Capacity (amount of information which may be stored) of the long-term memory is unknown. It is impossible to measure and may be limitless. The brains ability to store information is greater than the worlds most powerful computer memory.
Information is thought to be stored permanently - for your entire lifetime. It is now thought possible that some memories may be genetically inherited and therefore last longer than a lifetime.
The issue with duration in long-term memory relates to recall and forgetting.
Two types of encoding are thought to operate in LTM:
Research into semantic encoding in long term memory Baddeley (1966)
Baddeley presented participants with four lists to remember:
List 1: man map can cap
List 2: try pig hut pen
List 3: great big huge wide
List 4: run easy tug end
Participants had to recall as many words as possible immediately after presentation of lists and then try again 20 minutes later.
Baddeley found that the immediate recall was better for list 2 than for list 1 and with little difference in recall between lists 3 and 4.
List 1 contains similar sounding words and list 2 contains non similar sounding words. When participants were then asked to recall words after twenty minutes they recalled list 4 better than list 3, list 4 contains words with non similar meaning words and list 3 contains words with similar meanings.
There was little difference in recall for lists 1 and 2. This shows that the short-term memory tends to store information according to sounds rather than meaning and that the long-term memory tends to store information according to semantics (meaning) rather than simply sound.
Baddeley used a laboratory experiment and can therefore be criticised in terms of ecological validity, demand characteristics, participant variables/individual differences, experimenter bias and representativeness (Baddeley used undergraduate students as participants). Although it has good reliability.
The following table is a summary of what you have learnt about encoding, duration and capacity in the STM and LTM.
|S||Miller's||Brown & Peterson suggest 15 to 30 seconds.||Conrad suggested only acoustic process. Shulman suggested also visual and semantic processes.|
|T||7 +/- 2 Chunks|
|M||The magical number seven plus or minus two.|
|Unknown and impossible to measure. Maybe limitless.||Relatively permanent. Relates to theories of recall and forgetting.||Declarative and/or Procedural. Declarative may be Semantic and/or Episodic (Tulvig). Baddeley showed process was largely semantic.|