Memory

• Multistore model of memory


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


  • Receives raw sense impressions, attention passes info to short-term memory, coding is modality specific, capacity is very large, duration very short 250 milliseconds but varies per store
• Short-term memory

  • Receives info from the sensory register by paying attention or from long-term memory by retrieval, keeps information by repeating maintenance rehearsal or passing information on to long-term memory, coding is acoustic, duration is approximately 18 seconds, capacity is seven plus or minus 2 items
• Long-term memory

  • Very long duration, permanent memory storage, theoretically unlimited capacity, forgotten information appears to just be inaccessible, coded semantically in the form of meaning
• 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
• Short-term memory capacity


  • Average 7 items for letters, 9 for numbers, can be improved by chunking
• Short-term memory duration


  • Less than 10% recall of a 3-letter trigram after 18 seconds if performing an interference task
• Long-term memory capacity


  • 75% recall for critical details after 1 year, 45% after 5 years, potentially limitless
• Long-term memory duration


  • 90% recall of school friends' names from photographs after 15 years, 80% after 48 years, potentially limitless
• Cognitive tests of memory like the MSM are often highly artificial, low mundane realism, and conducted in lab environments, so findings may not generalize to day-to-day memory use
• Declarative (explicit) long-term memory


  Memories that can be accessed consciously and expressed in words
• Non-declarative (implicit) long-term memory


  Memories that are not consciously recalled and are difficult to express in words
• Episodic long-term memory


  Memories of experiences and events, timestamped with time and place, declarative
• Semantic long-term memory


  Memories of facts, meanings, and knowledge, declarative, stronger and lasts longer than episodic
• Procedural long-term memory


  Unconscious memories of skills, often learned in childhood, non-declarative, more resistant to amnesia
• Children with damage to the hippocampus but not the parahippocampal cortex had episodic amnesia but retained semantic memory
• Clive Wearing has retrograde amnesia for episodic and semantic memories, but can gain new procedural memories
• Generalizing findings from idiographic clinical case studies to explain memory in the wider population is problematic due to unknown unique issues
• Episodic and semantic memories are both declarative, and episodic memories can become semantic over time
• Working memory model


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


  • The head of the working memory model, receives sense information, controls attention, and filters information before passing to subsystems
• Phonological loop


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


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


  Added to the working memory model in 2000 as a general store to hold and combine information from the other subsystems and long-term memory
• Performing two visual tasks impaired performance, while a visual and verbal task did not, suggesting the phonological loop and visuospatial sketchpad are separate systems
• A brain-injured patient, KF, had a selective impairment to verbal short-term memory but not visual functioning, suggesting the phonological loop and visuospatial sketchpad are separate processes in the brain
• More activation was found in the prefrontal cortex when information is integrated, and in posterior brain regions when not integrated, suggesting the episodic buffer exists and is in the prefrontal cortex
• Participants could recall more monosyllabic words than polysyllabic words, suggesting the capacity of the phonological loop is 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 how memory is used as an active processor
• Memory tasks used in studies often lack mundane realism and may not generalize to day-to-day memory use
• The central executive concept 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


  We forget because our long-term memories become confused or disrupted by other information
• Proactive interference


  Old information disrupts the recall of new information, working forward in time
• Retroactive interference


  New information disrupts the recall of old information, working backward in time
• Similarity interference


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


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

  Information is in long-term memory, but forgetting happens due to the lack of appropriate prompts or cues