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  • Forgetting
    • Trace Decay
      • Info that enters STM leaves a trace in the brain due to the excitation of nerve cells
        • Neural activity dies down gradually unless material is rehearsed
      • Engram that will be formed is delicate and liable to disruption because it is an active trace
        • Hebb argued this happens whilst learning takes place
        • With learning, it grows stronger until a permenant engram is formed
      • Some researchers argue that if knowledge and skill are not used and not practiced then engram will decay
      • Hebb argues that it only applies to STM
        • when we rehearse material the corresponding neural activity causes a structural change in the brain
      • Solso also concluded that there is no evidence that the major cause of forgetting in LTM is neurological decay
      • Evaluation
        • It is difficult to test - participants are tested at different time periods
          • Could be rehearsing thus strengthening the trace
          • if rehearsal is prevented then forgetting could be due to interference from task rather than decay of memory trace
        • Waugh and Norman who set out to support trace decay concluded that interference is the most likely cause of forgetting in STM
        • Trace decay theory has a difficulty dealing with situations where items which cannot be remembered at one time can spontaneously be remembered at another time without additional presentation of items
          • If the trace has decayed it should never be available
        • The experiment of Peterson and Peterson is used as evidence for the role of decay in STM
          • Findings show that after 18 seconds the trace has almost completely decayed when rehearsal is prevented
    • Displacement Theory
      • Explains forgetting from STM in terms of a limited capacity of this store
      • There is a limited number of 'slots' in STM
        • When the system is full the oldest material is 'pushed out' or displaced by incoming information
      • Waugh and Norman - serial probe task - support displacement theory for forgetting
        • later digits displaced earlier ones
      • Evaluation
        • seems to give an adequate account of forgetting from STM when applied to the MSM of memory
        • Empirical evidence EG: Murdock - primacy/recency experimental findings - support theory
        • More recent models of memory - EG: Working memory model have indicated that STM is much more complex than the unitary, limited capacity short-term store 1st proposed by Atkinson and Sheriffin's MSM of memory
    • Interference Theory
      • What occurs before, during and after learning
      • At beginning of storage process, interference can prevent new info from passing STM to LTM.
        • In LTM, as the store of info grows, there will be increasing interference between competing memories
      • Two types of interference:
        • Proactive
          • where earlier learning interferes with what you are trying to learn at present
            • EG: You have learnt Spanish and now you struggle learning French
        • Retroactive
          • where more recent learning interferes with the recall of earlier material
            • EG: You know your present phone number but not your previous one
      • Evaluation
        • Strong laboratory support
        • Suffers as a general theory as the situations it best deals are rarely encountered in everyday life
        • Lack ecological validity
        • Studies of interference have largely involved episodic memory


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