Memory

Forgetting

• Is forgetting losing information or simply not being able to recall it?

• How can you tell the difference?

• When was the last time you forgot something?

• Had you forgotten or was it failure to recall?

• What type of information are you more likely to forget? (names/dates/faces/facts/numbers/conversations/experiences etc)

• Think about when you forget. Are you more likely to forget in a particular situation or specific emotional state?

Starter Questions

• Assumes that memory traces are created during encoding (physical existence)

• Lack of rehearsal means that this trace slowly disappears (decays).

• Explains why things are forgotten over time.

• This deals with forgetting due to lack of availability not lack of recall (the memory is not there)

• Hebb (1949) argues that during learning that the trace which is formed is timid and fragile. With learning (repetition), it grows stronger until a constant trace is formed through neurochemical and neuroanatomical changes. According to the theory, short term forgetfulness happens because the active trace is disturbed.

Forgetting in STM – Trace Decay

• STM has limited capacity so when we take in new information it pushes other information out.

Forgetting in STM – Displacement Theory

• Peterson & Peterson (1959). In terms of decay theory, the trace could not grow stronger and so broke down. OR as ppts were counting the information could just have been displaced.

• Reitman (1974) During retention interval ppts asked to listen out for a tone rather than being given new info. During a 15 second interval word recall fell by 24%. Trace decay? OR were ppts thinking about what to have for dinner? Counting the tiles on the wall?

Research

Aim: to test if forgetting in STM is due to trace decay or displacement.

M&P: 4 students – 90 x 16 digit lists and asked to recall the number which came before the first occurrence of a probe number. 2 conditions (individual groups) A – were given the list at a fast pace (4 digits per second)

B – given the list at a slow pace (1 digit per second) – trace decay

If forgetting was a result of trace decay then group B would have lower results. If forgetting is a result of displacement then there would be no difference in results.

Results: Found that recall was better when recalling from the end of the list – supporting displacement theory.

Waugh and Norman (1965) (see handout)

• Same theory as decay theory in STM but that the decay is much more likely to be a result of brain damage.

• Lashley (1931) trained rats to learn mazes then removed parts of their brains. Correlation between amount removed and amount of forgetting. Evidence for physical decay.

•Very little evidence to definitively support this theory.

Decay Theory - LTM

• Proactive interference – when past learning interferes with attempts to learn something new. (Old memories disrupt new ones)

• Retroactive interference – when current learning interferes with old learning. (New memories disrupt old ones)

• Eg – learning new mobile numbers. Keep giving out your old number – proactive interference.

• If that number was only temporary and you need to go back to giving out your original number but give out the temp number – retroactive interference

• The information has to be similar in order for interference to occur – studying 2 languages, places, times, numbers etc

Interference Theory - LTM

• Lab experiments – lacks mundane realism/ecological validity

•Extent to which this theory can be attributed to forgetting remains unclear.

Interference Theory

• This theory assumes that forgetting is a result of lack of retrieval (memory is available but not accessible)

•2 types of cues that can trigger memories:• Context dependent forgetting (external)• Abernethy (1940) • cues from our environment help us remember (songs, smells, places, etc)

• State-dependent forgetting (internal) • Goodwin et al (1969); Hardman (1998)•When the physical/emotional state we are in triggers a memory. (stress, drunk, happy, etc)

Cue-dependent forgetting - LTM

•Lab experiments – lacks mundane realism

• Procedural memory?

Cue-dependent forgetting

•Tulving and Psotka, 1971

•Ppts given 6 lists of 24 words each divided into 6 categories.

•After each list ppts to free recall the words they could remember.

•Results showed that the participants who had been given all 6 lists performed worse than other participants who were only given 1 or 2 lists. This is evidence for retroactive interference.

•After they free recalled the final list they were then asked to recall all the words from all the lists but were given the category names (cued recall).

•The cued recall test found that all participants recalled, on average, 70% of the words they had been given – interference disappeared.

•Conclusions – interference effects mask what is available – the information is there it’s just more difficult to retrieve. Forgetting is a result of retrieval issues not encoding.

Interference or lack of cues?

• Psychoanalytical approach

•Wanting to forget either:•Consciously (suppression)•Unconsciously (repression)

• You may want to consciously forget something because you just don’t want to do it eg when you have been asked to do the dishes, tidy your room, homework, etc

Motivated Forgetting

• Freud’s theory that the ego is trying to protect itself from an emotional conflict.

• The traumatic memory is pushed into the unconscious in order to protect the individual. This memory can, however, still affect the conscious mind.

• Can be recovered during RMT.

• False memories?

Repression

Repressed traumatic memory

Conscious mind

Unconscious mind

• Bradley and Baddeley, 1990, word association task – ppts found it more difficult to remember what their responses were to emotionally charged words than to neutral words straight away but could recall them better over time. Strong emotions suppress SMT but enhance LMT OR strong emotions are initially repressed but disappears over time?

• Williams, 1994 – 38% couldn’t recall being sexually abused. 16% who did claimed that the memory had been recovered. No memory of childhood abuse is common and that recovery is possible.

•Karon and Widener, 1997 – WWII veterans – mental illness alleviated when painful memories were recovered in therapy.

Research