Trace DecayTrace Decay

Trace decayTrace decay The theory suggests that learning causes a The theory suggests that learning causes a

physical changephysical change in the neural network of the in the neural network of the memory system, creating a memory trace or memory system, creating a memory trace or “engram”“engram”

Hebb (1949) looked at the brain and showed Hebb (1949) looked at the brain and showed that a memory occurs when a group of nerve that a memory occurs when a group of nerve cells excite (stimulate) one anothercells excite (stimulate) one another

www.

psyc

hlot

ron.

org.

uk

engram

noun

a postulated biochemical change (presumably in neural tissue) that represents a memory

EngramEngram = biochemical change (presumably in neural tissue) that = biochemical change (presumably in neural tissue) that represents a memoryrepresents a memory

Once this memory trace has been created, Once this memory trace has been created, it must be reinforced through repetition to it must be reinforced through repetition to strengthen it strengthen it

If the trace is If the trace is not reinforcednot reinforced by practice it by practice it will simply will simply weakenweaken and and decaydecay, causing , causing forgetting to occur. We need to use it or forgetting to occur. We need to use it or lose it!lose it!

Trace Decay (STM)Trace Decay (STM)

www.

psyc

hlot

ron.

org.

uk

So, trace decay explains forgetting as a So, trace decay explains forgetting as a problem of problem of availabilityavailability – that is, the – that is, the information is information is lost completelylost completely from the from the memory system through disuse and memory system through disuse and passage of timepassage of time

Biological processes in the brain cause the Biological processes in the brain cause the trace to decay until eventually the message trace to decay until eventually the message it carried, is lostit carried, is lost

Evaluating the trace decay theory Evaluating the trace decay theory of forgetting – AO2 pointsof forgetting – AO2 points

- The problem is that we The problem is that we dodo recall things we recall things we have not thought about for a long time. For have not thought about for a long time. For example we can ride a bike after a long example we can ride a bike after a long period. We have not been renewing the period. We have not been renewing the physical memories in the meantime, but the physical memories in the meantime, but the memory is still there.memory is still there.

- Sometimes, after being presented the right Sometimes, after being presented the right cues, memories are triggered and long-cues, memories are triggered and long-forgotten memories rememberedforgotten memories remembered

- Many elderly people can recall incidents from their youth Many elderly people can recall incidents from their youth in great detail. Unless they have recalled the instance in great detail. Unless they have recalled the instance many times throughout their lives, the trace should have many times throughout their lives, the trace should have decayeddecayed

- If the trace decay theory is correct, and you hadn’t If the trace decay theory is correct, and you hadn’t played the guitar for 20 years then not only would you be played the guitar for 20 years then not only would you be unable to recall the chord sequence for a particular song, unable to recall the chord sequence for a particular song, but it would also take you as long to learn the song the but it would also take you as long to learn the song the second time as it did the first. This simply isn’t true.second time as it did the first. This simply isn’t true.

- People under hypnosis can often recall things that they People under hypnosis can often recall things that they haven’t thought about for years, so their traces may still haven’t thought about for years, so their traces may still be therebe there

- Trace decay cannot explain why some people seem to Trace decay cannot explain why some people seem to have have poor recallpoor recall of even of even recentrecent events, while others events, while others have have incredible memoriesincredible memories going going back for decadesback for decades. Why . Why are there these huge individual differences?are there these huge individual differences?

Trace DecayTrace Decay+ Peterson & Peterson (1959)+ Peterson & Peterson (1959)

Had participants recall trigrams after varying intervalsHad participants recall trigrams after varying intervals During rehearsal an Interference task was given (counting During rehearsal an Interference task was given (counting

backwards in threes) to prevent rehearsalbackwards in threes) to prevent rehearsal They found less that 10% of information was recalled after 18 They found less that 10% of information was recalled after 18

secondsseconds This is evidence for trace decay in STM. Participants weren’t This is evidence for trace decay in STM. Participants weren’t

able to practice/repeat the information/memory, and so the able to practice/repeat the information/memory, and so the memory traces decayedmemory traces decayed

- However, this was a laboratory experiment, so the study - However, this was a laboratory experiment, so the study involved artificial tasks and an unnatural setting, and involved artificial tasks and an unnatural setting, and therefore lacked ecological validity. So the results may therefore lacked ecological validity. So the results may not be valid for the “real world”, and therefore this study not be valid for the “real world”, and therefore this study cannot support the trace decay theory of forgettingcannot support the trace decay theory of forgetting

www.

psyc

hlot

ron.

org.

uk