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 but varies per store)
• Short-term memory


  1. Receives info from the 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 seven plus or minus 2 items
• Long-term memory


  1. Very long duration, permanent memory storage

  2. Theoretically unlimited capacity

  3. Forgotten information appears to just be inaccessible

  4. Coded semantically in the form of meaning

  5. Must be passed back to short-term memory to use the information
• Words at the start and end of word lists were more easily recalled (Primacy and recency effect)
• Recall of a random row of a 12x12 grid flashed for 1/120th of a second was 75%, suggesting all the rows were stored in sensory register but forgotten too quickly
• 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, low in mundane realism, and conducted in lab environments, so findings may not generalize to real-world memory use
• Types of long-term memory

  • Declarative (explicit, conscious)
  • Non-declarative (implicit, unconscious)
  • Episodic (experiences and events)
  • Semantic (facts and knowledge)
  • Procedural (skills and habits)
• Declarative memory


  • Can be accessed consciously and expressed in words
  • Episodic is autobiographical, influenced by emotion, associated with hippocampus and prefrontal cortex
  • Semantic is not timestamped, lasts longer than episodic, associated with frontal cortex
• Non-declarative memory


  • Not consciously recalled, difficult to explain in words
  • Procedural is unconscious memories of skills, associated with motor cortex and cerebellum
• Case studies of individuals with brain damage suggest semantic and episodic memory use different brain regions
• Clive Wearing has retrograde amnesia for episodic memories but can still remember semantic facts and procedural skills
• Generalizing findings from idiographic case studies to explain memory in the wider population is problematic due to potential unique issues in the individual
• Working memory model


  Baddeley and Hitch 1974, a theoretical counter model of information processing that replaced the short-term memory store in the multistore model
• Working memory model


  1. Central executive receives and controls attention, filters information

  2. Phonological loop processes sound information, contains acoustic store and inner voice

  3. Visuospatial sketchpad processes visual and spatial information, contains visual cache and inner eye

  4. Episodic buffer added in 2000 to hold and combine information from other subsystems and long-term memory
• Performing two visual tasks or a visual and verbal task simultaneously is better when they use separate processing subsystems, suggesting the phonological loop and visuospatial sketchpad are separate
• 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
• More prefrontal cortex activation when integrating spatial and verbal information, suggesting the episodic buffer exists in the prefrontal cortex
• 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 (word length effect)
• The working memory model seems more accurate than the short-term memory component of the multistore model in describing active memory processing, so psychologists now often refer to working memory instead
• Issues with external validity of memory studies due to lack of mundane realism and artificial tasks, 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 memory processes described in 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 new
  • Retroactive interference - new information disrupts old
  • More likely with similar information due to response competition
  • Less likely with longer time gaps between learning and retrieval
• Cue-dependent forgetting


  • Information is in long-term memory but forgotten due to absence of appropriate cues or prompts
  • Encoding specificity principle - context-dependent cues in the external environment act as memory prompts
  • State-dependent cues in the internal environment like emotions, drugs, arousal also act as memory prompts
• Retroactive interference


  New information disrupts old information
• Proactive interference


  Previously learned information causes confusion in the coding of later 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
• State dependent cues


  Aspects of our internal environment that work as cues to memory
• Category or organizational dependent cues


  Providing cues that relate to the organization or category of memories
• The most effective cues have fewer things associated with them, the lack of organization cues inhibits memory
• Retroactive interference


  • Adding new street names to memory makes recalling old street names harder
• Proactive interference


  • Previously learned word combinations cause confusion in the coding of later word lists
• Interference may only explain a temporary loss of information, not a permanent loss