Remembering Accidentally on Purpose

Involuntary memory may compensate for a decline in voluntary memory as we age.

Posted Aug 08, 2017

"Brain, Turn On, Education, Read" by Geralt / Pixabay / CC0 Public Domain
Source: "Brain, Turn On, Education, Read" by Geralt / Pixabay / CC0 Public Domain

It is a well-known and unfortunate fact of life that our ability to remember declines as we get older.  If we live long enough, virtually all of us will catch ourselves saying at some time or other that our memory “isn’t what it used to be.”  When such inevitable moments arise, however, to summarily malign our memory as “bad” is neither an accurate nor a particularly meaningful description of the new deck of cards we are gradually dealt as we grow older.

Human memory is not a single faculty but a number of different storage and retrieval processes, and not all of them decline as we age.  Our semantic memory, for example—our knowledge of facts, concepts, and ideas—does not diminish as we grow older, but in fact increases as we accumulate more information along the journey of our lives.  When we complain about age-related declines in our ability to remember, it is typically our episodic memory—memory of events we have experienced—that we are talking about.  When we park our car in the grocery store parking lot, and come out a few minutes later completely clueless about where to find it, our episodic memory has failed us.  We have no trouble with related semantic memories—the name of the store, the street on which it is located, and so on, but we cannot for the life of us remember the experience of parking our car in a specific space in the lot before we went inside.

As unpleasant as the idea of a future with an almost certain decline of episodic memory in it may seem to us, the prospects for our future episodic memory are not uniformly bad.  Recent studies have indicated that, while our voluntary episodic memory declines with aging, no such decline occurs in our involuntary episodic memory.  In other words, our memories are still there; we just have more difficulty retrieving them at will.

In a recent pair of studies in Denmark, participants were shown a film of common, everyday experience recorded from a first person perspective.  Later, they were shown another first person perspective film that was different from the first, but shared the same context of the first film, as well as many of its features.  As a measure of their voluntary memories, participants were asked to record as many details from the first film as they could remember.  As a measure of their involuntary memories, the participants were asked to record the approximate number of memories of the first film that spontaneously came into their minds while watching the second one.

In the voluntary memory phase of the study, older participants (between 65 and 89 years of age), recorded approximately the same number of details as the younger participants (between 17 and 25 years of age), but it took the older participants significantly longer to recall these details.  This result indicates that the availability of memory details was the same in both groups, but accessibility to these details was reduced in the older group. In the involuntary portion of the study, there was no difference between the two groups in the number of involuntary memories from the first film they reported after watching the second.   

A second related study, designed to measure voluntary and involuntary memory frequency in a “real life context,” required two groups of participants to record the number of either voluntary or involuntary memories (depending upon which group they were in) that came into their minds during a normal day.  As in the first study, younger and older participants recorded approximately the same number of involuntary memories.  Regarding voluntary memories, however, where in the first study older participants recorded the same number of memory details as the younger participants but merely took longer to retrieve them, in the second study the older participants reported a significantly lower number of voluntary memories.  Both studies support the hypothesis that, while voluntary episodic memory declines with aging, involuntary episodic memory remains stable into older adulthood, and in fact becomes “a more dominant way of accessing past events” as we age.

As a possible cause for this increased reliance upon involuntary memory in older adults, the researchers who conducted the studies cite the interaction of two factors: an age-related decline in executive processes that makes voluntary strategic remembering more difficult, and a greater tendency in older adults to “process peripheral and task unrelated information.”  The idea that, in addition to finding it more difficult to voluntarily access autobiographical memories than we once did, we are also more easily distracted by peripheral stimuli, may seem disheartening to us at first glance.  We might even picture ourselves drifting through our later years like the famously forgetful blue tang fish Dory (of Finding Nemo and Finding Dory), who suffers from a similar combination of memory loss and distractibility.

According to the researchers, however, this increasing tendency to be distracted by peripheral information as we age may provide an unexpected benefit—a silver lining, as it were—by increasing our exposure to potential memory cues.  Heightened sensitivity to memory triggers may represent “an adaptive compensation for age-related difficulties with strategic retrieval of past events,” allowing us involuntary access to those memories that we have a hard time retrieving voluntarily.  This hypothesized adaptive function is, in fact, not unlike an involuntary memory experience in Finding Dory that helps to reunite Dory with her parents.  While looking at a map of the Marine Life Institute, where she believes her parents live, her eyes are drawn to the image of a purple shell.  Distracted from her task of searching the map, she gleefully announces, “Hey look, shells,” but the picture that has distracted her triggers an involuntary memory of her parents that ultimately helps to lead her back to her them.

The fact that Dory’s seemingly random involuntary memory is vitally relevant to her current situation illustrates another important characteristic of involuntary memory as an adaptive compensation for declining voluntary memory.  Involuntary episodic memories are frequently “activated in response to cues that provide a unique feature overlap to a past event,” increasing the probability that the remembered event “will bear some functional relevance to the retrieval situation.”  Of all the cues in Dory’s environment, it was the image of the purple shell that drew her attention, and the involuntary memory that it triggered—her mother’s preference for purple shells—turned out to be exactly what she needed to carry out her goal of finding her parents.

The decline in voluntary episodic memory that comes with aging is undeniably inconvenient.  Life is too short to spend precious moments searching the grocery store parking lot for our car.  But if the hypothesis advanced by the researchers who conducted this pair of studies is valid, our brains may very well have provided us with a means of compensating, to a degree at least, for that decline.  We may view the tendency of our attention to be lured away from an important task by the various purple shells in our environment as a nuisance, but if the important task in which we happen to be engaged involves trying to remember something, we might just find what we’re looking for by following our attention wherever it leads us.