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Mechanisms of forgetting
storage failure or retrieval failure?…
Mechanisms of forgetting
- storage failure or retrieval failure?
Encoding specificity
Tulving & Thomson (1973) Encoding specificity principle
- changes in context and state can impair memory as they remove relevant cues
- reinstating cues present at encoding during retrieval can improve memory
- fewer memory cues should be present at a longer retention interval because of context change = if you reinstate enough cues then it’s possible to retrieve a memory regardless of the retention interval e.g. shown by Wagenaar (1986)
= forgetting is due to retrieval failure, where a memory trace can be recovered if sufficient relevant cues are present
Retroactive interference
Bartlett's (1932) studies shown that memory is a reconstructive process, open to distortion --> does interfering info after an event cause that info to be forgotten? Either overwrites original memory trace (storage failure) or original memory trace is inhibited (retrieval failure)
- Mueller and Pilzecker (1900) one of the first empirical demonstrations of forgetting due to interference- p's less likely to recall a memory item if in the interim the retrieval cue used to test that item had become associated with another memory = known as retroactive interference, freq. demonstrated in lab studies
Effect of misleading info consistently demonstrated in studies of eyewitness testimony
- classic study by Loftus, Miller & Burns (1978) slides of car accident at a junction with stop sign. Immediate after viewing, event referred to occurring at either stop sign (control) or yield sign (misleading info). Forced-choice recognition test found p's misleading info tended to incorrectly report seeing yield sign in original scenes = misinformation effect
- replicated since by Takarangi et al. (2006) using video materials
- Critically, explained effect as caused by destructive updating --> permanently overwrites and replaces the original memory trace (storage failure account)
- McCloskey and Zaragoza (1985) challenged this: claim that RI occurs as p's don't notice and so do not encode the initial information= the misleading option presented to participants (i.e. yield sign) does not conflict with an already stored memory representation (i.e. stop sign), but rather simply fills a memory gap.
- Bekerian and Bowers (1983) found no evidence of a loss of original memories in a similar experimental design as Loftus et al. (1978) --> instead forgetting was attributed to an absence of critical cues at the time of retrieval that were present during initial encoding = in keeping with encoding specificity account
Retrieval-enhanced suggestibility
- Testing effect: if retrieval practice enhances memory of a witnessed event, then this enhancement would seem likely to reduce people’s susceptibility to misinformation.
- However, contrary to this, retrieval practice can sometimes increase the negative influence of misleading suggestions on eyewitness memory performance, a finding termed retrieval-enhanced suggestibility - Chan et al. (2009)
- RES effect has been reported in various procedures (e.g., Chan & Langley, 2011) but initial test used cued-recall, with questions asking specific details of the event
- Wilford et al. (2014) Initial testing after witnessed event (burglary) increased misinformation reporting on the final test for peripheral details (e.g., the type of car driven by a person, the color of the shirt worn by a person) in cued recall and free recall tests, but the effect was significant for central details only after aggregating the data from all conditions
= initial free recall can produce RES --> particular importance because most criminal investigations begin with free recall (not just after prompts)
Influence of emotions on retroactive interference/misleading info:
- positive affect is often taken as information to indicate that all is well (Bless and Bohner, 1991), producing suboptimal decisions
- evidenced by research on eyewitness testimonies, which demonstrates that subjects in a positive mood are more susceptible to misinformation (Forgas et al. 2005)
- -ve affect has different effect on misinformation:
-Thorley et al. (2016) compared the impact of negative and neutral moods during encoding and/or retrieval upon eyewitness recall of a non-emotive event. A negative mood during encoding had no impact upon the number of correct details recalled (provided participants were in a neutral mood at retrieval) but a negative mood during retrieval impaired the number of correct details recalled (provided participants were in a neutral mood at encoding). A negative mood at both time points enhanced the number of correct details recalled, demonstrating a mood-dependent memory enhancement. = it facilitates accurate memory recollection, if the negative mood was present at the time of encoding and retrieval.
-in line with research finding that negative affect promotes deliberation over decisions (Lambert, et al. 1997) and makes individuals focus on details rather than the big picture (Gasper & Clore, 2002).
Retrieval blocking
= later information (RI) blocks or inhibits the retrieval of earlier information when the potentially-interfering information is active in memory --> forgetting is not due to unlearning/fragmentation of memory traces but
Demonstrated in expts. by Chandler (1993):
- A-B target names (e.g., Robert Harris) and were given an immediate cued recall test (Robert H---?) to ensure that they had learned them.on a second list of names, which also had to be learned, there appeared A-C names (e.g., Robert Knight) that were similar to the earlier experimental names, but there were none on the second list that were similar to the earlier control names: instead, there were a number of unrelated D-E names.
- on a final memory test, participants were given a mixed-up list of the first names and surnames that had appeared in the original list (the A and B elements), and were asked to match them up.
- participants were able to correctly match 59% of the control names but only 46% of experimental names, representing a sizeable RI effect.
- Further expt. varied delay between 2 lists of names and the final memory test- 5,15 or 30 mins. As delay increased, RI decreased --> By 30 mins, there was no evidence of a RI effect= can't be explained by storage failure account because has to attribute the RI obtained at the shorter retention intervals to genuine unlearning of the original experimental items, at least relative to the control items; but if the experimental items have to some extent been unlearned, they should still be harder to recall than the control items at the 30 min delay.
Does this only apply to misleading verbal info?
- Windschitl (1996) reported no long-term RI using faces as stimuli.
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Consolidation
- various ‘amnestic’ treatments e.g. ECT, sleep deprivation, or hippocampal lesions can disrupt memory but that they tend to do so more for recent than for older memories.
- The standard consolidation model proposes that this comes about because memories depend on the hippocampus and other medial temporal lobe structures for a time-limited period. During this period, amnestic treatments which disrupt hippocampal function therefore impair the memories. With the passage of time, however, memories become independent of the hippocampus and consequently immune to the effects of amnestic treatments.
- Tempting to say that they are so permanent that they can't be disrupted in the same way as unconsolidated ones i.e. should be particularly resistant to forgetting
Re-consolidation suggests not immune to interference:
- Soeter and Kindt (2015) reactivated phobia-related memories in spider phobics by asking them to spend 2 min approaching a tarantula and then gave them either an amnestic drug (propranolol) or a placebo. For another control group the propranolol was administered without any memory reactivation. When tested at various intervals up to 1 year, fear was lower and approach easier in the group administered propranolol after memory reactivation. The results open up the possibility that long-consolidated harmful memories (e.g., in phobias or PTSD) can be partially or wholly eradicated by applying an amnestic treatment during the reconsolidation ‘window’.
- BUT, claims are controversial--> Hardwicke et al. (2016) reported several experiments failing to replicate a well-known motor memory reconsolidation finding, and Wood et al. (2015) likewise failed to replicate an earlier claim about eradicating trauma memories via disrupting reconsolidation in PTSD sufferers.