Similarity of Materials:
The similarity between the two sets of materials influences the degree of interference. The general principle is that the greater the similarity between the original and the interpolated materials, the greater the interference.
Interference primarily comes from similar memories. The Skaggs-Robinson hypothesis states, “As similarity between interpolated and original learning is reduced from a near identity, retention falls to a minimum and then rises, but with decrease in similarity it never reaches the level obtained the maximum similarity.” When the two activities are completely dissimilar, -ere is less confusion, and therefore, less retrieval failure.
Meaningfulness of Materials:
Meaningless materials are more likely to be forgotten than meaningful materials. Meaningful materials evoke associational linkage with subjects’ personal knowledge and experiences. They are, thus, related to a few familiar cues.
A person can fall back on these cues at the time of recall. But meaningless materials do not carry any associational links with person’s store of knowledge in the LTM. That is why it is more difficult to memorize nonsense syllables such as ZOQ, QIX, and KEZ than the meaningful words like KEY, SUN, and PIG. If both original and interpolated materials are meaningless, retrieval failure would be more.
Nature of the Interpolated Task:
The more difficult the interpolated task, the more it will interfere with the memory of materials learned earlier. If you study a course on psychology, and then a course on anthropology for the examination, the contents of anthropology would interfere more with the memory for psychology. If the interpolated task were simpler such as cleaning clothes, you would experience less interference with memory for psychology. If the interpolated activity has emotional content, forgetting will be more.
The temporal location of the interpolated task is also another important factor. Interpolated task given just after learning or just before the recall heightens the influence of retroactive interference. Minimum interference occurs if the interpolated task is introduced in the middle of a long retention interval.