Before now, most research on the topic has followed what's known as a "think / no-think" paradigm, in which participants deliberately suppress their memory for certain words. They're shown a cue word and they deliberately don't think about the word it was previously paired with. This research has shown that people go on to have poorer memories for target words that they've deliberately suppressed. At least one study showed that this was especially the case for negatively valenced material; another found the opposite. These studies have provided a proof-of-principle, but deliberately forgetting a few words in a lab has little immediate relevance to real life.
Enter Saima Noreen and Malcolm MacLeod at the University of St Andrews, two researchers who have extended this line of research into the realm of autobiographical memory. They wanted to know if people could be trained to forget, not word pairs, but actual memories from their lives.
Across two studies the researchers used words like "barbecue" to prompt dozens of never-been-depressed students to recall real episodes (shorter than a day) from their lives and to describe them in as much detail as possible in one minute. These episodes were then paired with the initial prompt word and another cue word of the participants' choosing (for example, I'm making this up, but "barbecue/uncle" might have been paired with the memory of the time that the participant's uncle dropped his beer on the barbecue and ruined all the food). This reminiscence procedure was followed 24 times. Afterwards, the researchers made sure, through further testing and rehearsal, that every student had a good memory for all 24 word pairs and their associated autobiographical memories.
Next came the "think / no think" training phase - the students were presented with 16 of the word pairs from earlier, and for some of them they had to describe once again the relevant autobiographical memory in detail for 60 seconds; for others they had to deliberately not think of the relevant memory for four seconds. This procedure was repeated 16 times for each word pair and memory (the remaining 8 pairs and their memories were not part of this process and acted as baseline material).
Finally came the crucial recall phase. The participants were presented with all 24 of the word pairs and this time, for every pair, they had to describe in as much detail as possible the relevant autobiographical memories that went with them. Here's the key finding - the students' memories of the autobiographical memories they suppressed earlier in the "think / no think" phase were less detailed than their baseline autobiographical memories (the ones that were neither thought about or suppressed in that earlier phase). Note, the gist of the previously suppressed memories was unaffected, but they had about 11 per cent less detail on average. In the first variation of this study, this loss of detail was particularly striking for more negative autobiographical memories, but in a follow-up study, the emotional tone of the memories made no difference.
"We have presented clear and novel evidence that systematic forgetting effects can emerge for autobiographical memories by training people to not think about them," the researchers said.
A few further details are worth noting - the participants were surveyed at the end of the studies about whether they'd deliberately withheld details from memories that they'd earlier been asked to suppress, in case they'd feigned forgetting to please the researchers. They said they hadn't, lending further support to the idea that real forgetting had taken place. Moreover, those participants who showed a stronger forgetting effect overall, also tended to be slower at recalling memories that had been suppressed, but which they nonetheless managed to remember in detail later. This is indicative of a partial inhibition of the memories, and lends further support to the central claim of the study.
Important issues for future research to address concern the longevity of the forgetting effect, and the consequences of repeated suppression training. From an applied perspective, Noreen and MacLeod said "an interesting possibility [is that] the kind of forgetting demonstrated in the current study may play a role in bringing about forgiveness and reconciliation through subtle changes in memory that may ultimately lead to changes in associated emotions."
Noreen S, and Macleod MD (2012). It's All in the Detail: Intentional Forgetting of Autobiographical Memories Using the Autobiographical Think/No-Think Task. Journal of experimental psychology. Learning, memory, and cognition PMID: 22686849
Post written by Christian Jarrett for the BPS Research Digest.
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