Broadbendt (1971) suggested that memory works like an office worker that reviews and transfers information from an 'in basket' where incoming paperwork is placed temporarily on a desk (i.e. an analogy for STM). The important things are stored in a filing cabinet for longer (i.e. an analogy for LTM). Throughout psychology, psychologists have referred to the structures of memory with computer analogies.
But is it really how memory works? We'll explore the memory model that inspired these metaphors to answer this question.
- First, we'll look at the structure of memory definition by introducing the Multi-Store Memory Model.
- Next, we'll look into the structure of memory examples to identify the different types of memory structures.
- Then, we'll illustrate the structure and function of memory using a diagram.
- Moving along, we'll look at the stages of memory in psychology.
- Finally, we'll look at the evidence for the types of memory structure and outline the criticism of the model.
The Multi-Store Memory Model proposes that there are different memory stores in our brain, freepik.com
Structure of memory definition
Memory in psychology can be defined as a mental ability to encode, store and retrieve information. But why does some information stick, and some go in one ear and out of another?
Atkinson & Shiffrin (1968) proposed a model of memory that can account for the variability in memory processes. They posited that memory comprises several structures, each having its own characteristics.
The multi-store memory model conceptualises memory as interconnected stores that process and keep information.
Structure of memory examples
According to Multi-Store Memory Model, memory is not a unitary system. Instead, it consists of the sensory store, the short-term memory store (STM) and the long-term memory store (LTM).
Types of memory structure: Sensory store
The sensory store, also known as the sensory register, is where the sensory information from the environment is first processed. Everything we perceive through our senses at any given moment is filtered through this store.
The sensory register doesn't have a capacity limit, meaning it can store an unlimited number of sensory stimuli. Still, the duration for which information can stay there is very short. After a fraction of a second, the information is either transferred to the short-term memory store or is forgotten.
For the transfer to occur, we need to pay attention to the information. Only the information that is attended to can move to the STM store.
If a friend is talking to you while you're paying attention to your phone, you won't remember what they said even a second later because you weren't paying attention.
Types of memory structure: Short-Term Memory Store
The short-term memory store can hold information for around 18 seconds, but its capacity is limited to only about 7 (+/- 2) chunks of information. For information to enter this store, it needs to be encoded acoustically or in the form of words; this can occur through verbal or mental repetition.
When information is held in the STM, it is readily available for us to recall, we can also rehearse the information in our mind, so it stays in our memory for longer. This is called maintenance rehearsal.
Moreover, rehearsal allows the transfer of information to the long-term memory store. The information not sufficiently rehearsed is forgotten either because the store has reached its limited duration making (decay) or because of displacement. Displacement occurs when old information is replaced by new information.
When we are trying to learn new information, we rehearse it over and over. Think of a time when you were learning lines for a performance, or a time when you were trying to remember a new phone number. You may say them in your head repeatedly (acoustic encoding), and sufficient rehearsal can lead to the memory moving to the long-term store, where it's available for a longer time.
Types of memory structure: Long-Term Memory Store
The memories we make throughout our lifetime are stored in the long-term memory store. Its capacity is thought to be unlimited, similarly to its duration. Encoding of information occurs semantically, which means information is stored based on its meaning. For the information to be transferred to our long-term memory, elaborative rehearsal is necessary.
Elaborative rehearsal involves repeatedly attending to new information to give it a rich meaning that can be encoded and stored in LTM.
Once the information is stored in the long-term store, we can bring it back to awareness, reminisce and think about it. However, as time passes, some memories will decay and be forgotten.
When you first learn about the multi-store memory model, it might not mean much to you. But once you connect the concepts of STM and LTM with your personal experiences of forgetting, you can effectively store this knowledge in your long-term memory because it has meaning to you.
In 2019 Kim Surim memorised 2,530 playing cards put in random order. How did he manage to encode all this abstract information? Memory champions use elaborative rehearsal to their advantage. Instead of repeating Queen of clubs, 6 of diamonds, 3 of spades and so on, they create elaborative stories that add meaning to this information. For example, a courageous queen used clubs to protect her six unique diamonds against three thieves with spades.
Structure and function of memory
The diagram illustrates how information flows through the stores in the multi-store memory model.
The multi-store model of memory diagram, StudySmarter Originals
Stages of memory in Psychology: encoding, duration and capacity
Let's summarise how different memory stores encode information, how long they can store information and how much information they can contain.
Encoding refers to the process through which information is converted in a way that can be stored by the structure. Duration refers to the period of time that the information is held in the store before it is forgotten. In contrast, capacity refers to the amount of information that the store can hold.
| Memory structure | Sensory Register | Short-Term Memory | Long-Term Memory |
| Encoding | Sensory input | Acoustically | Semantically (meaning) |
| Capacity | Unlimited | 7 +/- 2 chunks of information | Unlimited |
| Duration | Fraction of a second (0.25-0.5 second) | 18 seconds | Unlimited |
Evidence for the types of memory structure
There are several experimental research findings that are consistent with what Atkinson and Shiffrin (1968) predicted in their model.
Murdock's serial position curve study
Murdock (1962) presented 16 participants with lists of random English words. His lists varied in length, with the shortest having ten and the longest having 40 words. By the end of the list, participants were asked to write down all the words from the list that they could remember.
It was found that participants remembered the words at the beginning (primacy effect) and the end of the list the best (recency effect), while the words in the middle weren't remembered as well. This is called the serial position effect.
The Serial position effect refers to the finding that the memory of words depends on their position on the list.
The study concluded that the primacy effect is likely due to participants having time to rehearse, so they moved to LTM. And the recency effect was due to the information not yet decaying from the STM store at the time of recall.
Murdock's findings support the existence of separate memory stores, one which keeps rehearsed information and one which keeps the recent information for a brief period.
Peterson & Peterson (1959) short-term retention study
Peterson & Peterson (1959) investigated the duration for which information can be kept in the short-term memory store when maintenance rehearsal is controlled.
They presented participants with a list of trigrams – combinations of three random consonants (e.g., WQB). Participants had to count back from a random number after seeing the list; this is a form of distraction task to prevent recall.
Researchers found that the number of trigrams that participants remembers decreased with time.
- After six seconds without rehearsal, participants only remembered 50% of trigrams, while after 18 seconds they remembered less than 10%.
It was concluded that the information in short-term memory decays after around 18 seconds.
The case study of Clive Wearing
The case of Clive Wearing was described by Wilson, Kopelman and Kapur (2008). Clive Wearing was a patient who developed global amnesia after a viral infection. He lost the ability to create new memories and forgot all the information stored in his long-term memory.
Wearing could still keep information in his short-term memory for a brief time but then would forget what had just happened after a few seconds had passed.
Clive's STM memory was preserved despite the neurological damage that caused LTM loss. His case suggests that STM and LTM rely on different memory stores, which supports the Multi-Store Memory Model.
Before he contracted the viral infection, Clive Wearing was a musician. Interestingly, even after losing all his memories, he still remembered how to play the piano, suggesting LTM might not be as unitary as the Multi-Store Model proposes.
Memory case studies such as that of Clive Wearing provide supporting evidence of the multi-store model of memory, freepik.com
Criticism of the Multi-Store Memory Model
Some aspects of the Multi-Store Model have been criticised. The capacity of short-term memory can differ depending on the person. Some people struggle to keep the seven chunks of information in their memory, while others can remember a few more. Therefore, it doesn't account for individual differences.
Alternative memory models have also proposed that the STM store does more than just storing and rehearsing. It is also thought to be capable of manipulating information to aid complex processes like problem-solving, reasoning, or planning.
Some critics argue that rehearsal is not always sufficient or necessary for the transfer of information. Some events from our past can be recalled for a long time despite not rehearsing them. On the other hand, sometimes we rehearse information, for example, to prepare for a test, and we still have problems recalling it later, suggesting the model may be too simplistic.
Evidence also suggests that the LTM store proposed by this model is oversimplified and that there are likely many types of long-term memories that are stored differently. This is exemplified by the case of Clive Wearing, who, despite losing his long-term autobiographical memory, retained his long-term procedural memory.
Structures of Memory - Key takeaways
- The Multi-Store Memory Model was proposed by Atkinson & Shiffrin (1968). The model argues there are three separate memory stores: sensory register, short-term memory store and long-term memory store.
- The sensory register encodes information in the form of sensory stimuli, and has unlimited capacity but can only hold the information for a fraction of a second. Information can be transferred from the sensory register to the STM store through attention.
- The STM store encodes information acoustically, it has a limited capacity and only holds information for about 18 seconds. After that time, the information is either transferred to the long-term memory store through rehearsal or is forgotten.
- The LTM store encodes information semantically. Its capacity and duration are unlimited. Once the information is in the LTM store, we can recall it, but over time it can still decay and become forgotten.
- The Multi-Store Memory Model is supported by several studies, including Murdock's serial position curve study, Peterson & Peterson's (1959) study and the case study of Clive Wearing. However, it has been criticised for being over-simplistic.
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