Explanations for Forgetting: Interference

What is the interference theory?

When one memory prevents the retrieval of another memory, causing forgetting or distorted perceptions of these memories. This happens especially more if the memories are similar (same type of information, same subject, same format) because they’re more likely to get mixed up.

Where does interference normally take place?

In the LTM. Once information has reached the LTM, it’s basically permanent. Therefore, any forgetting of LTMs is most likely because we can’t get access to them even though they’re available.

What does interference do?

It makes it harder for us to locate LTMs even though they’re available, and this is explained as ‘forgetting’.

What are the types of interference?

• Proactive interference

• Retroactive interference

What is proactive interference?

When older memory interferes with a newer one (pro in this context means working forwards, from old to new).

• Example: the names of previous neighbours are remembered instead of the names of the new neighbours who have just moved in

What is retroactive interference?

When newer memory interferes with an older one (retro meaning working backwards, from new to old).

• Example: the names of new neighbours who have just moved in are remembered but the names of previous neighbours are forgotten

What did Keppel & Underwood (1962) argue about Peterson & Peterson’s trigram experiment findings?

In the experiment, participants remembered the trigrams presented first despite interval length, found it harder to recall later trigrams

• Proactive interference had occurred as memory from earlier trigrams (which transferred to LTM) interfered with memory for new trigrams because of similarity of info

What was the procedure of McGeoch & McDonald (1931) study in terms of effects of similarity: retroactive interference?

• Participants given a list of 10 adjectives to learn until they feel confident they could recall it with 100% accuracy (List A = the original list)

• After a 10 minute rest, each participant was given a second list to learn — but the type of second list varied by group. They were randomly assigned to one of these six conditions:

1. Synonyms

2. Antonyms

3. Words unrelated to the original ones

4. Consonant syllables (e.g. BAP, MEC)

5. three-digit numbers

6. No new list - these participants just rested (control condition)

What were the results of McGeoch & McDonald’s (1931) study in terms of effects of similarity: retroactive interference?

• Recall of the original list (List A) depended on how similar the second list was

- The worst recall (most forgetting) occurred in the group that learned synonyms (most similar meanings)

- The best recall (least forgetting) occurred in the group that learned numbers and consonant syllables (least similar).

- The control group (no second list) showed very little forgetting

• So: More similarity → more interference → worse recall

What did McGeoch & McDonald (1931) conclude from their study in terms of effects of similarity: retroactive interference?

• Supports retroactive interference

• New information that resembles old information interferes with and disrupts the ability to recall the original memory

• Interference is stronger when the degree of similarity between items is greater

What was the procedure of Baddeley & Hitch (1977) experiment in terms of retroactive interference in the real world?

Field experiment, Quasi experiment

• Asked Rugby players to recall the names of the teams they played with earlier in the season in order (players had played a different number of games due to injuries, being dropped etc.)

- Condition 1: Participants who played every match in the season

- Condition 2: Participants who missed some games

What were the results of Baddeley & Hitch’s (1977) experiment in terms of retroactive interference in the real world?

• Players who had played the most games forgot proportionally more names than those who had played fewer games

• Recall was better for players who had played fewer matches, even if the match was from a long time ago

What did Baddeley & Hitch (1977) conclude from their experiment in terms of retroactive interference in the real world?

The learning of new team names interfered with the memory of older team names, supporting retroactive interferences

• Shows retroactive interference occurs in real life, not just in labs.

• This supports the idea that forgetting is heavily influenced by interference, not just decay over time

What was the procedure for Tulving & Psota (1971) experiment in terms of Interference?

Lab experiment, repeated measures design

• Participants were given lists of words organised into categories, one list a time (participants weren’t told what the categories were)

• They learned several lists one after another, which should create proactive interference (earlier lists interfering with later ones)

• After learning, participants were tested in two different recall conditions:

  • Free recall (just recall as many words as possible)

  • Cued recall (given the category names as cues to help retrieval)

What were the results of Tulving & Psota (1971) experiment in terms of Interference?

• Free recall:

  • Recall got worse the more lists they learned

  • This shows proactive interference building up

• Cued recall:

  • When given the category names, recall of the words significantly improved, even for later lists (recall interference effects disappeared) - remembered 70% of words

  • This shows that the information wasn’t gone — the cues helped access it

What was did Tulving & Psota (1971) conclude from their experiment in terms of Interference?

• Forgetting was partly due to proactive interference, because earlier learning disrupted recall of later lists

• But the large improvement with cues shows that a lot of the “forgotten” information was still stored — it was a retrieval failure, fixed by providing the right cues

What are the strengths of Interference as an explanation for forgetting?

• Real world support

- Baddeley & Hitch rugby experiment shows interference has an effect in everyday situations

• Lots of supporting evidence

- Many well-controlled lab studies (e.g. McGeoch & McDonald) consistently show both proactive and retroactive interference → reliable explanation

• Predictable effects

- Interference is strongest when memories are similar, giving the theory strong predictive power

What are the weaknesses of interference as an explanation for forgetting?

• Effects of interference disappear when faced with cues showing that interference only causes forgetting when stimulus is doing free call

- Because the memories aren't lost — they’re just harder to access. Retrieval cues (like category names) unblock access, so interference only causes forgetting during free recall, not when effective cues are provided

- Supported by Tulving & Psota experiment (1971)

• Interference is a partial explanation for forgetting

- Conditions needed for interference forgetting is rare, much of the evidence is lab based, so researcher can create ideal conditions for interference

• Two memories usually have to be similar to interfere with each other, doesn’t happen very often (it could but not a lot)

- So forgetting is better explained by other theories