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. To use the information it must be passed back to short-term memory
• 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 for critical details after 1 year, 45% after 5 years (Wagner)
• Duration of long-term memory

  90% recall of school friends' names from photographs after 15 years, 80% after 48 years (Bahrick)
• Cognitive tests of memory like the MSM are often highly artificial, low in mundane realism, and conducted in lab environments, so findings may not generalize to day-to-day 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)
• Children with hippocampal damage had episodic amnesia but intact semantic memory, suggesting semantic and episodic memory use different brain regions
• Clive Wearing had retrograde amnesia for episodic memories but intact semantic and procedural memories
• Generalizing findings from idiographic clinical case studies to explain memory in the wider population is problematic, as other unknown issues could be unique to that individual
• Working memory model

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

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


  Processes sound information, contains acoustic store and subvocal rehearsal process, capacity of 2 seconds
• Visuospatial sketchpad

  Processes visual and spatial information, contains visual cache and inner scribe
• 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
• Brain injury patient KF had selective impairment to verbal short-term memory but not visual functioning, suggesting the subsystems are separate processes
• 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)
• Memory tasks used in studies often lack mundane realism, so findings may not generalize to everyday memory use
• The central executive concept needs further development, and the inclusion of the episodic buffer is part of this
• It's 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

  • Proactive interference (old information disrupts new)
  • Retroactive interference (new information disrupts old)
  • Similarity interference (more likely with similar information)
  • Time sensitivity interference (less likely with longer gaps)
• Retrieval failure due to absence of cues

  • Encoding specificity principle (context-dependent cues)
  • State-dependent cues (internal environment)
• Retroactive interference

  New information disrupts old information
• Proactive interference

  New information being stored interferes with the recall of old information
• Similarity interference

  More likely to occur when the two pieces of information are similar due to response competition
• Time sensitivity interference

  Less likely to occur when there's a large gap between learning and retrieval
• Retrieval failure due to the absence of cues

  Information is in long-term memory but forgetting happens due to the absence of appropriate cues
• Context dependent cues

  Aspects of our external environment work as cues to memory
• State dependent cues

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

  Providing cues that relate to the organization or category of memories
• Age recall

  The most effective cues have fewer things associated with them
• The lack of organization cues inhibits memory