Memory

• Multi-store model of memory

  Sensory register, short-term memory and long-term memory

  
• Always draw out diagrams of memory models if you have time as this gains you credit
• The Multi-Store Model of Memory

  Devised by Atkinson and Shiffrin in 1968

  
• This theoretical model seeks to explain how information is transmitted from the outside world through different stores memory, and how it is processed at each point

  
• Features of each store

  • Coding
  • Capacity
  • Duration
  • Function
• Coding


  The format the information is stored in
• Capacity


  How much (the quantity) of information that can be held in the memory store at any one time
• Duration


  How long information stays in the memory store
• Function


  What each store does
• The mind is flooded with environmental stimuli coming from the eyes, ears, taste receptors, touch receptors ..etc.
• Sensory Register


  The information enters and is coded in the sensory register in whatever form it was perceived in (so it is modality specific) and each kind is stored in a different store within the sensory register depending on which sense organ the information came from
• Sensory memory stores


  • Iconic store (visual)
  • Echoic store (sound)
  • Olfactory store (smell)
  • Haptic store (touch)
  • Gustatory store (taste)

  
• Duration of sensory memory

  Only about 250 milliseconds
• Only sensory information that we pay attention to will move to the next store, and so the vast majority will be lost
• Short Term Memory


  Duration of about 18-30 seconds
• Rehearsal


  • Maintenance rehearsal keeps the information in the short term memory for longer, and it may pass into the long term memory eventually
  • Elaborative rehearsal is where we semantically encode the information (give it meaning), moving it directly from the short term memory to the long term memory
• Chunking


  A way to improve short term memory by grouping items so that each group is treated as one item by the short term memory, thus improving recall as the overall number of 'items' is reduced
• Long Term Memory


  • Information has an unlimited duration and it has an unlimited capacity
  • Information may be lost (we lose access to it), but this may be regained at a later date
  • Information is coded semantically (based on its meaning)
  • To use the information in the long term memory we need to bring it out of the long term memory and back into the short term memory. This process is called retrieval
• Unlike the short and long term memory the sensory register is not under conscious control; it is recorded automatically. Any information found in the short or long term memory is initially gathered by the sensory register

  
• Sperling (1960) flashed a grid of 20 letters onto a screen for a 20th of a second. When participants were asked to recall random rows of letters the recall was strong. This suggests that all the rows of letters were stored in the sensory register as participants didn't know which row would be asked for, meaning that the iconic store in the sensory register has a large capacity

  
• Baddeley (1966) gave four 10 word lists to four participant groups. The first list consisted of acoustically similar words (words that sound similar). The second list consisted of acoustically dissimilar words (words that sound different). The third list consisted of semantically similar words (words with similar meanings), and the fourth list consisted of semantically dissimilar words (words with unrelated meanings). Baddeley found that immediate recall was worst for list 1, and recall after 20 minutes was worst for list 3. This suggests that information in the short term memory is coded acoustically
• Jacobs (1887) presented participants with a list of letters or numbers. Participants then had to recall the list in order. Jacobs found that the capacity for letters was around 7 items and 9 for numbers, suggesting that the capacity of the short term memory is very limited
• Peterson and Peterson (1959) showed participants 3-letter trigrams (i.e: HFR, TKD). Trigrams with any meaning were avoided so that participants could not rehearse the information semantically. Then participants had to count backwards for a few seconds. This interference task was designed to stop maintenance rehearsal. Peterson and Peterson found that after 18 seconds recall was less than 10%. This suggests that information remains in the short term memory for only a few seconds before it disappears
• Baddeley (1966) (see above)
• Wagnaar (1986) kept a diary over the course of six years which recorded over 2,400 events. He tested himself on the events and found a 75% recall after 1 year and a 45% recall after 5 years, suggesting that the capacity of the long term memory is very large, potentially limitless
• Bahrick (1975) showed old photographs and names (including those of old school friends) to participants aged 17-74, recall was 90% after 15 years, and still 80% for names after 48 years. This suggests that the duration of the LTM is very large, potentially limitless
• Evaluation of the Multi-store Model

  • The short duration of the SR is supported by evolutionary theory, as in the wild quick reactions are vital for survival, so only important information would be retained and processed. Too much information would lead to slower reactions.
  • There is a large base of research that supports the idea of distinct STM and LTM systems. An example of this is the Shallice and Warrington (1974) study of KF, a brain-damaged case study patient whose STM was impaired following a motorcycle accident, but his LTM remained intact.
  • It makes sense that memories in the LTM are encoded semantically – i.e. you might recall the general message put across in a political speech, rather than all of the words as they were heard.
  • The MSM was a pioneering model of memory that inspired further research and consequently other influential models, such as the Working Memory Model.
  • Some research into STM duration has low mundane realism, as the stimuli participants were asked to remember bear little resemblance to items learned in real life, e.g. Peterson and Peterson (1959) used nonsense trigrams such as 'XQF' to investigate STM duration. Similarly the ecological validity of many of the experiments is low as they were carried out in lab environments, so participant behaviour may not be the same as would be expected in a more natural environment. This can lead to low external validity for the findings.
  • The model is arguably over-simplified, as it sees each store as a single unit, but evidence suggests that there are multiple short and long-term memory stores, e.g. 'LTM' can be split into Episodic, Procedural and Semantic memory.
  • It does not make much sense to think of procedural memory (a type of LTM) as being encoded semantically, i.e. knowing how to ride a bike through its meaning.
  • The capacity of the STM can be significantly altered by factors such as age (reduces) and practice (increases). This means that the view of a fixed STM capacity is incorrect.
  • It is only assumed that LTM has an unlimited capacity, as research has been unable to measure this accurately
• Types of long-term memory

  • Declarative/Explicit (knowing what something is)
  • Nondeclarative/Implicit (knowing how something happens/is done)

  
• Types of Declarative/Explicit memory

  • Episodic memory
  • Semantic memory
• Episodic memory


  • A memory of experiences and specific events
  • Stored with reference to the time and place where they occurred
  • Recalled using conscious effort and can be expressed with words
  • Autobiographical and emotions felt at the time when the memory is encoded influences memory strength
  • Initially coded in the prefrontal cortex, and are then stored across areas of the brain, though recall seems to occur through the hippocampus
• Semantic memory


  • The memory of facts, meanings, and concepts
  • Require conscious effort to recall and can be expressed in words
  • Memories are stronger if processed more deeply (i.e: linked to other long term memories)
  • Last longer than episodic ones
  • May not recall when learned/encoded these memories
  • Episodic memories become semantic over time
  • Associated with the Perirhinal cortex
• Procedural memory


  • Unconscious memory of skills/how to do things
  • Examples are motor/muscle memories (i.e: how to ride a bike)
  • Often learnt in childhood
  • Hard to express in words or consider consciously
  • More resistant to forgetting than episodic or semantic
  • Located across the brain but particularly in the motor cortex, cerebellum, and prefrontal cortex
• Hertz (1997) found that females were better on episodic tasks, but there was no difference on semantic tasks. This difference in performance suggests that episodic and semantic memories are separate processes
• Vicari (2007) found deficiencies in CL's episodic LTM functions, especially in creating new episodic memories, but had no trouble creating or recalling semantic memories. Shows that semantic and episodic memories are separate and use different brain areas, as the area with the damage was the hippocampus, which was thought to be where her episodic memories were stored, but there was no damage to her perirhinal cortex were semantic memories thought to be stored
• Finke (2012) studied PM, a 68 year old cellist with brain damage after encephalitis. He had amnesia and it was found that his episodic and semantic memory were both very affected, but ability to play and read music unaffected, including learning new pieces, showing that his procedural LTM to be separate to his semantic and episodic
• Sacks (2007) Clive Wearing has retrograde amnesia so cannot remember his musical education (episodic), however remembers facts about his life (semantic). He can also play the piano (procedural). He is unable to encode new episodic or semantic memories due to the anteriorgrade amnesia, but under some experimental conditions is able to gain some new procedural memories through repetition. This shows that semantic, procedural, and episodic memories are all separate systems that are perhaps found in different brain areas
• Evaluation of types of long term memory

  • Using case studies such as Sack's study of Clive Wearing allows us to gain insights that would not be possible in an experimental setting, but lack enough control to suggest a cause and effect relationship between brain areas and memory functions. It could be that the people in these case studies are different to the normal population in some way even before their brain damage (i.e: Clive and PM are both musicians, which may have affected how their brain damage altered their behaviours. Similarly CL was a child, so perhaps her brain was more able to adapt than an adult brain would be).
  • The use of brain scanning in modern cognitive neuroscience has allowed researchers to study the brain and memory more scientifically, identifying the brain areas where different types of memory are located via which parts of the brain are activated when it is scanned via fMRI.
  • As both episodic and semantic memories are declarative there may not be a true division between them
• Working Memory Model


  • Created by Baddeley and Hitch in 1974
  • Meant to be a replacement for the Short-term Memory store
  • Initially had three components, but they added a fourth later

  
• Components of the Working Memory Model

  • Central Executive
  • Phonological loop
  • Visuo-spatial sketchpad
  • Episodic buffer

  
• Central Executive


  • The director/head of the model and receives and filters the information before passing it on to two 'slave' systems
  • Limited in capacity, so it can only hold one piece of information at a time
  • Switches attention between different inputs