coding, capacity, duration studies

• Encoding


  The format that 'raw' information is converted to when storing and retrieving such 'traces'
• Types of encoding

  • Visual (as an image)
  • Acoustic (as a sound)
  • Semantic (through its meaning)
• Encoding process (according to Atkinson and Shiffrin's multi-store model of memory)

  Information from the senses must be encoded to enable transfer from the initial Sensory Register to Short Term Memory (STM), and in turn onto Long Term Memory (LTM)
• Encoding examples

  • Repeating a phone number or email address to yourself (acoustically)
  • Imagining the piece of paper you saw it written on (visually)
• Acoustic encoding

  Generally thought to be the dominant method for coding information stored in Short-Term Memory (STM)
• Semantic encoding

  • Tends to be dominant when storing and retrieving information in Long Term Memory (LTM), although it can also be represented acoustically or visually
  • Involves using current knowledge to give meaning to information
• Coding

  The format or 'type' of information which is stored in each memory store
• Coding in short-term memory

  • Acoustic
• Coding in long-term memory

  • Semantic
• Baddeley (1966) found that more mistakes are made when recalling acoustically similar words straight after learning them, whilst more mistakes are made when recalling semantically similar words 20 minutes after learning them (LTM recall)
• Capacity

  The volume of information/data which can be kept in any memory store at any one time
• Capacity of short-term memory

  • 7 +/- 2 items (Miller)
• Capacity of long-term memory

  • Unlimited
• Miller's idea that things come in groups of 7 suggests that we are predisposed to remembering this quantity and that such a 'chunking' method can help us recall information
• Jacobs demonstrated that the mean letter span was 7.3 and the mean digit span was 9.3 (i.e. the number of letters or digits we can recall after increasing intervals)
• Duration

  The amount of time that information can be stored in each memory store
• Duration of short-term memory

  • 18-30 seconds (Petersen et al, 1959)
• Duration of long-term memory

  • Unlimited (Bahrick et al, 1975, yearbook study)
• Petersen et al (1959) found that increasing retention intervals decreased the accuracy of recall of consonant syllables in 24 undergraduates, when counting down from a 3 digit number (preventing mental rehearsal)
• Bahrick et al (1975) found that photo recognition of graduating classmates of the 396 participants decreased from 90% to 70% between 15 years and 46 years of graduating
• Historical psychological research


  Lack of standardisation and appreciation of scientific methods
• Current laboratory experiment methodology produces highly reliable and valid data through controlling and so removing the effects of extraneous and confounding variables
• Jacobs' research may have been influenced by confounding variables such as a noisy room or difficult word lists, leading to unreliable results
• Bahrick et al's 1975 yearbook study

  • Use of meaningful stimuli
  • Methodology high in mundane realism
  • Methodology high in external validity
• Bahrick et al's findings have high ecological validity because they can be generalised to real-life, due to the stimuli reflecting those which we would often try to learn and recall in day to day lives: information with personal and meaningful value
• Petersen et al and Miller et al studies feature methodologies with low mundane realism, thus producing findings with low ecological validity due to use of artificial stimuli which has low personal meaning to the participants
• More recent research has suggested that Miller may have over-exaggerated the capacity of short-term memory, and that the capacity is more similar to 4 chunks as opposed to the original 5-9 limit
• Miller's outdated methodologies and lack of control over confounding variables may have contributed to this inaccurate estimate of short-term memory capacity
• Short term memory

  • Coding is mainly acoustic
  • Capacity is between 5 and 9 items on average
  • Duration is between 18 and 30 seconds
• Long term memory

  • Coding is mainly semantic (meaning)
  • Capacity is unlimited
  • Duration is unlimited