More generally, most of us tend to look back on the past in a generally positive way. Memories of college focus on football games, parties, and great lectures and not on fights with friends, frustrating homework assignments, and waitlists for popular courses.

Why do we generally focus on positive memories rather than negative ones? This question was explored in a paper in the November, 2012 issue of Psychological Science by Benjamin Storm and Tara Jobe. They point out that many people have a reasonably positive self-image. To keep up that self-image, it is helpful to focus on positive memories. In order to focus on positive memories, though, it is important both to promote your ability to retrieve positive information as well as to damp down or inhibit the negative memories.

Generally speaking, research on shows that retrieving information from memory involves both enhancing the information you want to retrieve as well as inhibiting competing memories. Storm and Jobe suggest that the more effective people are at inhibiting memories, the more that they will be biased toward positive memories of their past and away from negative memories.

To test the effectiveness of inhibition, they used a measure of retrieval induced forgetting. In this work was developed initially by Michael Anderson, Robert Bjork, and their colleagues. People first learn a set of pairings of related concepts (like fruit-banana, metal-silver, fruit-lemon, and metal-aluminum). Later, they are asked to complete some word stems that the retrieval of a particular pair they learned. For example, they might see fruit-le_____, where they are supposed to retrieve “lemon.” By retrieving “lemon,” they have to inhibit “banana.” Later, they are given another retrieval test. Some of the items on that test require them to retrieve something that had been inhibited before (so they get fruit-b_____ and have to recall the previously inhibited word “banana”) or something that had not been inhibited (like metal-s____ where they have to recall “silver”).

Previous research demonstrates consistently that people are worse at recalling words that were previously inhibited than words that had not been inhibited. The bigger the difference between people’s ability to recall words that were and were not inhibited, the more effective their inhibition systems. So, for each person in the study, the difference between their ability to recall words that were and were not inhibited was used as a measure of the effectiveness of their inhibition mechanisms in memory.

In three studies, Storm and Jobe correlated this measure of inhibition effectiveness with the ability to retrieve negative and positive memories of the past. To get people to retrieve memories, they were shown neutral words like “pool” or “medicine” and were asked to write down specific memories of events from their past. Some people were asked to focus on positive memories of the past while others were asked to focus on negative memories. In some of the studies, people were also asked to recall things either from the past month or from .

The measure of inhibition effectiveness was not strongly related to people’s ability to retrieve positive memories. However, this measure was reliably related to people’s ability to recall negative memories. The more effectively people inhibit information during retrieval, the less well they can remember negative memories.

This research demonstrates that we maintain our positive by trying to focus on positive memories of the past. People who happen to be better at inhibiting memories are better able to maintain this focus on positive aspects of the past.

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