coding capacity and duration

• what is memory 


  ability to take info, store it and then recall it at a later time
• memory is broken into three stages: encoding, storage and retrieval
• semantic - meaning

  acoustic- sound
• coding is how the information is processed to get into the store
• capacity is how much info the store can hold
• duration is how long info can be stored for
• we encode info into the sensory register from the five senses
• we encode info into STM acoustically
• we encode info to LTM semantically
• research done on coding in STM


  • Baddeley (1966) gave participants 6 letter sequences to remember
  • when recall was immediate the letters that didnt sound the same were remembered best
  • shows STM uses acoustic coding as similar SOUND letters were hard to different
• research done on coding in LTM 


  • Baddeley gave participants a list of semantically similar words or disimilar
  • waited 20 mins before recall
  • recall was best for disimlar
  • LTM uses semantic as words were muddled due to similar meaning
• strength of researxh into coding 


  • well controlled
  • all participants received exactly th same instructions and procedure
  • easy to replicate to test on reliability
  • important features of science which makes it scientific
• weakness of research into coding

  • ecological validity: includew random words
  • stimuli faced with on a daily basis may be coded in diff ways
  • findings don’t apply to wider contexts
• research done on capacity of STM


  • miller (1956) concluded capacity of STM is 5-9 items
  • meaning we can hold that amount of items before they are forgotten
• research on chunking

  • miller suggested can improve STM through chunking
  • grouping info to make it meaningful
• research about digit span 


  • miller research supported by jacob’s (1887)
  • serial digit span technique used where ppts were given one letter or number to recall. if gotten right on recall they were five two and so on until a mistake
  • 9.3 digits remembered
  • 7.3 letters remembered
  • supports idea STM holds only 5-9 items
• strengths of research into capacity of STM 


  • high degree of control
  • reliable
• weaknesses on reseatch into capacity of STM 


  • low temporal validity
  • low ecological validity
• a trigram is a random 3 letter sequence
• duration of the sensory register:

  • iconic store: 0.5 seconds
  • echoic store: 4.2 seconds
• duration of the STM:

  • peterson and peterson (1969)
  • participants given trigrams to recall after eithr 3,6,9,12,15 or 18 seconds
  • 3 sec- 80% recall
  • 6sec- 50% recall
  • 18sec- less than 10%
  • duration of STM not much longer than 18 seconds
• evaluation of research into duration of STM: 


  • high control
  • reliable
  • low ecological validity
• research into duration of LTM: 


  • Bahrick et al (1975)
  • investigated memory of schl friends
  • 392 US ex high school students given 4 tests -free recall of names, photo recognition, name recognitio, name and photo matching
  • recognition easier than recall, test 3 showed accuracy
  • 90% accuracy in face recognition after 15 yrs
• evaluation of research into duration of LTM 


  • lack ecological validity
  • can’t generalise data
  • poor control
• factors affecting duration of STM


  • rehearsal: involves going over info in some way, 2 main types: maintenance rehearsal- repeating info, elaborative rehearsal- making info meaningful
  • knowing you have to recall: if you don’t realise you will be tested duration tends to be shorter
• factors affecting duration of LTM


  • type of material: Conway et al (1991) found that some areas of a psych course were better remembered over time due to learning of skills
  • depth of learning: duration is longer for info you learn well to begin with