Forgetting

Forgetting

1. Forgetting and Time

   • Forgetting increases as time progresses
   • Ebbinghaus 1913: used lists of nonsense syllables and tested himself over time - a logarithmic relationship between time and forgetting: we initially forget a lot, but over time the amount we forget decreases.
   • Meeter et al 2005: Looked at forgetting rates for people's memory for widely publicised events on TV and in newspapers (distinct, dateable events). Recall and recognition tested in 14,000 p's of different ages and countries using internet study. Recall dropped from 60-30% in the first year, followed by slower forgetting rates. Recall was worse than recognition

2. When do we forget?

   • Trace Decay
     • A memory trace is some physical change in the brain. Over time, If these traces are not used they may decay
     • What Decays? - A memory's activation may fade but the underlying memory is left intact or the memory's structural elements
     • Decay in LTM sometimes called "Disuse"
     • There is a biological basis of decay
     • People can recall memories that they thought were forgotten - trace decay is difficult to prove behaviourally
   • Interference
     • It is difficult to discriminate between similar memories. The number of similar traces will increase over time
     • Interference arises whenever the cue used to access a target becomes associated with other memories. E.G. 'what did you have for dinner 10 days ago'? - there are many memories between now and 10 days of having dinner interfering with memory for 10 days ago
     • Competition Assumption (Anderson et al 1994): A cue activates all of its associates to some degree and these "fight" one another. Interference increases with the number of competition a target has.
     • Cue-Overload Principle: Recall decreases with the number to be remembered items that are paired with the same cue
     • Retroactive Interference (RI): The tendency for more recently acquired info to impede retrieval of similar older memory - introducing a related second list of items impairs recall of the first list compared to a control condition; more training on the second list results in more first list impairments (Barnes & Underwood 1959)
     • Baddeley & Hitch 1977: Rugby players asked to recall the names of teams they played earlier in the season. Some players missed certain games, leaving a measure of forgetting due to decay as opposed to interference from intervening games. Time was not a good predictor of forgetting - forgetting increased with the number of intervening games.
     • Proactive Interference (PI): The tendency for older memories to interfere with the retrieval of more recent experiences and knowledge - PI effects more severe for recall rather than recognition.
   • Retrieval-Induced Forgetting (RIF)
     • Retrieval can harm recall of other memories related to the retrieved item.
     • In the real world, occurs in schools: Reviewing facts (Macrae & MacLeod 1999); Short answer and essay Qs (Carroll et al 2007); retrieving what we already know can contribute to forgetting.. Also occurs in the interrogation of witnesses (Shaw et al 2995): Learning phase - watch slideshow of a crime scene, Retrieval Practice Phase. - interrogated about some of the items in the slideshow, Result: interrogating people about some stolen items impaired their memory for related items.

3. Why do we forget? - Interference Mechanisms

   • Blocking: When a cue fails to elicit a target trace because it repeatedly elicits a stronger competitor leading people to abandon efforts to retrieve the target.
   • Inhibition: A reduction in the activity level of a contextually inappropriate response. Allows an unwanted response to be stopped and an alternative response to be executed. Results in LT difficulty in producing the inhibited response (e.g. trying to remember an old phone number). Inhibition predicts that RIF should generalise to new cues, thus exhibiting cue independence.

4. Reading: Wixted 2005

   • Forgetting is largely a function of nonspecific RI acting on memory traces that have not yet had a chance to consolidate. In the early stages of consolidation, memory traces are theoretically maintained by an LTP-like process in the hippocampus. However the maintenance of these traces is vulnerable to the subsequent induction of LTP-like processes associated with the formation of new memories,
   • Some very old evidence supports idea that a temporal gradient of RI is observed when memories are formed against background of mental quietude
   • Alcohol and benzodiazepines induce retrograde facilitation, but we don't know if a temporal gradient exists.

5. Reading: Anderson 2003

   • We should reconsider concept of interference as a learning phenomenon and reframe interference as arising from systems that achieve mental and behavioural control
   • Forgetting is not a passive effect of storing new memories, but results from inhibitory control mechanisms recruited to override prepotent responses.
   • 2 control situations in which response override is necessary: selection and stopping