FEATURES OF MEMORY

• Capacity:

  • The amount of information that can be held in memory 
• Duration:

  • The amount of time information can be held in a memory store
• Coding:

  • The format in which information is stored in a memory store
• CAPACITY OF STM: Jacob’s Digit Span (1887)

  • Measured digit span- recall a 4 digit then 5 digit then 6 digit number or letter 
  • Mean for numbers- 9.3, Mean for letters 7.3
• Strengths of Jacob’s Digit Span:

  • Standardised procedure in a lab setting
  • Study has high level of control 
  • Allowed for replication- Bopp & Verhagen (2005)
• Weakness of Jacob’s Digit Span:

  • Lacks mundane realism
  • Low ecological validity
• Miller’s Magic Number (1956)

  • Magic Number- 7 + / - 2
  • Most adults store between 5-9 items in their short-term memory
• WEAKNESSES OF MILLER’S MAGIC NUMBER:Opposing Theory:

  • Cowan (2001) reviewed other research
  • Capacity- actually 4 (+/-1)
• Duration of STM: Peterson & Peterson (1959):

  • Each ppt given trigram (e.g. GWN) and a 3 digit number (e.g. 739)
  • Told to count back from the 3 digit number until told to stop (after 3, 6, 9, 12, 15, 18s)
  • Then they had to recall the syllable
  • Results- longer delay- less info recalled (after 3 seconds- average recall 80%, after 18 seconds average recall was 3%)
  • Rapid loss of info from memory when rehearsal is prevented- short term memory has a limited duration of 15-18 seconds
• Strengths of Peterson & Peterson’s research:

  • High reliability- Repeated many times
  • Standardised procedures in the material used (trigrams and set recall times) 
  • Took place in a lab allowing for high control / replication
• Weaknesses of Peterson & Peterson’s research:

  • 24 students- Unrepresentative sample- Low generalisability
  • Lacks mundane realism- Low ecological validity
  • Artificial stimuli- meaningless trigrams- doesn’t reflect how real life works
• Duration of LTM- Bahrick et al (1975)

  • 392 ppts aged 17-74 tested
  • Ppts memory for members of their graduating class- either with free recall / photo recognition 
  • Free recall - 60% accurate after 15 years, 30% accurate after 48 years
  • Photo recognition - 90% accurate after 15 years, 70% accurate after 48 years
• Strengths of Bahrick et al’s research

  • Material used in research (remembering names and faces of people they originally knew) have a high mundane realism
• Weaknesses of Bahrick et al’s research:

  • Lack of control over extraneous variables e.g. keeping in touch, reunion 
• Coding of short & long-term memory- Baddley 1966:

  • Ppts learned 1 of 4 word lists- recalled immediately (testing STM) and 20 mins after (testing LTM)
  • List 1: Acoustically Similar (sounded the same e.g. hat, cat, bat)
  • List 2: Acoustically Dissimilar (sounded different e.g. hat, stage, ball)
  • List 3: Semantically Similar (had the same meaning e.g. big, large)
  • List 4: Semantically dissimilar (had different meanings e.g. gate, big)
• FINDINGS- CODING OF STM / LTM:

  • List 1- Worst recalled in STM, therefore info in STM is coded according to sound (similar sounding words conflicted) 
  • List 3- Worst recalled in LTM, therefore info in LTM is coded according to meaning (info with similar meanings conflicted with each other) 
• Strengths of Baddeley’s research into duration of STM / LTM:

  • Identified clear difference in coding between STM & LTM
  • Led to development of MSM
• Weaknesses of Baddeley’s research into duration of STM / LTM:

  • Artificial stimuli used (random word lists) which are meaningless and lacks mundane realism- lists had no personal meaning to ppts