Memory

• Coding


  The way information is represented in memory
• Baddeley (1966) study


  • Gave different types of words to groups
  • Asked to recall in correct order
  • Immediate recall from short-term memory
  • Recall after 20 minutes from long-term memory
• Word groups


  • Acoustically similar (cat, cab, can)
  • Acoustically dissimilar (pit, few, cow)
  • Semantically similar (large, big, huge)
  • Semantically dissimilar (hot, grass, good)
• Findings suggest information is coded acoustically for short-term memory and semantically for long-term memory
• Short-term memory vs long-term memory


  Clear difference identified
• Artificial stimuli used instead of meaningful material, so results have limited application
• Capacity


  The amount of information that can be held in memory
• Jacobs (1887) digit span study


  • Reader reads out digits, participant recalls aloud in order
  • Mean digit span 9.3 items, letter span 7.3
• Miller (1956) magic number


  Short-term memory capacity is 7 +/- 2
• People can recall 5 digits as well as 5 words via chunking
• Replication of digit span study

  Ensures results are correct, due to possible confounding variables like participant distraction
• Cowan (2001) concluded short-term memory capacity is 4 +/- 1, overestimating capacity
• Duration


  The length of time information can be retained in memory
• Peterson and Peterson (1959) study


  • Gave 3 digit and letter sequences
  • Participants counted backwards to stop rehearsal
  • Recall tested at 3, 6, 9, 12, 18 second intervals
  • 80% recall after 3 seconds, 3% after 18 seconds
• Peterson and Peterson's findings suggest short-term memory can last for 18 seconds, longer with rehearsal
• Bahrick et al (1975) study


  • Used school yearbook photos and free recall of graduation class names
  • 90% photo recognition accuracy within 15 years, 70% after 48 years
  • 60% free recall after 15 years, 30% after 48 years
• Long-term memory can last a lifetime
• Bahrick study


  High external validity due to meaningful stimulus, lower with meaningless stimulus
• Peterson and Peterson study

  Low external validity due to artificial stimulus, but some validity for remembering sequences like passwords
• Multi-store model of memory

  Separates memory into sensory register, short-term memory, and long-term memory
• Sensory register


  • Takes input from each sense, modality-specific, high capacity, 0.5 second duration
• Short-term memory


  • Acoustically coded, capacity 7 +/- 2, duration 18-30 seconds
• Long-term memory


  • Semantically coded, potentially unlimited capacity, potentially lifetime duration
• Multi-store model


  Shows separation between short and long-term memory, like mix-up of similar sounding words vs similar meaning words
• Multi-store model lacks mundane realism, is too simplistic, and may not be valid due to using digits/words with no meaning
• Prolonged rehearsal not needed to transfer to long-term memory, type of rehearsal more important
• Types of long-term memory

  Episodic, semantic, procedural
• Episodic memory


  • Mental diary of everyday lives and activities, 'time-stamped', conscious effort to recall
• Semantic memory


  • Shared knowledge of the world, generic facts not personal
• Procedural memory


  • Memory for actions/skills, recalled automatically without effort
• Case study of Molaison and Wearing

  Episodic memory impaired, semantic memory untouched, shows different types of long-term memory
• Brain injury studies lack control variables, difficult to determine pre-injury memory
• Conflicting research on location of different long-term memory types
• Working memory model


  Baddeley and Hitch 1974, includes central executive, phonological loop, visuo-spatial sketchpad, episodic buffer
• Central executive


  • Supervisor that monitors and allocates attention, doesn't hold data
• Phonological loop


  • Stores and rehearses auditory information, capacity 2 seconds of words
• Visuo-spatial sketchpad


  • Stores visual and spatial information, capacity 3-4 items
• Episodic buffer


  • Temporary store for visual, spatial and verbal information, capacity 4 chunks, links to long-term memory
• Shallice and Warrington (1970) study

  KF's brain injury impaired auditory short-term memory but not visual, supporting the model
• Dual task performance


  Decline when performing two tasks of the same type, supporting separation of subsystems