Memory

• Encoding refers to how we take in new information from our environment and convert it into a form that can be processed and remembered.
• The hippocampus is involved in the formation, consolidation, and retrieval of memories.
• Memory can be divided into three stages: encoding (the process by which information enters memory), storage (the ability to retain information over time), and retrieval (the act of recalling stored information).
• Coding


  Converting information from one store into another
• Baddeley 1966 study


  1. Gave different list of words to 4 groups of participants

  2. Group 1 - acoustically similar

  3. Group 2 - acoustically dissimilar

  4. Group 3 - semantically similar (similar meaning)

  5. Group 4 - semantically dissimilar

  6. Participants asked to recall words in the correct order from STM
• When recall task was done immediately after hearing the words (STM)


  They did worse recalling acoustically similar words - info coded acoustically into STM
• When asked to recall a word list after 20 mins (LTM)


  They did worse with semantically similar words with similar meaning - suggests info is coded semantically into LTM
• Artificial stimuli used in the Baddeley 1966 study
• Need to be careful with generalising findings from the Baddeley 1966 study to different kinds of memory tasks
• When processing meaningful information, people may not use semantic coding even for STM tasks, meaning the Baddeley 1966 study has limited application
• Digit span

  Tests how much info STM can hold at once (capacity)
• Jacobs 1887 study


  • Measured digit span by asking participants to recall a certain number of digits that increased consecutively by 1
  • Found the mean digit span to be 9.3 for digits and 7.3 for letters
• Jacobs 1887 study was conducted a long time ago, with lack of control of variables and potential confounding variables like distractions
• Span of memory + chunking

  • Miller 1956 identified that lots of things are in 7s in everyday practice, suggesting the span of STM is about 7 items
  • People recall info by chunking - e.g. grouping a set of digits/letters into units
• Miller may have overestimated the capacity of STM - it was identified STM to have a capacity of ~4 chunks of information
• Margaret + Peterson 1959 study


  1. Tested 24 undergraduate students in 8 trials

  2. Student was given a consonant syllable + 3 digit number

  3. Asked to count backwards from the 3 digit number until told to stop (to prevent any mental rehearsal of the consonant syllable)

  4. Told to stop after time intervals of 3-18s (retention interval)
• Findings from the Margaret + Peterson 1959 study


  STM may have a very short duration, unless repeated by verbal rehearsal
• The stimulus material in the Margaret + Peterson 1959 study was artificial; memorising consonant syllables does not reflect real life memory activities
• The Margaret + Peterson 1959 study may lack external validity, although e.g. phone numbers are memorised
• Bahrick 1975 study


  • Studied 392 participants between 17-74 from America
  • Obtained high school yearbooks and conducted recall activities
  • Within 15 years of graduation, photo recognition was ~90% accurate
  • After 48 years, photo recognition declined to ~70%
  • After 15 years, free recall was ~60% accurate
  • After 48 years, free recall declined to ~30%
• The Bahrick 1975 study has high external validity as it studied real-life meaningful memories
• When recall on meaningless pictures was observed, recall dropped lower in the Bahrick 1975 study
• Despite the natural setting, confounding variables were not controlled for in the Bahrick 1975 study - e.g. participants may have looked at their yearbook photos and rehearsed their memory over the years
• Multistore model of memory

  Memory is made of 3 stores with differing levels of processing: Sensory register, Short-Term Memory (STM), Long-Term Memory (LTM)
• Sensory register


  • Stores information from each sense, lasts briefly (duration of half a second), high capacity
  • Little info from the sensory register passes into the memory system, but if paid attention to, may pass into the STM store - attention is important
• Short-Term Memory (STM)


  • Limited capacity store, only contains a certain number of items before forgetting
  • Capacity 5-9 items, info coded acoustically lasts ~30s unless rehearsed
  • Maintenance rehearsal keeps info in STM through rehearsal
  • Eventually passes into LTM
• Long-Term Memory (LTM)


  • Permanent memory, stores info rehearsed for a prolonged period with unlimited capacity
  • Coded semantically
  • Material stored in LTM, when recalled, is transferred back into STM via retrieval
• The multistore model of memory suggests that none of our memories are recalled directly from LTM
• When using STM


  We mix up acoustically similar words/sounds
• When using LTM


  We mix up semantically similar words
• The multistore model research studies support that STM and LTM are qualitatively different - they have different levels of coding, capacity and duration
• The multistore model states that STM is unitary, but research shows this can't be true as amnesia patients show different STM deficits for verbal and non-verbal information
• The research suggests there must be one short-term store for visual information and another for auditory information
• There is evidence that LTM is not unitary, with separate stores for semantic memory and procedural memory
• The multistore model's suggestion that what matters in rehearsal is the amount you do is wrong - what is important is the rehearsal type (maintenance vs elaborative rehearsal)
• The research studies that provide support for the multistore model often use artificial materials like digits, letters, words and consonant syllables that would not always be attempted to remember in everyday situations, limiting the generalisability and external validity
• Episodic memory


  Ability to recall events/episodes in our lives, chronological in nature, memories are time stamped, associated with people, places, objects and behaviours, recalled with conscious effort
• Semantic memory


  Contains knowledge of the world/information and facts, encoding similar to an encyclopedia/dictionary, memories are not time stamped, less personal and about facts
• Procedural memory


  Memory for actions, skills and how we do things, recalled without conscious awareness/effort
• Clinical evidence from amnesia patients like Henry Molaison (HM) and Clive Wearing supports the idea that long-term memory is coded into different stores (episodic, semantic, procedural)