Memory

Memory

1. Duration: How long the memory lasts before it is no longer accessible

   • STM: Peterson and Peterson (1959). 24 university students were tested on recall, using “nonsense trigrams”. The experimenter would read out the trigram, e.g. AJP, followed by a random 3 digit number, e.g. 392, the participant would start counting back from the number in threes until told to stop. Then they would be asked to recall the trigram. Each participant were given two practise trials, followed by eight “real” trials. On each trial the retention interval differed: 3, 6, 9, 12, 15, 18 seconds. Peterson and Peterson found that participants remembered the trigram around 90% of the time when the retention interval was 3 seconds. However, when the retention interval was 18 seconds participants could recall the trigram only 2% of the time. The duration of our STM is less than 20 seconds.
   • LTM: Shepard(1967) Participants shown 612 pictures, one at a time. An hour later they were shown some pictures again, mixed in with some they hadn't seen. They could remember the pictures almost perfectly. 4 months later they could remember 50% of the pictures.
   • LTM: Bahrick et al(1975) Showed people of various ages pictures from their highschool yearbook and asked them to name the person. 70% accurate, even after 48 years

2. Multi Store Model (Atkinson and Shriffin, 1968)

   • Stimuli
     • Sensory Store: recieves info constantly, can only be held for 1/2 a second.
       • Attention
         • STM: Info will disappear quickly if not rehearsed (Maintenance
           • Elaborative Rehearsal
             • LTM: Info passed through elaborative rehearsal. Info can be transferred back to STM through retrieval.
   • Sperling (1960): Duration of sensory store, participants saw a grid of letters for 50 milliseconds. In 1st stage, participants asked to recall whole grid, 45% remembered 5 or more items. 2nd stage, participants only asked to recall only one row of the grid, 75% could remember 3 or more from the correct row.
   • Case studies: HM and Clive Wearing

3. Working Memory Model

   • Central Executive
     • Phonological Loop
       • Holds about 2 seconds of information. Word length effect. harder to remember long words .
     • Episodic Buffer
       • LTM
       • Better at recalling sentences that single words
     • Visuo-Spatial Sketchpad
     • Dual Task Technique. Completing 2 tasks at once that use the same component causes difficulty

4. Encoding: The way that information is changed so that it can be stored in memory.

   • Baddeley(1966) conducted an experiment in which participants were presented with four lists of words, one at a time. They were asked to recall the words in order immediately after and 20 seconds later. He found that participants had trouble remembering acoustically similar words immediately but not after 20 minutes. Participants had no trouble remembering semantically similar immediately after but not 20 minutes later

5. Capacity: The amount of information that can be stored at once

   • STM: Jacobs (1887) used the “digit span” technique to assess the capacity of the STM. He found that the average span of digits that people could recall was 9.3, whereas, the average span of letters was 7.3. Miller (1956) reviewed psychological research and concluded that the capacity of the STM is between 5-9 pieces of information, he referred to this as the magic number 7 (+ or – 2). You can improve the STM by using “chunking”. The capacity of the STM is limited.
   • LTM has a potentially unlimited capacity.