Memory Lesson 1 - STM + LTM

Memory Lesson 1 - STM + LTM

1. Short-term memory

   • Memory for immediate events
   • Short duration
   • Measured in seconds and minutes rather than hours and days
   • Information will be forgotten if not rehearsed
   • Capacity of 4 chunks of information + / - 3
   • Information tends to be coded acoustically and referred to often as working memory

2. Long-term memory

   • Memory for events have happened in the past
   • Lasts from 2 minutes to 100 years
   • Has unlimited capacity and duration
   • Tends to be coded semantically

3. Capacity of Short-term memory

   • Joseph Jacobs (1887)
     • One of the earliest studies carried out to access STM capacity
     • Found easier to recall digits rather than letters
       • Due to fact that there are 26 letters and only 9 digits
   • George Miller (1956)
     • Book: The Magic Number 7 - Plus or Minus 2
     • Recall of dots flashed on the screen and stated people remember up to 7 (more or less)
       • True with letters, musical notes or words
     • Led to idea of 'chunking'
       • Recall more
   • May be more limited Cowin (2001) - lower end more likely correct 4 chunks of information retained
   • Size of chunks matters (Simon 1974)
   • Individual differences (eg, age)
     • Increased brain capacity, new learnt techniques

4. Duration

   • Peterson and Peterson (1959)
     • Test how long we can hold information
     • 8 trials
     • Intervals 3, 6, 9, 12, 15 and 18 seconds
     • Intervals counting backwards from a 3 digit number
     • Results: 3 seconds - 90% correct, 9 seconds - 20% correct, 18 seconds - 2% correct
       • Evaluation: STM has very short capacity if verbal rehearsal is prevented
       • Photo recognition
         • 15 years later 90% accurate, 48 years later 70% accurate
       • Free recall of classmates
         • 15 years 60% accurate, 48 years 30% accurate
   • Evaluation: Reitman (1974) used auditory tones rather than speech, recall was improved supporting idea of displacement rather than decay of memory

5. Coding (Baddeley 1966)

   • To store memories they need to be written/kept somehow
   • Acoustic - sounds
   • Visual - imagines
   • Semantic - meaning
   • Acoustically similar but semantically different
     • Eg, cat, cab, can, cad
   • Acoustically different but semantically similar
     • Eg, great, large, big, huge
   • Results: Difficulties remembering words acoustically similar in STM but not LTM
     • Semantically similar words were muddled in LTM but were easier to remember in the STM
     • LTM is encoded semantically
     • STM is encoded acoustically
   • Wickens et al (1976) - evidence of STM using semantic code
   • LTM may not be exclusively semantic coding
     • Frost (1972) - long term recall related to visual as well as semantic categories
     • Nelson and Rothbart (1972) found evidence of acoustic coding in LTM
       • Therefore STM and LTM can vary according to circumstance not just acoustic or semantic

6. CAPACITY: Measure of how much can be held in memory. It is represented in terms of bits of information such as number of digits

7. CODING: Way that information is changed so that it can be stored in memory. Information enters the brain via the senses. It is then stored in various forms, such as visual codes (pictures) acoustic codes (sounds) or semantic codes ( the meaning of the experience)

8. DURATION: A measure of how long a memory lasts before it is no longer available.

9. LONG-TERM MEMORY: Your memory for events that have happened in the past. This lasts anywhere from 2 minutes to 100 years. LTM has potentially unlimited duration and capacity and tends to be coded semantically.

10. SHORT-TERM MEMORY: Your memory for immediate events. STMs are measured in seconds and minutes rather that hours and days. They disappear unless they are rehearsed. STM also has a limited capacity of about 4 items or chunks and tends to be coded acoustically. This type of memory is sometimes referred to as working memory.