Forgetting

Forgetting

Forgetting is the inability to retrieve information that was previously stored. Psychologists have identified different explanations for why we forget, and whether the information is lost from STM or LTM.

Forgetting in STM: Displacement and Decay

Displacement Theory

• STM has a limited capacity (7 ± 2 items — Miller, 1956)
• When STM is full, new information pushes out (displaces) old information to make room
• The displaced information is lost if it has not been rehearsed into LTM

Key study — Murdock (1962) — Serial Position Effect:

• Participants were given a list of words and asked to recall them in any order
• They remembered words from the beginning of the list (primacy effect — rehearsed into LTM) and the end (recency effect — still in STM)
• Words from the middle were forgotten — they had been displaced from STM by later words before being rehearsed into LTM

Decay Theory

• Memories in STM have a trace that fades over time if not rehearsed
• Without rehearsal, the memory trace simply decays and disappears
• Peterson and Peterson (1959): participants remembered trigrams (e.g. BVM) for 3 seconds but only about 10% after 18 seconds when prevented from rehearsing — supporting rapid decay in STM

Forgetting in LTM: Interference

Interference occurs when one memory disrupts the recall of another, similar memory. There are two types:

Type	Definition	Example
Proactive interference	Old memories interfere with the recall of new memories	You learned French at primary school; now you accidentally use French words when trying to speak Spanish
Retroactive interference	New memories interfere with the recall of old memories	After learning your new phone number, you can no longer remember your old one

Key study — McGeoch and McDonald (1931):

• Participants learned a list of words, then learned a second list before being tested on the first
• The more similar the second list was to the first, the more forgetting occurred
• This supports interference theory — similar information causes the most confusion

Forgetting in LTM: Retrieval Failure

Retrieval failure theory suggests that information is still stored in LTM but cannot be accessed because the right cue is missing.

• Cue-dependent forgetting — memories are linked to cues (context, mood, state) present at the time of learning. Without the right cue, the memory cannot be retrieved
• Context-dependent forgetting — better recall when in the same environment as when the memory was formed
• State-dependent forgetting — better recall when in the same emotional or physical state as when the memory was formed

Key study — Godden and Baddeley (1975):

• Divers learned word lists either on land or underwater, then recalled them in the same or different environment
• Recall was 40% better when learning and recall environments matched
• Supports context-dependent retrieval failure — the environment acts as a cue

Strengths and Weaknesses of Forgetting Theories

Theory	Strengths	Weaknesses
Interference	Lab studies provide controlled evidence; explains everyday forgetting of similar information	Lab tasks are artificial — may not reflect real-life forgetting; does not explain all forgetting
Retrieval failure	Strong research support (Godden & Baddeley); explains tip-of-the-tongue phenomenon; has real-world applications (context reinstatement in police interviews)	Difficult to prove a memory is stored but inaccessible (rather than truly lost); cues do not always work

Exam Tips

• Know the difference between interference (LTM) and displacement (STM)
• Be able to distinguish proactive from retroactive interference — direction matters
• Use Godden and Baddeley (1975) for retrieval failure — it is the key study
• For AO3: discuss whether forgetting is due to loss of the memory or failure to access it
• Link to real life: why revision in the same room as the exam might help (context cues)