back into primary memory. This system for describing memory was called the standard model of memory and it looks a little something like this: Don’t mind the crude drawing. Basically the process for memory is as follows:
- Stimulus enters the sensory registers.
- Some information enters short term memory and is then passed on for storage in long term memory.
- Information can be lost from any of the sensory stores, usually if it is not important or if a traumatic event has interfered with memory consolidation/retrieval.
- Short term memory can be rehearsed to keep it in there longer and to help consolidate the information for long term memory storage – for example, if you’re told a phone number and you haven’t got a pen, repeating it in your head will keep it in your short term memory until you can write it down, after a bit of rehearsal it might end up in long term memory and you will be able to recall it easily.
- Consolidated information in long term memory storage can be retrieved and brought back to short term memory with the help of retrieval cues – images, words, sounds, smells or actions that trigger past memories.
Sensory Registers – Sensory registers hold information about a perceived stimulus for a fraction of a second after the stimulus disappears, allowing a mental representation of it to remain in memory briefly for further processing. It contains two storage spaces, they are:
- Iconic Storage – briefly holds visual information – people retain a mental image of what they have seen shortly after it disappears from their vision.
- Echoic Storage – briefly holds auditory information – this is how you are able to hum the melody of a song you just listened to for example.
Short Term Memory – Short term memory (STM), is a memory store that holds a small amount of information in consciousness – such as a phone number – for 20 to 30 seconds, until the person makes a deliberate effort to maintain it longer by repeating it over and over. Limited Capacity – Short term memory has a limited capacity, that is it can’t hold too much information at a time. To assess the capacity of STM, psychologists assess participants digit span, that is the number of numbers a person can hold in their mind at once. It has been established that the average person can hold 7 pieces of information in their short term memory at a time, with a normal range of 5 to 9 items. The easy to remember formula for this is 7+/- 2 (7 plus or minus 2). You might be thinking to yourself, wait a minute… my mobile number is about 10 digits long, how can I possibly keep that many digits in my short term memory? We do this by utilising a little tool called chunking. Basically, we can hold 5-9 pieces of information in our short term memory at a time, but this also includes chunks of information. So in the case of a mobile number of 10 digits such as: 0428790526, we instead remember it like this 0428 790 526, this chunks the ten digits into three easy to remember chunks of information, allowing us to hold more in our short term memory. Rehearsal – People can control the information stored in short term memory. If I tell you my phone number and ask you to remember it and then I start counting backwards from 100, I can potentially mess with your short term memory; placing different numbers in your head space. Assuming I tell you my phone number, and decide not to mess with your head, you can repeat the number over and over again until you find a piece of paper and a pen to write it down. This kind of repetition to maintain information in your STM is called maintenance rehearsal. Rehearsal is also important if you want to commit the information to long term memory, for example if you have ever needed to memorise lines from a play, you would know that simply repeating the lines over and over won’t help commit the memory. You have to say them out loud, in character and reflect on the meaning of each word and the emotions implied. This is a much more elaborate method of rehearsing rather than just repeating the information in your hand, and so it is fittingly called elaborative rehearsal. Rehearsing information this way is much more likely to be committed to long term memory, another example of elaborative rehearsal ; teachers use this method frequently to remember their student’s names: “Dan the Man”, “Red Fred” etc. Long Term Memory – While most information drops out of memory after it is no longer of use, more important information gets stashed away in long term memory (LTM), where representations of facts, images, thoughts, feelings, skills and experiences may reside for as long as a lifetime. According to the standard model, the longer information remains in STM, the more likely it is to make a permanent impression in LTM. Recovering information from LTM, known as retrieval, involves bringing it back to STM.
- Why does psychology distinguish between long term and short term memory? Simply because STM is brief, limited in capacity and quickly accessed. While LTM is enduring, virtually limitless, but more difficult to access.
- Another reason emerged as psychologists tested memory using free-recall tasks. In free-recall tasks, the experimenter presents participants with a list of words, one at a time, and then asks them to recall as many as possible. When the delay between presentation of the list and recall is short, participants demonstrate a phenomenon known as the serial position effect: a tendency to remember information towards the beginning and end of a list rather than in the middle.
The reason we have this process for interpreting and storing memory is that in any given second we are exposed to countless sounds, images, smells, sensations all in one instant. If we were to take in every scrap of sensory information that surrounded us, our brain would probably shut down due to sensory overload. This is why we only acknowledge a small fraction of sensory information which stores in the sensory registers, while the important information in that cluster goes into short term memory for immediate attention, and very important information gets filed away in long term storage. To illustrate the process of memory imagine a scenario where you and a friend are at a park on a windy day. The sound of the wind is intense, the birds are chirping, you can hear people talking the the background, cars driving on the street nearby, dogs barking and so on. You can also see all of these things, and can even see things in the distance that you cannot hear. On top of this you can smell the air, the cigarette smoke of a nearby smoker, the food in your friend’s hand etc. Our mind is incapable of processing all of this information at one time, which is why only immediately important sensory information is processed, while the words your friend speaks to you are immediately transported to short term memory, so you can dwell on what they have said before responding.
As the conversation flows and you become more involved in it you might find yourself blocking out other sensory information, and might forget that there are dogs catching frisbees nearby for example. Also, as the conversation grows and changes, you will find that your short term memory is no longer processing what you two were talking about 10 minutes ago for example, and is no busy concentrating on what you are currently talking about. This is because information leaves short term memory when it is no longer of use to the current situation. If your friend were to tell you something extremely important, then you might transfer that information into long term memory storage, so that you can never forget it.