Memory

• Multistore model of memory


  Atkinson and Shiffrin 1968, a theoretical cognitive model of how the memory system processes information
• Sensory register


  1. Receives raw sense impressions

  2. Attention passes info to short-term memory

  3. Coding is modality specific

  4. Capacity is very large

  5. Duration is very short (250 milliseconds)
• Short-term memory


  1. Receives info from sensory register by paying attention or from long-term memory by retrieval

  2. Keeps information by repeating maintenance rehearsal or passing to long-term memory

  3. Coding is acoustic

  4. Duration is approximately 18 seconds

  5. Capacity is 7 plus/minus 2 items
• Long-term memory


  1. Very long duration, permanent memory storage

  2. Theoretically unlimited capacity

  3. Forgotten information appears to be inaccessible

  4. Coded semantically in the form of meaning

  5. Must be passed back to short-term memory to use the information
• Recall of a random row of a 12x12 grid flashed for 120th of a second was 75%, suggesting all rows were stored in sensory register but quickly forgotten
• Immediate recall was worse for acoustically similar words and recall after 20 minutes was worse for semantically similar words, suggesting short-term memory is coded acoustically and long-term memory is coded semantically
• Capacity of short-term memory

  Average 7 items for letters, 9 for numbers (Jacobs)
• Duration of short-term memory

  Less than 10% recall of a 3-letter trigram after 18 seconds with an interference task (Peterson and Peterson)
• Capacity of long-term memory

  75% recall of critical details after 1 year, 45% after 5 years (Wagner's diary study)
• Duration of long-term memory

  90% recall of school friends' names after 15 years, 80% after 48 years (Bahrick)
• Cognitive tests of memory like the multistore model are often highly artificial, have low mundane realism, and are conducted in lab environments, so findings may not generalize to real-world memory use
• Types of long-term memoryDeclarative (explicit, conscious)

  • Episodic (experiences and events)
  • Semantic (facts and knowledge)
  • Procedural (skills and habits)
• Children with hippocampal damage had episodic amnesia but intact semantic memory, suggesting they use different brain regions (Vargha-Khadem)
• Clive Wearing had retrograde amnesia for episodic and semantic memories, but could gain new procedural memories through repetition, suggesting the types of long-term memory use different brain areas
• Generalizing findings from idiographic case studies to explain memory in the wider population is problematic, as other unknown issues unique to the individual could explain the behaviour
• Working memory model


  An active processor made of multiple stores, replacing the short-term memory store in the multistore model
• Central executive


  Receives sense information, controls attention, and filters information before passing to subsystems
• Phonological loop


  Processes sound information, contains acoustic store and inner voice for subvocal repetition, capacity of 2 seconds
• Visuospatial sketchpad


  Processes visual and spatial information, contains visual cache and inner eye
• Episodic buffer


  Added in 2000 to hold and combine information from the subsystems and long-term memory
• Performing two visual tasks impaired performance more than a visual and verbal task, suggesting the subsystems are separate (Baddeley)
• Brain injury patient KF had selective impairment to verbal short-term memory but not visual functioning, suggesting the subsystems are separate processes in the brain (Shallice and Warrington)
• More prefrontal cortex activation when integrating spatial and verbal information, suggesting the episodic buffer exists in the prefrontal cortex (Prabhakaran)
• Participants could recall more monosyllabic words than polysyllabic words, suggesting the capacity of the phonological loop is limited by the time it takes to say the words (Baddeley)
• The working memory model seems more accurate than the short-term memory component of the multistore model in describing how memory is used as an active processor
• Memory tasks used in research often lack mundane realism, so findings may not generalize to real-world memory use
• The central executive concept in the working memory model needs further development, and the inclusion of the episodic buffer is part of this
• It is impossible to directly observe the processes described in memory models, so inferences and assumptions must be made that could be incorrect
• Interference theory of forgetting


  Forgetting occurs because long-term memories become confused or disrupted by other information
• Proactive interference


  Old information disrupts the recall of new information
• Retroactive interference


  New information disrupts the recall of old information
• Similarity interference


  Interference is more likely when the information is similar due to response competition
• Time sensitivity interference


  Interference is less likely when there is a large gap between learning and retrieval
• Retrieval failure due to absence of cues

  Information is in long-term memory but forgotten due to lack of appropriate prompts or cues
• Context-dependent cues


  Aspects of the external environment act as cues to memory
• State-dependent cues


  Aspects of the internal environment, such as emotions or arousal, act as cues to memory
• Retroactive interference


  New information disrupts old information
• Proactive interference


  Previously learned information disrupts the learning of new information
• Interference only explains forgetting when two sets of information are similar and one learned closer together in time
• Context dependent cues


  Aspects of our external environment that work as cues to memory, such as sight, sound, and smells