Explanations of forgetting
Trace Decay
 Information from the STM leaves a trace in the brain due to the excitation of nerve cells.
 This neural activity gradually dies away unless the material is rehearsed.
 Hebb (1949) argued while learning is taking place, the engram – a permanent change in
neural tissue, in the brain, that represents what has been learned – which will eventually be
formed is delicate and liable to disruption because it is an active trace.
 With learning, it grows stronger until it is permanent.
 If it is not used/practised, the engram will decay.
 It can only apply to STM because when we rehearse material the corresponding neural
activity causes a structural change in the brain.
 Evaluation:
o It is difficult to test trace decay because if participants are tested after different time
periods they could be rehearsing and thus strengthening the trace; but if prevented
– distracter task – forgetting could be due to interference from the task rather than
decay of the memory trace.
o Has difficulty dealing with situations where items which cannot be remembered at
one time can be remembered at a future time, even though no additional
presentations have been made. If the trace has decayed it should never be available.
o Peterson and Peterson found that after 18 seconds the trace almost completely
decayed when rehearsal is prevented.
Displacement theory
 Explains forgetting from STM in terms of the limited capacity of this store.
 Suggests a limited number of ‘slots’ for information – around 7 (Miller).
 When system is full – oldest are ‘pushed out’ or displaced by incoming information.
 Waugh and Norman (1965) found if the probe was one of the digits at the beginning of the
list, recall was smaller because later digits displaced earlier ones. However, if the probe was
towards the end, recall was high since last digits were still available to STM.
 Evaluation:
o Gives adequate account of forgetting from STM when applied to the multi-store
model.
o More recent models – working model – indicated STM is more complex.
Interference Theory
 Concerns what occurs before, during and after learning.
 At the beginning, interference can prevent information from passing to STM to LTM.
 Two types of interference:
o Proactive interference – earlier learning interferes with what you are trying to learn
at present. E.g. if you learnt Spanish and how have difficulty learning French.
o Retroactive interference – more recent learning interferes with the recall of earlier
material. E.g. you know your present mobile number but cannot remember your old
one.
 Evaluation:
o Strongest support comes from laboratory studies such as Keppel and Underwood.
o But these tend to use nonsense syllables as stimulus during laboratory studies.
o When meaningful material is used, interference is more difficult to prove.
o Suffers as a general theory as the situations it best deals with are rarely encountered
in real life.
o Most studies lack ecological validity.
Lack of consolidation
 Time dependant changes occur in the nervous system as a result of learning.
 In order for information in STM to become an LTM it must go through a process called
consolidation.
 During consolidation, STM is repeatedly activated, if something interrupts it then STM
cannot be consolidated and memories cannot be ‘stored’ for long-term access.
 Evaluation:
o Patients who have been concussed often suffer retrograde amnesia, which is loss of
memory for events prior to concussion. This may be because the consolidation
process has been interrupted.
o Electro-convulsive therapy (ECT) causes memory loss just before therapy is given.
Evidence suggests that after a one-hour delay between learning and ECT, perfect
retention occurs. Suggesting that the essential consolidation period required, to
ensure information reaches long-term store, is up to one hour. There is evidence to
support the theory that a consolidation process is necessary to prevent memory
disruption and loss.
Retrieval Failure Theory
 Memories cannot be recalled because the correct retrieval cues are not being used.
 The role of role of retrieval cues is demonstrated by the ‘tip of the tongue’ phenomenon, in
which we know we know something but cannot retrieve it from the LTM at that moment.
 Use of environmental cues to aid memory.
 Tulving (1972)
o Investigated retrieval failure in LTM.
o Gave participants a list of words, and then asked them to write down as many as
they could remember in any order.
o Later participants were asked to recall them a second and then third time.
o He found that not all of the same words were recalled across all occasions, and one
word was recalled on the third occasion that had not been recalled earlier.
o Cannot be explained by trace decay because it would never be available.
o But retrieval failure would argue that different retrieval cues were used which
resulted in different recall.
o Used ‘cue-dependent forgetting’ to explain that if the same cues are not present at
recall as during the original learning, then recall is poor.
 There are two types of cue-dependent forgetting:
o Context-depending forgetting – occurs if relevant environmental variables were
present when learning took place are missing at recall; they act as external clues.
o State-dependent forgetting – occurs in the absence of relevant psychological or
physiological variables that were present during learning; they act as internal clues.
Happy at learning – happy at recall; was matched.
 Evaluation:
o Able to explain findings that cannot be explained by trace decay theory.
o Empirical evidence to support cue-dependent forgetting.
o Some studies were taken out in extreme conditions, which makes them lack
ecological validity.
Motivated forgetting theory
 May have nothing to do with interference from other items, or failure to consolidate
material, but in fact we are motivated to forget.
 Freud (1901) some experiences are so painful that if allowed to enter consciousness we
would become overwhelmed with anxiety.
 Therefore, they are repressed and stored in the unconscious to become inaccessible.
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Even when a person seems to be remembering, they change the subject to stop the painful
memory.
The original experience has been stored but is now inaccessible.
Glucksberg and Lloyd (1967)
o Aim: to investigate motivated forgetting.
o Method: in a repeated measures design experiment, participants required to learn a
paired-associate list of words (A-B). Then asked to read a second list of words some
of which were related to B words on the paired-associate list. The related words on
second list accompanied by an unexpected and unavoidable electric shock.
Participants then asked to recall the original list.
o Results: B words that were related to the second list were forgotten significantly
more than control words.
o Conclusion: Supports motivated forgetting theory as the words accompanied with a
shock had unpleasant associations and would have been repressed.
o Evaluation: Ethical implications such as deception and electric shocks. Also a
contrived study as motivated forgetting is usually concerned with personal and
emotional events.
Evaluation:
o In order to investigate it in the laboratory, participants would have to experience
something traumatic which is unethical.
o Support is evident in tests of emotional inhibition – Levinger and Clark (1961) found
participants were particularly poor at remembering associations to emotional
words, e.g. anger.
o More recent studies found it may not be repression but arousal that influences
recall of emotionally charged words.
Short-term memory
Decay
Displacement
Short-term and long-term
memory
Interference
Decay
Long-term memory
Interference
Lack or consolidation
Retrieval failure
Motivated forgetting
Key Points:
 Trace decay explains forgetting as the fading of neurological trace which is formed when a
stimulus is encoded.
 Displacement is based on the limited capacity of STM because when the seven ‘slots’ are
full, new information pushes out the oldest information in short-term store.
 Retrieval failure is concerned with cues, both internal and external, which aid retrieval of
memories. However, the research into retrieval failure has often involved extreme
conditions and therefore has lacked ecological validity.
 There are two types of interference: retroactive and proactive. Support for interference
theory of forgetting comes largely from laboratory studies and these may not be relevant to
forgetting in real life.
 Lack of consolidation as a theory of forgetting refers to the necessary period of time
required so that memories can be ‘embedded’ in long-term store, and if disruption occurs
during the consolidation period then memories of events just prior to the incident are lost.
 Motivated forgetting refers to Freud’s theory of repression, which is when anxiety-provoking
material is pushed into the unconscious and becomes inaccessible.