Explanations of forgetting

Concept of forgetting refers to person's loss of ability to recall a thing that they have previously learned 

There are explanations to why this may happen in both the STM and LTM

One explanation is decay theory
Physical representation of info in brain is referred to as a memory trace/engram
Suggested trace simply decays if not rehearsed - rehearsal strengthens connections between neurons
Explains results of trigram study by Peterson & Peterson - no rehearsal so info disappeared from STM in 18 secs at most 

Second explanation - new set of info physically overwrites the older set, disaplcing it completely

Happens because STM has limited capacity
If full and new info is presented all that can happen is displacement 

Peterson & Peterson found STM lasts 20 secs suggesting it decays but consonant cluster may have been displaced with the counting which was used as a way of preventing rehearsal

Waugh & Norman (1965) - used serial probe technique 
Ps recalled number following a probe more accurately if near end of list - fewer numbers after to displace it
Recall also better for numbers presented quickly - explained by decay - although displacement more significant, decay does contribute to forgetting too.

Forgetting in LTM also explained by decay theory 

Individuals who suffer brain damage could loose memory due to complete loss of memory traces

Lashley (1931) - trained rats to learn mazes then removed sections of their brains

More brain that he removed, the more the maze was forgotten - supports physical decay of memory 

In 1950s , interference theory was theory of forgetting

Proactive interference is when past learning interferes with new memories, causing forgetting

Reteroactive interference is when new learning interferes with old memories, causing forgetting

Underwood (1957) - compared recall of consecutivelt learned word lists

Old lists inhabired reall of new ones (proactive) and new lists the recall of old (reteroactive)

Cue dependent forgetting is final explanation of loss of LTM

Memories may be avaliable but not accessible due to lack of cues 

Context-dependent forgetting happens if external cues (people places) that were present dueing learning disappear
Abernethy (1940) - students tested by same instructor and in same room when they learned the course had better recall than if cues were absent

State-dependent forgetting happens if internal cues/mood that were present during learning are different at time of recall
Goodwin et al (1969) - sober people forgot where they'd put things when drunk but remembered when drunk again

Baddeley & Hitch (1977) - natural experiment supported interference rather than decay theory
Rugby players who played more games forgot more about the games over the season but if decay theory was true they'd all remember the same as it would be the same time causing them to forget

Tulving & Psotka (1971) - learning more lists worsents recall of them (reteroactive interference)
However, if recall cued there is no difference - suggests info is avaliable but inaccessible so interference must occur during retrival