Coding, Capacity & Duration

• Sperling (1960) did research into capacity of the sensory register
• Sperling showed participants 12 letters for 50 milliseconds and then played a tone (high, medium or low pitch) which corresponded to a row of letters they had to remember
• Triesman (1964) did research into the duration of the sensory register
• Triesman played an auditory message followed by a second message which was either the same message or different. The time delay varied from less than a second to more than two seconds
• Sperling found that the sensory register is relatively large, despite having a very short duration
• Triesman found that the duration of the sensory register for auditory information is less than two seconds
• Crowder (1993) did research into the coding of the sensory register
• Crowder showed participants visual and auditory information and were asked to recall the information immediately, after a few milliseconds or after a few seconds
• Crowders research suggests that the coding for the sensory register is different for different senses and can be held for different time lengths
• visual information is encoded by iconic store
• auditory information is encoded by echoic store
• Jacobs (1890) did research into the capacity of the short term memory
• Jacobs research shows that the capacity of the stm can hold on average 7 items of information
• Miller (1956) made everday observations and noted that things come in sevens
• Miller's research suggests that the capacity of the stm is around seven items
• Miller found that people could recall five words as well as they can recall five letters which they do through 'chunking'
• chunking is grouping the material into meaningful units
• Peterson and Peterson (1959) did research into the duration of the stm
• Peterson and Peterson shows participants trigrams and were asked to recall the trigram or use the Brown-Peterson technique to prevent maintenance rehearsal
• The brown-Peterson technique involved participants counting backwards in threes from a specific number for a length of time. The longer the time maintenance rehearsal was prevented, the fewer trigrams were recalled
• Baddeley (1966) did research into the coding of the stm
• Baddeley asked participants to remember a list of words that were either acoustically similar or dissimilar
• Baddeley found that the stm encodes acoustically as participants were more able to remember acoustically dissimilar words
• Bahrick asked participants between the ages of 17 and 74 to name as many of their class mates as possible from either a name recognition test or a photo recognition test
• Bahrick's research found that participants who had left school up to 47 years ago could identify 80% of class mates using the name test and 70% using the photo test
• Bahrick's research suggests that the duration of the ltm is very long
• coding is the way in which information is translated into a form which the memory store can understand
• capacity is the amount of information which can be held in a memory store
• duration is the length of time that information can be held in a memoy store
• Baddeley asked participants to remember a list of words that were either semantically similar or dissimilar
• Baddeley found that the long term memory encodes semantically as participants were more able to remember semantically dissimilar words
• Sensory register

  • capacity: relatively large
  • duration: less than 2 seconds
  • coding: different for every sense
• Short term memory:

  capacity: 7 +/- 2 items

  duration: 18 seconds

  coding: acoustically
• Long term memory:

  capacity: unlimited

  duration: up to a lifetime

  encoding: semantically
• Evaluation of Peterson & Peterson & Baddeley experiment:

  • :( low ecological validity
  • findings cannot be generalised to real life settings
  • both studies use artificial stimuli which is unlike information we are required to remember in everyday life
  • findings therefore have limited application to real life settings
• sensory register researchers:

  • capacity- Sperling 1960
  • duration- Triesman 1964
  • encoding- Crowder 1993
• Short term memory researchers:

  • capacity- Jacobs
  • duration- Peterson & peterson
  • coding- Baddeley
• Long term memory researchers:

  duration- Bahrick 1975

  coding- baddeley 1966
• Bahricks evaluation:

  • high external validity
  • findings can be generalised to real life settings
  • real life memories were studied as required recall of classmates
  • however, confounding variables were not controlled, for example he may have picked people who regular look at their yearbook photos allowing for them to rehearse memorones
• Peterson & petersons experiment evaluation:

  • lacks internal validity
  • when the procedure doesn’t measure what it intends to measure
  • participants were asked to count backwards in 3s from 100 to prevent maintenance rehearsal
  • original information may have been lost through displacement, meaning not a valid way to measure duration of the short term memory