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Health Series: Research Spotlight

How resilient are our memories to change?

Study suggests that younger and older adults perform similarly on tests of long-term memory.

by Shamim Quadir (Senior Communications Officer)

We all know that our memories can have the uncanny ability of fooling us into believing they are accurate when they are not.  

Such as when you are sure your favourite player scored a hat-trick ‘that’ year, but which was actually scored three seasons later, or when you distinctly remember you lost your luggage on holiday in Tenerife, when in it was a trip to Lisbon.

Researchers investigating the quirks of human memory have a number of theories to explain how our memories may have been impaired to account for such discrepancies between them and fact.

A study from City, University of London and the University of Hertfordshire, investigated the idea that older memories can get jumbled up with new ones, known as ‘reconsolidation and interference’, and asked whether one’s age has anything to do with the strength of the phenomena.

The study findings suggest that after people are exposed to a potential jumbling of new and old ‘episodic memories’ - our ability to recall specific events and situations we have found ourselves in the past - older adults perform similarly to young adults on accuracy tests of this type of memory. This result was interesting because whilst previous research had been limited, it suggested that older adults perform worse than younger adults.

‘Reconsolidation’ is the concept that our memories can be accessed, adapted in some way, and then stored as the newly adapted version.

This is thought to happen when you recall memories from your past at around the same time you are encoding new experiences to memory. The idea is that the new memories get mixed up with the older memories being recalled, which can lead to an altered recollection of the older events that occurred.

The concept of ‘interference’ in memory research is thought to occur again as old memories are being recalled at a similar time to experiences newly encoded to memory. However, in this scenario,  the old memories interfere with the encoding of those new experiences, committing inaccurate information to memory.

There are two types of explicit memory we can consciously recall:

  • Episodic memory, such as of a wedding day, first day at school, or of a holiday.
  • Semantic memory, which is our recollection of facts, ideas, meaning and concepts – our general knowledge.

Previous research investigating reconsolidation and interference had been confounded by a lack of certainty as to how well experiences had been committed to episodic memory in the first place (the ‘strength’ of the memory) and also the interaction of episodic memory and semantic memory in the brain.

Memories more strongly committed to memory may be more resilient to jumbling,  and semantic memory may help bolster or even skew episodic memory, by filling in gaps in episodic memory.

The current study was designed to ensure only high strength memories were encoded and analysed, account for the impact of semantic memory on understanding whether reconsolidation or interference have an effect on episodic memory, and investigate whether older adult age was a factor in the accuracy of episodic memory.

The study involved two almost identical experiments.

In the first experiment, 178 participants (89 younger adults, mean age 27, and 89 older adults without cognitive impairment and a mean age of 73) were shown eight commonly known images paired with commonly known words, until they could correctly recall all pairings twice in a row (to confirm high memory strength). The next day, half of the image and word pairs were briefly shown again to participants, who were asked to remember them ‘covertly’ (i.e. not reveal that they had remembered), shortly before all images from the day before were shown with new pairings to commonly known words.

A week later participants were asked to recall a range of image and word pairings including the pairings from day one and revised pairings from day two.

The second experiment involved new participants where the images and words paired together were uncommon/nonsense – meaning that a participant’s semantic memory could not be relied on to aid their episodic memory.

The study analysis found that in both experiments, the older adults group took significantly longer than the young adults group to commit the image and word pairings to memory, which was expected.

However, it also found, in both experiments, no effect of reconsolidation or interference, and no difference in the accuracy of episodic memory between older and younger adults either.

These findings are inconsistent with a view that reconsolidation of well learned episodic memories, whether the items memorised are familiar or completely novel, can change or alter the original memory traces.

In fact, whilst not a statistically significant finding, trends in the results are more consistent with the view that for older adults at least, reactivation of older memories may strengthen (not weaken) an original memory trace, and interfere with the learning of new information. Such greater difficulty in learning is consistent with much of the literature on aging and episodic memory.

Commenting on the study, first author, Mark L. Howe, Professor of Psychology at City, University of London said:

These findings are consistent with a growing body of evidence that aging is not associated with a higher rate of memory errors and that older adults’ episodic memories may not be any more susceptible to reconsolidation or interference effects than the memories of younger adults.

The study is published in the journal, Memory.

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