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 is 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 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 120th of a second was 75%, suggesting all the rows were stored in sensory register but a large capacity could not be written as items were 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, can be improved by chunking
• Duration of short-term memory

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

  75% recall for critical details after 1 year, 45% after 5 years, potentially limitless
• Duration of long-term memory

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

  • Declarative (explicit, conscious, e.g. episodic and semantic) and non-declarative (implicit, unconscious, e.g. procedural)
• Episodic memory


  Memories of experiences and events, timestamped, declarative, strength influenced by emotion, associated with hippocampus and prefrontal cortex
• Semantic memory


  Memory of facts, meanings, and knowledge, declarative, strength from processing depth, lasts longer than episodic, not timestamped, associated with frontal cortex
• Procedural memory


  Unconscious memories of skills, often learned in childhood, not declarative, more resistant to amnesia, associated with motor cortex and cerebellum
• Case studies of individuals with brain damage suggest semantic and episodic memory use different brain regions
• 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 to replace the short-term memory store in the multistore model, an active processor made of multiple stores
• Central executive


  • Head of the working memory model, receives sense information, controls attention, filters information before passing to subsystems, limited capacity of 4 items, can only deal with one strand of information at a time
• Phonological loop


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


  • Processes visual and spatial information, contains the visual cache for form and colour, and the inner scribe for 3D relationships
• Episodic buffer


  • Added to the working memory model in 2000, a general store to hold and combine information from the 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 systems
• Brain injury patient KF had selective impairment to verbal short-term memory but not visual functioning, suggesting the phonological loop and visuospatial sketchpad are separate processes in separate brain regions
• More activation in the prefrontal cortex when integrating spatial and verbal information, and in posterior regions when not integrating, 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 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 how memory is used as an active processor
• Memory tasks used in research often lack mundane realism and may not generalise to day-to-day 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 which could be incorrect
• Interference theory of forgetting

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


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


  • New information disrupts the recall of old information, works backwards 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
• Encoding specificity principle


  Context-dependent cues (aspects of the external environment) and state-dependent cues (aspects of the internal environment) act as prompts for memory retrieval
• Retroactive interference


  New information disrupts old information
• Proactive interference


  Previously learned information disrupts the learning of new information