Memory, Capacity and Duration of memory

• Coding in memory

  STM: Acoustic

  LTM: Semantic
• Capacity - the amount of info that can be held

  STM: 7 +/- 2 items

  LTM: Unlimited
• Duration - the length of time info can be held


  STM: 18-30 seconds

  LTM: Indefinite
• Coding Research

  Baddeley researched coding into STM
• Baddeley's research into STM

  • Independent groups design. Participants were given four sets of words that were; semantically similar/semantically dissimilar, acoustically dissimilar\acoustically similar
  • Participants had problems recalling acoustically similar words when recalling the world list immediately from (STM). After an interval they had problems with semantically similar words
  • He found words were coded acoustically in STM and semantically in LTM
  • Strength - controlled lab study, establish cause and effect can be established
  • Limitations - Artificial tasks. Low ecological validity.
• Jacob's/Miller's research into Capacity

  • Jacob; Participants presented with a string of letters/digits. Had to repeat them back in the same order, increasing until the participant failed to recall the sequence correctly

  Results: participants recalled about 9 digits and 7 letters

  Miller: investigated capacity using a digit span test, "magical number 7"

  
  

  Strengths-Replicated research, valid and reliable.

  • Strict control over variables

  Limitations- artificial tasks, lacks ecological validity, hard to generalise

  • Previous digit sequences could have interfered with future ones
• Bahrick's research into duration (VLTMs)

  • 392 people asked to list names of their ex-classmates, then shown photos and asked to recall the names of the people shown.

  Results: Within 15 years of leaving school, participants could recognise about 90% of names and faces.

  Supports VLTMs in 'real-life' settings. Recognition is better than recall, so there may be a huge store of info, but it's not always easy to access all of it.

  Strength- field study. High ecological validity.

  Weakness - Cause and effect not established as there's low control over variables
• Peterson & Peterson - duration of STM

  • Participants were shown nonsense trigrams and asked to recall them after either 3,6,9,12,15 or 18 secs. During the pause, they were asked to count backwards in threes from a given number (interference task, prevents repeating letters internally)
  • Findings: After 3 seconds, participants could recall about 80% trigrams correctly. 18 seconds - only 10% recalled correctly

  When rehearsal is prevented, very little stays in the STM for longer than 18 seconds