Forgetting: Interference & Retrieval Failure

Why do we forget? The AQA specification focuses on two main explanations: interference theory (which explains forgetting from LTM) and retrieval failure (also known as cue-dependent forgetting). Understanding these theories, the evidence that supports them, and their limitations is essential for exam success.

Key Definition: Forgetting is the inability to recall or recognise information that has been previously learned. It may be due to the information being lost (unavailable) or being temporarily inaccessible (available but not retrievable).

---

Interference Theory

Interference theory proposes that forgetting occurs because similar memories compete with and disrupt each other. The more similar the memories, the greater the interference. There are two types:

Proactive Interference (PI)

Key Definition: Proactive interference occurs when old (previously learned) information interferes with the ability to recall new information. The old learning disrupts new learning.

Example: You change your phone password, but you keep entering the old password instead of the new one. The old memory proactively interferes with retrieval of the new one.

Direction: Old → disrupts → New

Retroactive Interference (RI)

Key Definition: Retroactive interference occurs when new (recently learned) information interferes with the ability to recall old information. The new learning disrupts old learning.

Example: After learning your new phone password, you can no longer remember the old one. The new memory retroactively interferes with retrieval of the old one.

Direction: New → disrupts → Old

Summary Diagram

graph LR
    subgraph Proactive Interference
        A["Old learning"] -->|Disrupts| B["New learning"]
    end
    subgraph Retroactive Interference
        C["New learning"] -->|Disrupts| D["Old learning"]
    end

---

Research Evidence for Interference

McGeoch & McDonald (1931)

This study investigated the effect of similarity on retroactive interference.

Procedure:

• Participants learned a list of 10 adjectives until they could recall them perfectly.
• They were then given an intervening task before being tested on the original list.
• Six groups were given different intervening tasks, varying in similarity to the original list.

Findings:

Intervening Task	Similarity to Original	Mean Recall of Original List
Synonyms (e.g., "happy" for "joyful")	Most similar	12.5% (most forgetting)
Antonyms	Similar	18.0%
Unrelated adjectives	Somewhat similar	21.7%
Nonsense syllables	Low similarity	26.0%
Three-digit numbers	Very low similarity	37.3%
No intervening task (rest)	No interference	45.0% (least forgetting)

Conclusion: The more similar the intervening material to the original, the greater the retroactive interference. This demonstrates that interference is strongest when competing memories are similar.

Underwood (1957)

Underwood investigated proactive interference by reviewing previous studies of memory.

Findings:

• Participants who had previously learned many lists of words forgot more from the latest list than those who had learned fewer previous lists.
• After learning 10 or more previous lists, recall of the most recent list dropped to about 20% after 24 hours.
• After learning only one list (no previous lists), recall was about 70% after 24 hours.

Conclusion: The more previous material a person has learned, the greater the proactive interference on new learning. Forgetting is not just about the passage of time but about the accumulation of competing memories.

---

Retrieval Failure: Cue-Dependent Forgetting

Retrieval failure theory proposes that information is not lost from LTM but is inaccessible because the appropriate retrieval cues are absent. The memory is available but cannot be retrieved without the right cue.

Encoding Specificity Principle (Tulving & Thomson, 1973)

Key Definition: The Encoding Specificity Principle states that a cue will be effective in aiding retrieval only if it was present at the time of encoding. If the cues at retrieval match the cues at encoding, recall is improved.

There are two main types of cue-dependent forgetting:

Context-Dependent Forgetting

Forgetting that occurs when the external environment at retrieval is different from the environment at encoding.

Key Study — Godden & Baddeley (1975):

• Participants: Deep-sea divers.
• Procedure: Divers learned a list of words in one of two environments — on land or underwater — and then recalled them in either the same or a different environment.
• Design: Four conditions: learn on land/recall on land, learn on land/recall underwater, learn underwater/recall underwater, learn underwater/recall on land.

Condition	Result
Same environment (land–land or water–water)	Better recall
Different environment (land–water or water–land)	40% worse recall