Coding, capacity and duration

• Coding

  The process of converting information between different forms (memory stores) 
• Research on coding:

  Alan Baddeley gave lists of words to 4 groups to remember. Group 1&2- acoustically similar and dissimilar words. Group 3&4- semantically similar and dissimilar words. Participants were then shown the words and asked to recall them in order. Recalling from short term memory (by doing immediately) they did worse with acoustically similar words. Recalling from long term memory (by doing 20 mins after) they did worse with semantically similar words.  
• Research on coding: Findings and strengths and weakenesses

  Alan Baddely (1966) found that: information is coded acoustically in STM and semantically in LTM.  

  + Clear difference between two memory stores (Multi store memory) - Artificial stimuli word lists had no meaning to participants so cannot apply to everyday life (low external validity)
• Capacity

  The amount of information that can be held in a memory store  
• Research on capacity

  Joseph Jacobs Digit span (1887). Researcher reads 4 digit if the participant gets right they move onto 5 digits etc. 

  Findings: mean span for digits was 9.3. Mean span for letters was 7.3. 

  + has been replicated 
• Research on capacity

  Span of memory and chunking- George Miller (1956). Noted everything came in 7s. Miller thought that the capacity of STM is 7±2. We do this by chunking- grouping sets of digits or letters into chunks  

  -May have overestimated STM capacity. Nelson Cowan (2001) only 4±1 chunks 
• Duration

  Length of time information can be held in memory 
• Research on Duration

  STM- Peterson&Peterson (1959). Tested 24 students in eight trials each. On each trial the student was given a consonant syllable (YCG) to remember. Student was also given 3 digit number to count backwards from to stop mental rehearsal.  On each trial, they were told to stop after 3, 6, 9, 12, 15 or 18 seconds. After 3 seconds, average recall was about 80%, after 18 seconds it was 3%.  

  Findings: STM duration is 18 seconds

  -Artificial stimuli (lacked meaning to pps) so lacks external validity 
• Research on Duration

  LTM- Henry Bahrick et al (1975)- 392 American participants aged between 17 and 74 recalled high school yearbooks. 1) Photo recognition test 2) Free recall where participants recalled names. Within 15 years of graduating 90% accurate, After 48 years 70% in photo recognition. Free recall- 60% in 15 years, 30% in 48 years.  

  Findings: LTM lasts up to a lifetime  

  + High external validity as researchers investigated meaningful memories