2.1.1

• Sensory memory


  When information comes in from the senses it needs to be stored for a very small amount of time until the body's processing systems can decide what to do with it.

  
  

  The duration of SM is around 1/2a second, up to several seconds at the very most, the capacity is between 12 to 16 items, and encodes using all 5 modalities (senses).
• Five types of sensory memory

  -Iconic memory;

  
  

  - Echoic memory;

  
  

  - Haptic memory;

  
  

  -Olfactory memory;

  
  

  -Gustatory memory.
• Iconic memory


  It refers to the retention of information that comes from vision and light stimuli.
• Echoic memory


  It refers to the retention of information derived from a sound or auditory stimulus.
• Haptic memory


  It refers to the retention of information that comes from touch.
• Olfactory memory


  It refers to the retention of information derived from smell.
• Gustatory memory


  It refers to the retention of information derived from taste.
• Short-term memory


  Short-term memory (STM) has the ability to hold a small amount of information for a relatively short period of time. The amount (capacity) and duration of STM is greater than sensory memory but smaller than long-term memory It is seen more as a holding device before memory is forgotten/lost or moved to long-term memory.
• Capacity of STM


  Experiments conducted by Miller (1956) indicate the capacity of STM is 7 items or chunks plus or minus 2 (5-9 items).
• Experiments conducted by Miller (1956)


  Miller demonstrated this in an experiment where he asked participants to recall information, adding an extra bit as he moved on: A bit like the game ‘I went to the shops’. Starting participants with two or three words to recall, he gradually built it up until they made an error It was found that most participants struggled with between 5-9 words. This is known as‘Miller’s Magic 7’.
• Jacobs (1887) experiment


  Jacobs (1887) had completed a similar experiment using digits with 443 female students. He called this a digit span experiment, using numbers instead of words. His results were similar to Miller's, with 7.3 being the average recall. This supports Miller and suggests his study is valid.
• Short-term memory duration


  Around 18-30s
• Peterson and Peterson (1959) study


  In this study, participants were given non-sensical three-letter trigrams to learn e.g. CGR or BHT. These were presented visually to the participants, one at a time. The participants had to recall the trigram in the correct order after a delay of either 3s, 6s, 9s, 12s, 15s or 18s. During this delay, they were asked to complete a distraction task: usually counting backwards from 300 in 3s (300,297,294 etc.).

  
  

  A graph of the correctly recalled trigrams over time was plotted and was shown to be a decay curve. This demonstrates that over time the memory seems to decay. The graph was extrapolated to show that after the 30s recall in STM would be zero. Therefore, Peterson and Peterson stated that the duration of STM was 18-30s.