psych

• Short-term memory (STM)


  Temporarily stores information received from the SR. Active memory system, contains current information being thought about. Differs from LTM in coding; capacity; duration and how information is forgotten.
• Coding in STM


  Information from SR is encoded into STM and formatted in a way that is easily understood.
• Information in STM is coded in several ways

  Visually- by thinking of an image

  Acoustically - by repeating information presented.

  Semantically- by finding meaning in information presented.
• Coding in STM-Research


  Baddeley (1966) investigated influence of acoustic and semantic similarities in STM & LTM memory for word sequences.
• Classic research by Baddeley

  To assess whether coding in STM and LTM is mainly acoustic or semantic.
• Procedure


  75 Ppts presented with one of four word lists repeated four times.

  List A- acoustically similar words

  List B- acoustically dissimilar words

  List C- semantically similar words

  List D- semantically dissimilar words.
• Testing coding in STM


  Ppts given a list containing original words in wrong order. Tasked to rearrange words in correct order.
• Testing in coding in LTM

  Ppts given a list containing original words in wrong order, but with a 20-minute interval before recall where ppts performed another task to prevent rehearsal. Then tasked to rearrange words in correct order.
• Design


  Independent design
• DV


  The number of words recalled
• IV


  Whether lists of words are acoustic/semantic
• Method


  Laboratory study
• Conclusion of Baddeley's research

  For STM, since List A was least recalled, it seems there's acoustic confusion in STM, suggesting STM is coded on an acoustic basis.

  For LTM, since List C was least recalled, it seems there's semantic confusion in LTM, suggesting LTM is coded on a semantic basis.
• Result of Baddeley's research

  For STM, ppts given List A (acoustically similar) recalled 10% as they confused similar-sounding words. Recall for other lists between 60-80%.

  For LTM, ppts with List C (semantically similar) recalled 55% as they confused similar meaning words. Recall for other lists between 70-85%.
• Evaluations


  Showed causality and effect; lacks ecological validity but can be replicated.
• Posner & Keele (1967) visual coded study results


  Showed visual coding in STM, in which 'A' followed by 'A' was faster assessed than an 'A' followed by small letter 'a' showing differences in visual coding.
• Capacity of STM


  STM has a limited capacity- research indicates that between five to nine items can be held, but can be increased by Chunking (grouping information into larger units). Miller's (1956) study in which five to nine chunks could be held at any one time.
• Capacity of STM- Research


  Jacobs (1887) tested STM capacity with serial digit span method-ppts presented with increasingly long lists of numbers or letters to recall in order of presentation.
• Jacob's (1887) research- Results

  1- When ppts fail on 50% of items-judged as having reached their capacity.

  2- Found that capacity for numbers was nine items; for letters was seven items- showing limited capacity of STM.
• Other factors that influence STM capacity

  Age and practice, though STM limitations could be due to processing limitations associated with attention.
• Duration of STM


  Amount of time information remains within STM without being lost is a maximum of 30 seconds. Can be extended by rehearsal and if done long enough transfers into LTM.
• Duration of STM- Research

  Peterson & Peterson (1959) read trigrams and then counted abckwards in threes from large three-digit number (to prevent repetition of words) for varying periods.
• Peterson & Peterson (1959)- Results

  Found that 90% of trigrams recalled correctly after three seconds, only 10% after 18 seconds. Suggesting STM duration to be between 20-30 seconds.
• Evaluations of Peterson & Peterson (1959) study

  1. Results maybe flawed as different trigrams were used in each trial causing possible interference between items, decreasing recall.

  2. No ecological validity as recalling trigrams has little relevance to everyday life.
• definition of coding , duration + capacity ?

  coding - the way different memory systems store info

  duration - how long info can be stored for

  capacity - how much info can be stored in memory
• what is the coding / capacity / duration of sensory register ?

  coding - iconic/echoic (raw unprocessed info)

  duration - very limited

  capacity - unlimited
• what is the coding / capacity / duration of STM ?

  coding - acoustically(Baddeley 1966)duration - 30s(Peterson + Peterson , 1959)capacity - 7+/-2(Miller)
• what is the coding / capacity / duration of LTM ?

  coding - semantically(Baddeley, 1966)capacity - unlimitedduration - unlimited/lifetime(Bahrick et al ,1975)
• Baddeley (1966a, 1966b)


  group 1 (acoustically similar) can,cab,cat

  group 2 (acoustically dissimilar) pit,toe,cow

  group 3 (semantically similar) great,large,big

  group 4 (semantically dissimilar) good,huge,hat

  
  

  findings -

  More mistakes, are made when recalling acoustically similar words straight after hearing them (stm) whilst more mistakes are made when recalling semantically similar words, 20 minutes after learning them (ltm recall)
• Miller (1956) Capacity of STM


  - STM capacity increased by chunking (=grouping digits/letters into chunks)

  - immediate memory span determined by no. chunks (7+-2) of info we can hold rather than individual digits/letters (JACOB)
• Peterson and Peterson (1959) duration of STM


  - 24 grad students (participated in 8 trials)- given 3 letter trigram for each test (YCG)+ 3 digit no. they had to remember- asked to recall consonant syllable after a retention interval (3 , 6 , 9 , 12 , 15 or 18s)- during retention interval participant had to count back from 3 digit no. given (preventing rehearsal)

  findings- increasing retention intervals decreased accuracy of recalling consonant syllables- on average participants were correct :90% correct after 3s20% correct after 9s2% correct after 18s
• Bahrick et al (1975) Duration of LTM


  tested 400 people on memory of classmates (17-74yrs)- recall tested in free recall (list names they remembered) or photo recognition ( shown 50 photos from yearbook)

  findings15 yrs after graduation = 90% acc. (photo recognition)48 yrs after graduation = 70% acc. (photo recognition)15 yrs after graduating = 60% acc. (free recall)48yrs after graduating = 30% acc. (free recall)
• (AO3) lacking validity :Jacob's study was conducted in 1887, a very long time ago. Early research in psychology often lacked adequate control. For example, some participants may have been distracted while they were being tested so they didn't perform as well as they might. This would mean that the results might not be valid because there were confounding variables that were not controlled.

  
  

  limitation - not only does Jacob study lack temporal validity but there's likely many possible cofounding variables that researchers failed to control , reducing external validity
• (AO3) lacking validity - counter point

  However the result of Jacobs study have been confirmed in later research

  
  

  strength - this increases reliability of Jacobs research.
• (AO3) high external validity :

  Bahrick's study used real-life meaningful memories. When studies of LTM have been conducted with meaningless picture to be remember, recall rates were lower (Shepard, 1967).

  
  

  strength - using meaningful stimuli increases external validity of such research
• (AO3) high external validity - counter argument


  The downside of such real-life research is that confounding variables are not controlled, such as the fact that Bahrick's participants may have looked at their yearbook photos throughout the years thus rehearsing memories over the years.

  
  

  limitation - cofounding variables reduce internal validity of research
• (AO3) artificial stimuli :

  Baddeley used artificial stimuli rather than meaningful material. The word lists had no personal meaning to participants. This means we should be cautious about generalising findings to different kinds of memory tasks. For example, when processing more meaningful information, people may use semantic coding even for STM tasks.

  
  

  limitation - findings from Baddeley's study has limited real world application . Findings lack mundane realism
• How many pp's Baddeley's study

  75
• How many minutes classed asLTM on Baddely's

  20
• Baddeley's results


  10% STM AS, 55% LTM SS