Types of Memory

Types of Memory

1. Most psychologists agree that there are 3 types of memory

   • Sensory Register: Temporary store with limited capacity and duration; constantly receiving info from senses, unless we pay attention to it info disappears through spontaneous decay. coding depends on the sense info came from
     • Sperling (1960) -Method: lab experiment with 2 conditions; participants had 50 miliseconds to recall either whole grid (3 lines of 4 letters) or just one row. Results: whole grid = 4/5 letters, one row = 3 letters. Conclusion: didn't know which row was going to be selected, showed they held whole grid in sensory register but it had faded by the time they recalled 3 letters
       • Lab experiment - good control of variables. Reliable
       • artificial setting means low ecological validity, might not be realistic test of sensory register
       • Independent groups design, no order effects
       • No Control over individual differences (independent groups design)
   • Short Term memory: limited capacity and duration - coding is acoustic (sound)
     • Peterson and Peterson (1959) - Method: participants were given a trigram (3 random letters e.g. CVM) and asked to recall after 3,6,9,12,15,18 seconds and told to count backwards from a given number to stop them repeating the trigram in their heads. Results: after 3 seconds 80% recalled, after 18 seconds only 10% recalled. Conclusion: when rehearsal is prevented little can stay in STM longer than 18 seconds
       • Lab experiment - Good control of Variables. Reliable
       • Artificial so low ecological validity, not realistic
       • only one type of stimulus used, could be different for variety of stimuli
       • repeated measures design - each participant did each condition, led to order effects which cause confusion or could be proactive interference
   • Long Term Memory: unlimited capacity and is permanent, coding is semantic.
     • Episodic Memory: stores info about events and places, emotions you may have felt whilst there - memories are declarative (can be consciously recalled)
     • Semantic Memory: facts and knowledge, e.g. capital cities
     • Procedural Memory: "muscle memory" like how to ride a bike. non-declarative
     • Bahrick et al (1975) - Method: 392 people either asked to recall names of ex-class mates (free-recall test), given photo and asked to recall names (photo-recognition test), or asked to match name to photo (Name-Recognition test). Results: 15 years after leaving school - 90% names and faces and 60% free recall, 30 years - free recall is 30%, 48 years - name recognition is 80% and photo recognition is 40%. Conclusion: Study is evidence of "very long term memories"; recognition is easier than recall, suggests memory store is there but is harder to access without cues
       • Naturalistic Experiment - High ecological validity
       • Variables not controlled, Unreliable
       • showed better recall on LTM than other studies, may be due to being naturalistic and using meaningful information
       • This type of info probably has a high rehearsal rate compared to other memories so can't be generalised to other types of memories that are unimportant

2. Each of the types of memory have different capacities

   • Jacobs (1887) - Method: participants presented with string of digits or letters and asked to recall in correct order. sequence increased in size until participant failed. Results: average was 9 digits or 7 letters, increased with age through childhood. Conclusion: based on results jacobs concluded STM has a capacity of 5-9 items, STM capacity increases with age, probably due to memory techniques e.g. chunking
     • Artificial experiment, Low ecological Validity
     • Good control of Variables. Reliable
     • Meaningful information may have a greater capacity
     • Repeated measures design, order effects may have caused confusion, Proactive interference may have hindered recall
   • Miller (1956) - meta-analysis or STM capacity research, found people can remember 7 +/-2. however chunking can be utilised to increase this capacity

3. Coding: In STM memories are kept active through repetition (acoustic coding), in LTM info is coded semantically (more useful to know meaning) although LTM can be coded visually or acoustically

   • Baddeley (1966) - Method: indépendant groups design, given 4 words that were either: acoustically similar (cat, bat), acoustically disimilar (pit, cow), semantically similar (big, large) or semantically disimilar (good, hot) and asked to recall either immediately or after a 20 minute task. Results: if recalling instantly (STM) there was a problem with acoustically similar words, if recalling after a task (LTM) they had problems with semantically similar words. Conclusion: confusion of similar words suggests that STM relies on acoustic coding and LTM on Semantic.
     • Artificial so low ecological validity.
     • didn't consider the other types of LTM (episodic or procedural, determinist by assuming this is how LTM codes when no effort has been made to investigate other types
     • Didn't consider other methods of coding (visually)
     • Independent groups design - no order effects
     • Independent groups design, no control over individual differences.
     • good control of all variables except individual differences