Multi-Store Model of Memory

The three main stores are sensory register (SR), short-term memory (STM) and long-term memory (LTM).

Memory is formed sequentially, and information passes from one store component in the model to the next in a fixed and linear order.

They are 1) encoding, 2) capacity, 3) duration.

When attention is paid to something in the environment, it is then converted to short-term memory (STM).

Maintenance rehearsal is repeated to keep information in STM.

Prolonged rehearsal (a long period of rehearsal) will create long-term memory (LTM).

If rehearsal does not occur, information will be forgotten and lost from STM through the processes of displacement or decay.

The sensory register (SR) has a larger capacity, which includes all sensory experiences. The duration is short, typically within ¼ to ½ seconds. The encoding process is sensory-specific, which means there are different stores for each sense.

Short-term memory (STM) capacity holds around 7 +/- 2 items. The duration lasts about 0-18 seconds. The encoding method is mainly acoustic.

Long-term memory (LTM) is proposed to have unlimited capacity. The duration lasts for a lifetime. The encoding method is mainly semantic.

Cohen and Squire (1980) added two further types of LTM: explicit memory and implicit memory.

Explicit memory, also known as declarative memory, involves conscious effort to be stored and recalled. For example, knowledge about the world and personal events.

Implicit memory, also known as procedural memory, does not involve conscious effort to be stored and recalled. For example, skills and action.

Explicit Memory can be subdivided into semantic memory and episodic memory.

Procedural memory is the memory of skills and behaviours, stored in the form of motor actions and formed with time stamps.

Research evidence from Baddeley (1966) supports the idea of LTM and STM being different and separate stores. In his study on coding, he gave participants one of four lists of words to remember. He found that acoustically similar words were harder to recall immediately, and semantically similar words were harder to recall 20 minutes after the test. It was concluded that acoustic confusion occurred in STM and semantic confusion in LTM, suggesting STM codes acoustically and LTM semantically.

Glanzer and Cunitz (1966) supported the existence of separate LTM and STM stores because they observed a primacy and recency effect. This research provided evidence for the MSM: people tend to remember the first items because they have more time to rehearse the information, and they may have paid more attention to it. Therefore, these items have a higher probability of being transferred to the LTM. The participants also tended to remember the most recent information because those were still in their STS. Information in the middle might have been lost because of the limited capacity of the STM.

HM had significant long-term memory impairment as a result of brain surgery. He had little memory of personal (mother and father's deaths) or public events (Watergate, Vietnam War) that had occurred in the last 45 years. Yet, his short-term memory was unaffected. This resonated with the idea in MSM that HM fails to rehearse information from STM to LTM and further supported the idea of the separate stores for STM and LTM.

The Working Model of Memory proposed by Baddeley and Hitch (1974) is based on the MSM.

The MSM argues that STM is a unitary store (i.e. there is only one type). However, evidence from patients suffering from amnesia suggests that this is not true. KF's STM for digits was very poor when others read the numbers to him. On the other hand, his recall was much better when he could read the digits to himself. This suggests that there is more than one STM store (one for sounds and one for images). This case challenges the MSM as it shows that there must be at least two types of STM, rather than just one unitary store as the model suggests.

The Working Memory Model (Baddeley and Hitch, 1974) suggested that we can recall information that we did not rehearse. However, in some cases, we cannot recall information that we have rehearsed. Therefore, the Working Memory Model denies the importance of rehearsal for transferring from STM to LTM proposed in MSM.

Craik and Watkins (1973) argued that the maintenance rehearsal (repetition to help us hold information in the STM) is not the only type. They proposed one more type of rehearsal, which is the elaborative rehearsal. Maintenance rehearsal is a shallow process that helps you retain information in the STM. Elaborative rehearsal is a deep process that links information to your existing knowledge. The deeper the processing, the more memorable the information becomes. In other words, a long period of maintenance rehearsal cannot move information from STM to LTM. LTM can be formed only if Elaborative rehearsal occurs. The findings of Craik and Watkins (1973) contradicted MSM, as evidence showed that forming LTM involves more than maintenance rehearsal.

Despite a few research that support the MSM, many studies used artificial tasks in their testing. This raises the concern of evidence lacking ecological validity. The testing is typically based on lab experiments involving tasks like the Brown-Peterson Technique. These are artificial, often involving meaningless trigrams. However, in everyday life, we form memories related to all sorts of useful information. Yet, many of the studies that support the MSM use none of these real-life materials. This means that the MSM may not be an accurate or valid model of how memory works in our daily lives.

The short-term memory definition is information with limited capacity and available for a limited time.

Information is acoustically encoded in the short-term memory store.

Peterson & Peterson (1956).

The duration of short-term memory is about 15-30 seconds.

Peterson & Peterson (1959) found 80% memory recall accuracy after 3 seconds, 50% after 6 seconds and 10% after 18 seconds. This finding suggests the duration of short.term memory store to be 18 seconds. 

Miller (1956) proposed the 7+/-2 theory, suggesting the short-term memory store’s capacity to be between five and nine ‘blocks’ of information.

Conrad (1964).

In the study, participants recalled a series of digits/letters. The sequence of letters and numbers was gradually increased throughout the experiment. The results showed that participants could recall an average of 7.3 letters and 9.3 digits (suggesting participants were better at remembering numbers).

The purpose of distraction tasks is to prevent memories from being moved to the long-term memory store. If this occurs, then the research findings would have low validity.

To ensure the memories measured are from the short-term memory store. 

Recall accuracy declines the longer the information is stored in the short-term store. Once the store reaches its duration and capacity limitation, the information is displaced or decays.

Peterson and Peterson (1959) presented participants with trigrams and gave them a distraction task to prevent rehearsal of the stimuli. The purpose of the distraction task was to prevent the information from being moved and processed in the long-term memory store.

The short-term and long-term memory stores differ in terms of encoding methods, duration, and capacity of holding information.

How information is processed/coded and stored.

Information can be encoded acoustically by repeatedly saying the information out loud.

Memory decay is when information is forgotten because the store has reached its limit for holding the memory. It occurs due to the memory not being rehearsed enough and moved to the long-term memory store. 

Memory displacement refers to information being replaced with new information because the store has reached its capacity. 

Peterson and Peterson (1959) aimed to investigate the duration of short-term memory.

Acquired, stored, retained and retrieved.

Peterson and Peterson (1959) used trigrams, these are combinations of three letters that are not real words.

Encoding, duration and capacity.

Yes, to avoid rehearsal Peterson and Peterson (1959) asked participants to do a mental math exercise.

They found that the shorter the interval between learning and recall was, the better the performance. After 3 seconds, around 80% of the trigrams were recalled, while after 18 seconds, only 10% were recalled. This was taken as evidence that the duration of this type of memory is of around 18 seconds, which can be described as short. 

Long-term and short-term memory.

Semi-permanent.

False.

It refers to the amount of information that can be stored.