Memory

• Cognitive psychology


  Deals with internal mental processes such as thought, language, perception, emotion and memory
• Computer metaphor


  The idea that the mind is like a computer, which inspired the work of cognitive psychologists
• Cognitive psychologists


  • Develop theories and models about different aspects of mental function, and test these using laboratory experiments
• Laboratory experiments


  • Very well-controlled and scientific, allowing determination of cause-and-effect relationships
• Laboratory experiments


  • Tasks are often very artificial and have limited relevance to real life, so ecological validity is limited
• Memory


  The process of retaining information for some time after it is learned
• Stages of memory


  • Encoding
  • Storage
  • Retrieval

  
• Encoding


  Translating information into a form the brain can use, the first stage of memory
• Storage


  Encoded memories must be stored somewhere in the brain

  
• Retrieval


  There must be some way of accessing stored memories
• Multi-store model of memory (MSM)

  Information to be remembered flows through a series of three stores: sensory register, short-term memory, and long-term memory

  
• Stores in the MSM

  • Sensory register
  • Short-term memory
  • Long-term memory

  
• Stores in the MSM

  • Differ in terms of their coding, capacity and duration
• Coding


  The format in which information is stored
• Capacity


  The amount of information that can be held in each store
• Duration


  The length of time that information can be retained in each store
• Coding in short-term and long-term memory

  1. Baddeley (1966) study

  2. Participants recalled acoustically-similar or semantically-similar words in short-term or long-term memory conditions

  3. Acoustic coding in STM, semantic coding in LTM

  
• Coding in sensory register

  • Depends on the sense organ, as the code is a representation of the physical properties of the stimulus (iconic, echoic, haptic)
• Capacity in short-term memory

  1. Jacobs (1886) study

  2. Participants recalled lists of numbers or letters until 50% accuracy

  3. Immediate digit span ~9, letter span ~7, capacity increases with age

  
• Capacity of short-term memory

  • Limited to between 5 and 9 items, numbers easier to recall than letters
• Capacity in long-term memory

  1. Luria (1964) study of mnemonists

  2. LTM capacity seems practically unlimited

  
• Duration in short-term memory

  1. Peterson and Peterson (1959) study

  2. Participants recalled consonant trigrams after intervals of 3-18 seconds with no rehearsal

  3. 80% correct after 3 seconds, less than 10% after 18 seconds
• Duration of short-term memory

  • Very short (around 20 seconds) without rehearsal, information lost through decay
• Duration in long-term memory

  1. Bahrick et al. (1975) study

  2. Participants recognised or recalled high school classmates after 7-47 years

  3. Recognition better than recall, some memories last a lifetime
• Duration of long-term memory


  • Can last a lifetime, recognition easier than recall
• Capacity and duration in sensory register

  1. Sperling (1960) study

  2. Participants shown 3x4 grid of letters/numbers for less than 1/20 second

  3. Capacity at least 10 items, but duration less than 2 seconds
• Multi-store model (Atkinson and Shiffrin)

  Cognitive model describing how memory passes through sensory register, short-term memory, and long-term memory

  
• Processes in the multi-store model

  • Physical stimuli received in sensory register
  • Attended information passes to short-term memory, rest decays
  • Maintenance rehearsal keeps information active in short-term memory
  • Elaborative rehearsal transfers information to long-term memory
  • Retrieval brings memories from long-term to short-term memory

  
• Stores in the multi-store model

  • Differ in coding, capacity, and duration as described previously
• Episodic memory


  Autobiographical memory, enables re-experiencing past events, prone to errors and illusions, declarative/explicit
• Semantic memory


  Memory for facts and knowledge, another form of declarative memory

  
• Case study of amnesic patient KC demonstrates distinction between episodic and semantic memory
• Procedural memory


  Memory for physical skills and learned behaviors, resides in the cerebellum, implicit

  
• Amnesic patient HM could learn new procedural memories despite having no conscious recollection of learning them
• Working memory model (WMM)

  Model of short-term memory with multiple active components, interacting with long-term memory, all with limited capacity

  
• Components of the WMM

  • Central executive controls information processing, phonological loop and visuo-spatial sketchpad process auditory and visual information respectively

  
• The amnesic patient HM (first studied by Brenda Milner) was able to learn new procedural memories, whilst having no conscious recollection of learning them
• HM was able to trace the outline of a star in a mirror (a difficult motor task) with practice, but had no recollection of having done it before
• Working Memory Model (WMM)

  A model of short-term memory where the components are active, not just stores like in the Multi-Store Model

  
• Components of the Working Memory Model

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