The Multi-Store Model of Memory
The Multi-Store Model of Memory
Atkinson and Shiffrin (1968) proposed a model suggesting that our memory consists of three distinct components: the sensory register, short-term memory, and long-term memory, collectively termed the multi-store model of memory.
Each segment of this memory model is responsible for storing information. It’s essential to examine how information is encoded in each store, as well as the duration and capacity of each.
The Sensory Register (SR)
Coding
Information in the sensory register is coded based on our senses. Two stores include the iconic store, handling visual information, and echoic, processing auditory information. Additionally, we have the haptic, gustatory, and olfactory stores, responsible for tactile, taste, and smell sensations, respectively.
Capacity
Duration
We constantly process information from our surroundings, but unless we actively pay attention to it, it quickly fades away through spontaneous decay. The duration of the sensory register is described as very short, although it varies between different sensory stores.
Short Term Memory (STM)
Coding
The short-term memory (STM) is typically coded acoustically, primarily dealing with auditory information.
Capacity
The capacity of short-term memory (STM) is limited to approximately 5-9 pieces of information. However, this capacity can be extended through strategies like chunking, which involves grouping individual pieces of information into larger units, such as organizing letters into words or numbers into sequences.
Duration
The short-term memory (STM) can retain information for approximately 18 to 30 seconds before it is lost. However, through maintenance rehearsal, this information can be transferred and stored in the long-term memory (LTM) for more extended retention.
Long Term Memory (LTM)
Coding
The long-term memory (LTM) is typically coded semantically, dealing with information that has meaning.
Capacity
Duration
Although information in long-term memory (LTM) can be forgotten through decay or displacement, its potential duration is vast, often lasting a lifetime. Therefore, we characterize its duration as essentially indefinite.
Supporting Evidence
Sperling
Sperling (1960) conducted an experiment to explore the capacity of the sensory register (SR). Participants were presented with a 3 by 4 grid of letters, which flashed on the screen for 1/20th of a second. They were then tasked with recalling either the entire grid or a specific row indicated by a high, medium, or low-pitched tone.
When participants attempted to recall the entire grid, they correctly remembered approximately 4 out of 5 letters. However, when asked to recall a specific row, they could recall an average of three letters. These findings suggest that the sensory register likely retains all the information it is presented with, supporting its high capacity for sensory input.
Baddeley
Baddeley (1966) conducted an experiment where participants were presented with four groups of words and asked to recall them immediately to test their short-term memory (STM). They were then asked to recall the words again 20 minutes later to assess their long-term memory (LTM).
The word groups were as follows:
- Acoustically similar (e.g. Cat, Cab, Can)
- Acoustically dissimilar (e.g. Pit, Few, Cow)
- Semantically similar (e.g. Big, tall, large)
- Semantically dissimilar (e.g. Good, Huge, Root)
Participants encountered difficulty recalling group 1 immediately and group 3 after the 20-minute delay. Baddeley suggested that this difficulty stemmed from how the information was encoded in specific memory stores, leading to challenges in processing. Therefore, he proposed that short-term memory (STM) primarily encodes information acoustically, while long-term memory (LTM) encodes it semantically.
Jacobs
Jacobs (1887) conducted an experiment where participants listened to a series of either numbers or letters and immediately recalled them. If they were successful, the experiment continued with an increased number of letters or numbers until recall was unsuccessful. The average length of numbers recalled was 9.3, and for letters, it was 7.3. From these findings, Jacobs concluded that the capacity of short-term memory (STM) was around 5 plus or minus 2 pieces of information.
Building upon Jacobs’ work, Miller (1956) proposed that information could be grouped together, or chunked, to enhance memory capacity. He suggested that the capacity of STM is around 5 plus or minus 2 “chunks” of information, rather than individual pieces.
Peterson and Peterson
In 1959, this married couple designed an experiment to explore the duration of our short-term memory (STM). Participants were instructed to recall a nonsense trigram, a sequence of three consonants, to eliminate any potential interference from recognisable words e.g. FWZ.
Additionally, participants were given a 3-digit number and asked to count down in threes aloud from that number. After a delay of 3 seconds, they were prompted to recall the trigram. This process was repeated multiple times with increasing 3-second intervals.
The researchers observed that participants could correctly recall the trigram after 3 seconds approximately 80% of the time, but this ability decreased significantly after 18 seconds. From these findings, they concluded that the duration of STM was up to 30 seconds.
Bahrick et al
In 1975, Bahrick et al. conducted a study where a group of participants was asked to freely recall the names of their ex-classmates and also underwent a name or photo recognition test. Within 15 years of leaving school, 90% of participants correctly identified names and/or faces, with a 60% success rate for free recall. This free recall success rate decreased to 30% after an extended period.
However, even after 48 years, there was still an 80% success rate for recalling names and 40% for photos. These findings suggest that levels of recall remain relatively high over time, regardless of the recall method employed. Therefore, this supports the notion that the duration of long-term memory (LTM) can span a lifetime, barring any cognitive disorders that may affect memory retention.
Limitations
While the MSM has been supported by numerous experiments, its ecological validity is often called into question due to the artificial nature of many laboratory experiments. Indeed, the tasks used in such experiments, like recalling random letters or digits, may not accurately reflect real-life memory processes, such as recalling mobile numbers or shopping lists.
Moreover, the methodology of earlier experiments, such as Jacobs’s study conducted in the 1800s, may not meet contemporary standards of scientific rigor. Therefore, it’s essential to approach these findings with a critical eye and consider the potential limitations of the methodologies employed.
Additionally, the MSM provides a simplified explanation of memory processes and may not fully capture the complexity of human memory. For instance, in the context of memory-related diseases, such as Alzheimer’s, it’s evident that memory involves more than just a single short-term and long-term memory store. There’s evidence to suggest the existence of different types of long-term memory, and models like the Working Memory Model offer a more detailed understanding of short-term memory processes.
Overall, while the MSM has provided a valuable framework for understanding memory, it’s crucial to recognize its limitations and consider alternative models and perspectives to gain a comprehensive understanding of human memory.