Stages of Memory Encoding Storage and Retrieval
Saul McLeod published 2013
“Memory is the process of maintaining information over time.” (Matlin, 2005)
“Memory is the means by which we draw on our past experiences in order to use this information in the present’ (Sternberg, 1999).
Memory is the term given to the structures and processes involved in the storage and subsequent retrieval of information.
Memory is essential to all our lives. Without a memory of the past, we cannot operate in the present or think about the future. We would not be able to remember what we did yesterday, what we have done today or what we plan to do tomorrow. Without memory, we could not learn anything.
Memory is involved in processing vast amounts of information. This information takes many different forms, e.g. images, sounds or meaning.
For psychologists the term memory covers three important aspects of information processing:
1. Memory Encoding
When information comes into our memory system (from sensory input), it needs to be changed into a form that the system can cope with, so that it can be stored. Think of this as similar to changing your money into a different currency when you travel from one country to another. For example, a word which is seen (in a book) may be stored if it is changed (encoded) into a sound or a meaning (i.e. semantic processing).
There are three main ways in which information can be encoded (changed):
1. Visual (picture)
2. Acoustic (sound)
3. Semantic (meaning)
For example, how do you remember a telephone number you have looked up in the phone book? If you can see it then you are using visual coding, but if you are repeating it to yourself you are using acoustic coding (by sound).
Evidence suggests that this is the principle coding system in short-term memory (STM) is acoustic coding. When a person is presented with a list of numbers and letters, they will try to hold them in STM by rehearsing them (verbally). Rehearsal is a verbal process regardless of whether the list of items is presented acoustically (someone reads them out), or visually (on a sheet of paper).
The principle encoding system in long-term memory (LTM) appears to be semantic coding (by meaning). However, information in LTM can also be coded both visually and acoustically.
2. Memory Storage
This concerns the nature of memory stores, i.e., where the information is stored, how long the memory lasts for (duration), how much can be stored at any time (capacity) and what kind of information is held. The way we store information affects the way we retrieve it. There has been a significant amount of research regarding the differences between Short Term Memory (STM ) and Long Term Memory (LTM).
Most adults can store between 5 and 9 items in their short-term memory. Miller (1956) put this idea forward and he called it the magic number 7. He though that short-term memory capacity was 7 (plus or minus 2) items because it only had a certain number of “slots” in which items could be stored.
However, Miller didn’t specify the amount of information that can be held in each slot. Indeed, if we can “chunk” information together we can store a lot more information in our short-term memory. In contrast, the capacity of LTM is thought to be unlimited.
Information can only be stored for a brief duration in STM (0-30 seconds), but LTM can last a lifetime.
3. Memory Retrieval
This refers to getting information out storage. If we can’t remember something, it may be because we are unable to retrieve it. When we are asked to retrieve something from memory, the differences between STM and LTM become very clear.
STM is stored and retrieved sequentially. For example, if a group of participants are given a list of words to remember, and then asked to recall the fourth word on the list, participants go through the list in the order they heard it in order to retrieve the information.
LTM is stored and retrieved by association. This is why you can remember what you went upstairs for if you go back to the room where you first thought about it.
Organizing information can help aid retrieval. You can organize information in sequences (such as alphabetically, by size or by time). Imagine a patient being discharged from hospital whose treatment involved taking various pills at various times, changing their dressing and doing exercises. If the doctor gives these instructions in the order which they must be carried out throughout the day (i.e., in the sequence of time), this will help the patient remember them.
Criticisms of Memory Experiments
A large part of the research on memory is based on experiments conducted in laboratories. Those who take part in the experiments - the participants - are asked to perform tasks such as recalling lists of words and numbers. Both the setting - the laboratory - and the tasks are a long way from everyday life. In many cases, the setting is artificial and the tasks fairly meaningless. Does this matter?
Psychologists use the term ecological validity to refer to the extent to which the findings of research studies can be generalized to other settings. An experiment has high ecological validity if its findings can be generalized, that is applied or extended, to settings outside the laboratory.
It is often assumed that if an experiment is realistic or true-to-life, then there is a greater likelihood that its findings can be generalized. If it is not realistic (if the laboratory setting and the tasks are artificial) then there is less likelihood that the findings can be generalized. In this case, the experiment will have low ecological validity.
Many experiments designed to investigate memory have been criticized for having low ecological validity. First, the laboratory is an artificial situation. People are removed from their normal social settings and asked to take part in a psychological experiment. They are directed by an 'experimenter' and may be placed in the company of complete strangers. For many people, this is a brand new experience, far removed from their everyday lives. Will this setting affect their actions, will they behave normally?
Often, the tasks participants are asked to perform can appear artificial and meaningless. Few, if any, people would attempt to memorize and recall a list of unconnected words in their daily lives. And it is not clear how tasks such as this relate to the use of memory in everyday life. The artificiality of many experiments has led some researchers to question whether their findings can be generalized to real life. As a result, many memory experiments have been criticized for having low ecological validity.
Matlin, M. W. (2005). Cognition. Crawfordsville: John Wiley & Sons, Inc.
Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63 (2): 81–97.
Sternberg, R. J. (1999). Cognitive psychology (2 nd ed.). Fort Worth, TX: Harcourt Brace College Publishers.
How to reference this article:
McLeod, S. A. (2007). Stages of memory - encoding storage and retrieval. Retrieved from www.simplypsychology.org/memory.html
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- For the journal of the same name, see Memory (journal)
Memory is the ability of the brain to store, retain, and subsequently recall information. Although traditional studies of memory began in the realms of philosophy, the late nineteenth and early twentieth century put memory within the paradigms of cognitive psychology. In the recent decades, it has become one of the principal pillars of a new branch of science that represents a marriage between cognitive psychology and neuroscience, called cognitive neuroscience.
There are several ways of classifying memories, based on duration, nature and retrieval of information. From an information processing perspective there are three main stages in the formation and retrieval of memory:
- Encoding (processing and combining of received information)
- Storage (creation of a permanent record of the encoded information)
- Retrieval/Recall (calling back the stored information in response to some cue for use in some process or activity)
Classification by durationEdit
A basic and generally accepted classification of memory is based on the duration of memory retention, and identifies three distinct types of memory: sensory memory, short-term memory, and long-term memory.
The sensory memory corresponds approximately to the initial moment that an item is perceived. Some of this information in the sensory area proceeds to the sensory store, which is referred to as short-term memory. Sensory memory is characterized by the duration of memory retention from milliseconds to seconds and short-term memory from seconds to minutes.
These stores are generally characterised as of strictly limited capacity and duration, whereas in general stored information can be retrieved in a period of time which ranges from days to years; this type of memory is called long-term memory.
It may be that short-term memory is supported by transient changes in neuronal communication, whereas long-term memories are maintained by more stable and permanent changes in neural structure that are dependent on protein synthesis. Some psychologists, however, argue that the distinction between long- and short-term memories is arbitrary, and is merely a reflection of differing levels of activation within a single store.
If we are given a random seven-digit number, we may remember it only for a few seconds and then forget (short-term memory). On the other hand, we can remember telephone numbers for many years (assuming we use them often enough). Those long-lasting memories are said to be stored in long-term memory.
Additionally, the term working memory is used to refer to the short-term store needed for certain mental tasks - it is not a synonym for short-term memory, since it is defined not in terms of duration, but rather in terms of purpose. Some theories consider working memory to be the combination of short-term memory and some attentional control. For instance, when we are asked to mentally multiply 45 by 4, we have to perform a series of simple calculations (additions and multiplications) to arrive at the final answer. The ability to store the information regarding the instructions and intermediate results is what is referred to as working memory.
Classification by information typeEdit
Long-term memory can be divided into declarative (explicit) and procedural (implicit) memories.
Declarative memory requires consciousrecall, in that some conscious process must call back the information. It is sometimes called explicit memory, since it consists of information that is explicitly stored and retrieved.
Declarative memory can be further sub-divided into semantic memory, which concerns facts taken independent of context; and episodic memory, which concerns information specific to a particular context, such as a time and place. Semantic memory allows the encoding of abstract knowledge about the world, such as "Paris is the capital of France". Episodic memory, on the other hand, is used for more personal memories, such as the sensations, emotions, and personal associations of a particular place or time. Autobiographical memory - memory for particular events within one's own life - is generally viewed as either equivalent to, or a subset of, episodic memory. Visual memory is part of memory preserving some characteristics of our senses pertaining to visual experience. We are able to place in memory information that resembles objects, places, animals or people in sort of a mental image. Visual memory can result in priming and it is assumed some kind of perceptual representational system or PRS underlies this phenomenon. 
In contrast, procedural memory (or implicit memory) is not based on the conscious recall of information, but on implicit learning. Procedural memory is primarily employed in learning motor skills and should be considered a subset of implicit memory. It is revealed when we do better in a given task due only to repetition - no new explicit memories have been formed, but we are unconsciously accessing aspects of those previous experiences. Procedural memory involved in motor learning depends on the cerebellum and basal ganglia.
So far, nobody has successfully been able to isolate the time dependence of these suggested memory structures.
Classification by temporal direction EditA further major way to distinguish different memory functions is whether the content to be remembered is in the past, retrospective memory, or whether the content is to be remembered in the future, prospective memory. Thus, retrospective memory as a category includes semantic memory and episodic/ autobiographical memory. In contrast, prospective memory is memory for future intentions, or remembering to remember (Winograd, 1988). Prospective memory can be further broken down into event- and time-based prospective remembering. Time-based prospective memories are triggered by a time-cue, such as going to the doctor (action) at 4pm (cue). Event-based prospective memories are intentions triggered by cues, such as remembering to post a letter (action) after seeing a mailbox (cue). Cues do not need to be related to the action (as the mailbox example is), and lists, sticky-notes, knotted hankerchiefs, or string around the finger (see box) are all examples of cues that are produced by people as a strategy to enhance prospective memory.
Overall, the mechanisms of memory are not well understood. Brain areas such as the hippocampus, the amygdala, or the mammillary bodies are thought to be involved in certain kinds of memory. For example, the hippocampus is believed to be involved in spatial learning and declarative learning. Damage to certain areas in patients and animal models and subsequent memory deficits is a primary source of information. However, rather than implicating a specific area, it could be that damage to adjacent areas, or to a pathway traveling through the area is actually responsible for the observed deficit. Further, it is not sufficient to describe memory, and its counterpart, learning, as solely dependent on specific brain regions. Learning and memory are attributed to changes in neuronal synapses, thought to be mediated by long-term potentiation and long-term depression.
- Main article: Neurophysiology of memory
Development of memoryEdit
As humans develop and mature their capacity for memory changes.
- Main article: Development of memory in childhood
- Main article: Aging and memory
Much of the current knowledge of memory has come from studying memory disorders. Loss of memory is known as amnesia. There are many sorts of amnesia, and by studying their different forms, it has become possible to observe apparent defects in individual sub-systems of the brain's memory systems, and thus hypothesize their function in the normally working brain. Other neurological disorders such as Alzheimer's disease can also affect memory and cognition.
Memorization, or rote learning, is a method of learning that conditions an individual to recall important information verbatim. This method of learning involves repetition, with the assumption that an individual can learn a necessary process or an amount of information through repetitive action or study, such to the point that it becomes near-automatic.
- Main article: Emotion and Memory
Hightened emotions can lead to experiences crystalizing into long-lasting and vivid memories. The Flash back's of Post traumatic stress disorder are one example of this. This boost in memory formation is partly due to the effects of the stress hormone norepinephrine. It appears that the hormone effects a receptor molecule called glautamate receptor 1 (GluR1) on nerve cell surfaces. The action appears to to be that Norepinephrine (a form of adrenaline triggers the attachment of a phosphate grroup to GluR1 and that this added phosphate group expedites the movement of GluR1 molecules to the surface, where they help cells form memories.
References & BibliographyEdit
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- "Memory is but the storage of fragmentary but 'relevant' features" - Walter J. Ong
- "It's a poor sort of memory that only works backwards" - Through the Looking-Glass by Lewis Carroll, Ch. 5, Wool and Water.
- "The existence of writing changed the nature of memory" - Jennifer Wise, in Dionysus Writes: The Invention of Theatre in Ancient Greece, 1998, p.25
- "The language of the Homeric epic exhibits a 'formulaic' linguistic style [to aid the memory]" - Jennifer Wise, in Dionysus Writes: The Invention of Theatre in Ancient Greece, 1998, p.27
- "I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skilful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it - there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones." A Study In Scarlet by Sir Arthur Conan Doyle, Ch. 2, The science of Deduction