The Multi-store Memory Model
The Multi-store Memory Model
Atkinson and Shiffrin where the two psychologists who explained how our memory works by ‘The Multi-store Memory Model ‘. This model suggest that our mind has 3 different storage system:
1. Sensory memory
2. Short term memory
3. Long term memory
These three memories are different in term of 4 key features:
1. Capacity
2. Duration
3. Encoding
4. Reason for forgetting
Sensory memory is the shortest-term element of memory. It acts as a kind of buffer for stimuli received through the five senses of sight, hearing, smell, taste and touch, which are remembered accurately, but very briefly. For example, the ability to look at something and remember what it looked like with just a second of observation is an example of sensory memory. It has a very large capacity however, the visuals can only stay for 1/10 second and auditory or 2 seconds. It lasts for such a short time that it is often considered part of the process of perception, but it nevertheless represents an essential step for storing information in short-term memory. Sensory memory decays or damages very quickly, which is the reason why we forget.
Short term memory has three significant aspects: capacity, duration and encoding. Miller’s (1956) Magic number 7 provides evidence for the capacity of short term memory. Most adults can store between 5 and 9 items in their short-term memory. This idea was put forward by Miller (1956) and he called it the magic number 7. He though that short term memory could hold 7 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.
Miller’s theory is supported by evidence from various studies by other psychologists such as Jacobs (1887).
He used the digit span test with every letter in the alphabet and numbers apart from “w” and “7” because they had two syllables. He found out that people find it easier to recall numbers rather than letters. The duration of short term memory seems to be between 15 and 30 seconds, according to Atkinson and Shiffrin (1971).
Items can be kept in short term memory by repeating them verbally (acoustic encoding), a process known as rehearsal.
Using a technique called the Peterson technique which prevents the possibility of retrieval by having participants count backwards in 3s, Peterson and Peterson (1959) showed that the longer the delay, the less information is recalled. The rapid loss of information from memory when rehearsal is prevented is taken as an indication of short term memory having a limited duration and this also results in us forgetting. Other researchers such as Sebrechts et al. (1989) did an experiment where participants recalled 3 stimulus words well if tested immediately, but recall was almost zero after 4 seconds. This supports the notion that STM has a very limited duration when data is not released.
In 1974 another experiment was carried out by Rietman where concentration of participants disturbed, recall of 5 words after 15 sec drops by 24% which again supports the concept that with no rehearsal information disappears.
Long term memory: it seems likely that long-term memory actually decays very little over time, and can store a seemingly unlimited amount of information almost indefinitely. One of the earliest and most influential distinctions of long term memory was projected by Tulving (1972).
He proposed a distinction between episodic, semantic and procedural memory.
Episodic memory refers to our ability to recall personal experiences from our past. When we recount events that happened during our childhood or what we ate for breakfast, we are employing our long-term episodic memory. As its name suggests, this aspect of memory organizes information around episodes in our lives. When we try to recall the information, we attempt to reconstruct these episodes by picturing the events in our minds. Episodic memory enables us to recall not only events, but also information related to those events.
Semantic memory stores facts and generalized information. It contains verbal information, concepts, rules, principles, and problem-solving skills. While episodic memory stores information as images, semantic memory stores information in networks. Information is most easily stored in semantic memory when it is meaningful – that is, easily related to existing, well-established plans.
Procedural memory refers to the ability to remember how to perform a task or to employ a strategy. The steps in various procedures are apparently stored in a series of steps, or stimulus-response pairings. When we retrieve information from procedural memory, we retrieve one step, which triggers the next, which triggers the next, etc.
A lot of experiments has been done by psychologists about the long term memory for instance, Bahrick et al (1975) investigated what they called very long term memory (VLTM).
Nearly 400 participants aged 17 – 74 were tested. There were various tests including: A free recall test, where participants tried to remember names of people in a graduate class. A photo recognition test, consisting of 50 pictures. Results of the study showed that participants who were tested within 15 years of graduation were about 90% accurate in identifying names and faces. After 48 years they were accurate 80% for verbal and 70% visual. Free recall was worse. After 15 years it was 60% and after 48 years it was 30% accurate. Which suggest that we recognise better than we recall, so information is always there even if we can’t access it and this is also why we forget in LTM. Long term memory relies more on the meaning. However, his work could be criticized as we don’t know how much these people had recalled about their classmates and mentioned them in conversation-this would have the effect of refreshing their memory.
Shepard a psychologist whose experiment showed that recognition memory is very good over long term, at least for memorable material.in his experiment participants could almost recognise almost 600 memorable pictures when views again after one hour and , and 40% after 4 months.
Some of our memories are enduring, possibly just those that are personally significant and this has been showed by an experiment that was carried by Waganaar and Groeneweg where concentration camp survivors had good recall for many but not all, details after 30 years.
Merkle also another psychologist found the capacity of our memory may be in range 10 to the power 13 – 10 to the power 15, calculations based on the number of synapses in the brain.
In conclusion Baddeley (1966) carried out two types of experiment: one for short term memory and on for long term memory. In short term memory experiment he put people into groups. Each group heard one list of words (acoustically similar or dissimilar, semantically similar and dissimilar).
This list was repeated 4 times; each time participants were shown a list of the words jumbled up and asked to recall them in correct order and the similar experiment was carried for long term memory as well except this time recall was after 20 minutes retention interval during which participants performed another task.
In STM he found out that people get confused on words that sound similar meaning STM is based on words/sounds. We call this acoustic encoding. Whereas, in LTM people got confused with words that had similar meaning which meant LTM uses semantic encoding where we remember the meaning of something.
However, The model is too simplistic. When considered more closely case studies of amnesiacs suggest that both STM and LTM are far more complex than the multi-store model suggests, e.g. Clive Wearing has an intact memory for skills but a severely impaired memory of facts. Clive has a severely weakened STM but his LTM is intact. According to the multi-store model this could not happen since the memories in LTM must pass through STM first.