Coding, Capacity and Duration of Memory

• Coding


  The format in which information is stored in the various memory stores.
• Baddeley research on coding

  - Gave different lists of words to 4 groups of participants (acoustically/semantically similar or dissimilar)

  - Found that when told to recall immediately, they did worse on acoustically similar words and when recalled 20 minutes after, they did worse of semantically similar words.
• Short-term memory (STM)


  A limited-capacity store that can maintain unrehearsed information for about 20 to 30 seconds.
• Acoustically


  Refers to sounds or the sense of hearing
• Long-term memory (LTM)


  The system of memory into which all the information is placed to be kept more or less permanently.
• Semantically


  With regard to meaning.
• Strength of research on coding

  Separate memory stores

  - Led to the multi-store model.
• Limitation of research on coding

  Artificial stimuli

  - Word lists had no personal meaning to participants.

  - Therefore has limited application.
• Digit Span


  - The number of digits a person can remember.

  - Digit span is used as a measure of the capacity of short-term memory.
• Capacity


  - How much information can be stored within memory.

  - The amount of data that can be held varies between the different levels of memory.
• Jacobs (1887) Capacity of STM

  - Study on STM capacity.

  - Participants saw increasingly long lists of numbers or letters and had to recall them in the right order.

  - Two-syllable letters or numbers were left out.

  - Capacity for numbers was 9, and for letters it was 7.

  - Concluded that STM capacity had a longer digit span for numbers than letters.
• Miller (1956) Capacity of STM


  - STM capacity increased by chunking.

  - Immediate memory span determined by number of chunks (7+-2) of info we can hold rather than individual digits/letters.
• Chunking


  Combining small pieces of information into larger clusters or chunks that are more easily held in short-term memory.
• Strength of research on capacity

  A valid study

  - Jacob's study has been replicated and similar results have been found.
• Limitation of research on capacity

  Not so many chunks

  - Cowan reviewed other research and concluded that the capacity of STM is only about 4 chunks.
• Duration of memory


  - How long information can be stored within memory.

  - The amount of time that data can be held varies between the different levels of memory.
• Peterson and Peterson (1959) Duration of STM

  - Subjects asked to remember 3-consonant groups.

  - Prevented subjects from rehearsing by counting backward by threes (known as a rehearsal-prevention task).

  - After 3 seconds, subjects recalled letters only half the time.

  - After 12 seconds, subjects recalled letters about 13% of the time.

  - After 18 seconds, memory for letters almost completely gone.

  - Without active processing (like rehearsal), short-term memories die quickly.
• Consonant Syllable


  Three letter chunks with no vowels also called a trigram.
• Bahrick et al (1975) Duration of LTM


  - This study asked participants to recall students from their high school by name or by face.

  - It found that autobiographical memory is reliable, but recognition is more reliable than free recall of names or faces.

  
• Limitation of research on duration

  Meaningless stimuli in STM study

  - Lacks external validity.
• Strength of research on duration

  High external validity

  - Bahrick's study used meaningful stimuli.