When we think about memory, we often focus on situations in which we encounter some information and then recall it later. In many situations, though, after we encounter the information, we talk about it with other people. That creates a shared recollection. This can happen both socially and in situations.

Much less is known about shared recollection than about individual recall. Cognitive psychologists tend to focus mostly on what individual people do rather than groups of people, and so most memory studies involve individuals who study information and then remember it later.

A fascinating paper by Adam Congleton and Suparna Rajaram in the August, 2014 issue of the Journal of Experimental Psychology: General looked at factors relating to shared memory.

One observation from previous research on creating shared memories is that when groups work together to recall information, they remember less information overall than the individuals in the group would have remembered if they had worked alone. The idea is that the group discussion focuses the group members on a subset of the information they were exposed to, and that subset is smaller than what the individual group members would have thought about if they had not been part of a group.

In this study, participants in a room were exposed to 120 words on a screen. The words were chosen from 8 categories of objects, so that there would be some way for remembering one word to remind people of other words on the list. After a brief delay, all participants were asked to remember as many of the words as they could. Then, participants performed three more recall tests in that session and one additional test a week later.

Some participants worked alone in all of the remaining recall tests. The rest of the participants were put in groups of three. In one condition, the group did the second recall task together. In a second condition, the group did the third recall test together. In a fourth condition, the group did both the second and third recall tests together. The last recall test of the first day and the test a week later were all done individually. There were some subtle differences across these three group conditions, but I will gloss over those for now.

When the group did recall, they talked about the words they remembered, and one member of the group wrote down each word that the group remembered.

What happened?

Looking at the last recall session on the first day, groups of three individuals selected at random from the individual condition remembered more overall than the groups that recalled a list together. That is consistent with the previous findings that I mentioned.

Recalling in a group increased the similarity of what people from that group were able to remember. People in groups that worked together recalled more of the same items than people who recalled alone. In addition, they tended to remember the words in the same order. These findings suggest that working together as a group made everyone’s memory of the words more similar.

A particularly interesting result was that the groups that showed the most similarity at the end of the study (as measured both by the amount of overlap in what they remembered and the similarity of the order or recall) was related to the difficulty that groups have recalling information overall compared to individuals. Groups that remembered less when they worked together were more similar later than groups that remembered more when they worked together.

The idea is that when a group really works together, they influence each other’s memory. The idiosyncrasies of what they would remember drop away, and they end up with a shared memory of the set of words. So, everyone loses some details about the list, but they end up with a strong shared memory.

A similar pattern of results was observed after a one-week delay suggesting that working with the group influenced the of the list.

The researchers in this study used lists of words, because that is a convenient way of comparing memories across people. But, this work tells us something about memories in general. When we discuss an event with the people around us, it affects what all of us are able to remember later. Over time, the group’s memory for an event gets more similar, so that eventually all of the group members remember the same details about the event. Even though they may have experienced the event differently, recalling it with others makes everyone’s memory more similar.

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