Why Random Memories Flash Into Our Heads

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During my 20-minute commute to work this morning, I passed a house with a purple glass gazing ball in the front yard and was suddenly transported back to the tiny public library in the town I lived in when I was a little boy. In my mind’s eye, I was sitting at a table near the circulation desk flipping through a large Tom and Jerry picture book—a favorite of my five-year-old self—while the kindly librarian snacked on saltine crackers, wrapping her lips around them before biting in order to maintain a library-appropriate hush.

I puzzled over the inexplicable memory flash until I “saw” the page to which I was turned, where a mischievous Jerry hurls a large juicy plum at Tom’s face. The plum in the picture was exactly the same distinctive shade of purple as the gazing ball, the sight of which had spontaneously triggered the memory.

As unexpected as that particular memory was at that particular moment, the experience of flashing on some random episode from the past during my daily commute was by no means unprecedented. I frequently experience such spontaneous memories while I’m on the road, finding them to be a source of passing interest and occasionally even enjoyment (depending on their content, of course), but thoughts about the work day ahead usually edge them out of my attention before I’ve given them any serious thought. A psychologist in the UK gave his commute-associated memories some serious thought, however, and even made them the subject of a study recently published in the journal Memory.

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Involuntary Autobiographical Memories on the Morning Commute

Reflecting on the substantial body of research on “spontaneous cognitions” that has been conducted in recent decades, Andrew Laughland from the University of Hertfordshire, Hatfield, saw his daily commute to and from work as a possible source of data to fill in “several gaps” in the research on involuntary autobiographical memories (IAMs).

The most common source of prior research on IAMs has been the use of diaries, where participants manually recorded IAMs as they occurred, and Laughland noted that the rates reported in these studies seemed to be lower than those he personally experienced while driving. Reasonably assuming his experience to be fairly typical of the average person’s, he hypothesized that the discrepancy was a result of the methods used to gather data in previous studies.

To test this hunch, Laughland designed an experiment in which his own car driving could be used as a “naturalistic activity” during which IAMs could be monitored via audio recording. Wearing a tie-clip microphone connected to a digital recorder, he recorded his entire 37-minute journey from the time he pulled out of his driveway—recording a sentence or two about what had happened immediately prior to leaving—to the moment he pulled into a parking space at the university.

This continuous audio recording format was designed to capture “free-flowing thoughts” that would otherwise likely be forgotten by the journey’s end. His experiment lasted a year and a half and included a total of twenty commutes.

The Frequency of IAMS in Everyday Life

At the conclusion of the experiment, Laughland discovered that he had, indeed, recorded more IAMs than had previously been reported.

Earlier studies in which participants used diaries to record IAMs reported rates of about two to five per day. Other studies using clickers to record the occurrence of IAMs without describing their content reported rates of between 22 per day and 10 per hour. Laughland’s audio recordings of his daily commutes, on the other hand, produced IAMs at a rate of nearly one per minute, supporting his hypothesis that IAMs occur far more frequently in real life than formal research has suggested.

"Dynamic" vs. "Static" Cues of IAMs

In addition to allowing Laughland to record IAMs at a greater frequency than in previous studies, the continuous audio recording method also allowed him to record them in far greater detail, providing some “novel and important” insights into the way involuntary autobiographical memories are triggered.

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The first of these insights involved the types of cues that trigger involuntary memories. Laughland’s recorded observations about what was going on around him as the memories popped into his head revealed that “dynamic” rather than “static” environmental cues are more likely to trigger IAMs.

In other words, new or unexpected details encountered on his trips (e.g. varying weather conditions, or songs on the radio) were far more likely to trigger memories than those details that were always present (e.g. buildings or road signs). This finding highlights the somewhat ironic role that novelty plays in triggering autobiographical memories in our daily lives, with new details in our environment eliciting old memories from our past.

Memory "Chains"

Another interesting finding of the study involved memory “chaining,” in which memories are triggered by a preceding memory rather than by some other internal or external cue. Such memories can often be perceived as new occurrences, but Laughland’s retrospective examination of his audio recordings revealed that many of the IAMs that he perceived to be independent had actually been cued by a prior memory (or memories).

In fact, as many as 23 percent of the IAMs he recorded were chained memories, suggesting that memory chaining is more common than has previously been reported.

IAM "Priming"

Yet another insight provided by the study has to do with the “priming” of IAMs. Very often, an autobiographical memory will unexpectedly pop into our heads, seemingly out of nowhere. Laughland’s review of his audio recordings, however, revealed that many of the spontaneous memories that he recorded during his commutes were not, in fact, spontaneous at all, but had been triggered by cues that he had encountered several seconds or even minutes earlier.

At the moment, the time gap between the cue and the memory it triggered initially prevented him from perceiving a connection between the two events. But the recording revealed that the environmental stimulus had actually “primed” a memory or memories that he recalled later, seemingly out of the blue.

Laughland’s study, and the novel method he employed to gather data, provides evidence that involuntary autobiographical memories are a far more regular occurrence in our daily lives than previous research has suggested. It also gives new insight into how these memories actually occur, indicating that far fewer of them are truly spontaneous than appear to be, getting triggered by cues in our environment rather than simply popping into our heads out of nowhere.

One general point that the study makes clear is what a good opportunity our daily commute offers for experiencing involuntary autobiographical memories. Research on IAMs and related phenomena has shown that “spontaneous thoughts and memories occur more often when people are engaged in undemanding, habitual activities” such as driving.

In other words, when not focused on some task that requires focused attention, our minds tend to wander—and as this study shows, it is very often our autobiographical pasts to which they wander. And if we pay attention to these mind-meanderings during our morning commute, instead of tuning to NPR or cueing up a podcast, we never know where they may take us.

Indeed, given the right environmental cue, they might just lead us back to a cozy little library from our childhood—a brief mental vacation in our distant past to prepare for the busy day in our immediate future.

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