Interference

Interference

Forgetting because one memory blocks another, causing one or both memories to be distorted or forgotten

Proactive interference

Forgetting occurs when older memories, already stores, disrupt the recall of newer memories.

The degree of forgetting is greater when the memories are similar

E.g. Giving your old phone number to someone after changing to a new one.

Retroactive interference

Forgetting occurs when newer memories disrupt the recall of older memories already stored.

The degree of forgetting is greater when memories are similar.

E.g. A teacher learning the student names of a new class may have trouble remembering the student names of an older class

McGeoch and McDonald 1931

Studied retroactive interference by changing the amount of similarity between 2 sets of materials.

Participants had to learn a list of 10 words until they could remember them 100% accuracy.

There were 6 groups of participants who had to learn different types of new lists:

1. Synonyms

2. Antonyms

3. Words unrelated to original list

4. Consonant syllables

5. 3-digit syllables

6. No new list (control condition)

Found that when participants were asked to recall the original lists of words, the group with synonyms had the worst recall. Shows that interference is strongest when the memories are similar.

Supports both types of interference.

Explanation of effects of similarity

2 possible reasons why similarity affects recall.

Could be due to PI - previously stored information makes new similar information more difficult to store.

Or it could be due to RI - new information overwrites previous similar memories because of similarity

Keepel and Underwood

Conducted the same study as Peterson and Peterson

Gave participants a trigram to remember and before recalling the trigram asked them to count backwards in threes. The length of time they were asked to count for gradually increased

Noticed that the number of trigrams recalled decreased with the greater length of time spent on the counting task

Concluded that proactive interference could explain this effect as the earlier memory of the trigrams had entered LTM and was interfering with the learning of new trigrams.

Schmidt 2000

Investigated how retroactive interference affects the ability to remember street names learnt in childhood.

More than 200 participants ranging from 11-79 years old were selected randomly from a database of former students of a Dutch primary school

Sent a questionnaire asking how many times they have moved, where they lived and how long for.

Also sent a map of the neighbourhood where they had lived where the street names were replaced with numbers

Amount of interference was measured by the number of times participants have moved to other neighbourhoods

Positive association between the number of times someone had moved and the number of street names they had forgotten.

Concluded that retroactive interference had occurred, where learning new street names had interfered with the ability to recall old ones.

Weakness of interference theory

Much of the supporting research has been conducted in laboratories.

For instance in the McDonald study, subjects are asked to learn numbers, syllables and word lists. This means it is low in ecological validity.

Using artificial tasks means the results cannot be generalised.

Memory in real life is about remembering birthdays and faces. So the theory lacks validity.

Baddeley and Hitch 1977

Asked rugby players to recall the names of the teams they had played against during a rugby season.

All players played for the same time intervals but some missed matches due to injury so interference was different in each player.

Players who played the most games and therefore had the most interference had the worst recall.

Shows that interference can operate in at least some real-world situations, increasing the validity of the theory.

Vogel 2005

Gave participants a series of tasks to test their working memory capacity.

Highest and lowest scores were given more tasks designed to create proactive interference.

Individuals with high WMC were less likely to be affected by PI than low WMC individuals.

Suggest that high WMC is associated with an enhanced filtering ability which helps prevent irrelevant information from disrupting working memory.

This makes high WMC individuals less susceptible to PI as they can maintain focus on relevant information more.

Tulving and Psotka 1971

Gave participants lists of words when the words were organised into categories.

Recall averaged about 70% for the first list but got worse for each additional list.

After the procedure the participants were given a cued recall test. Given the names of the categories. Recall rose to 70% again.

Shows that interference causes a temporarily loss of accessibility to material that is still in LTM. Not predicted by interference theory.