According to the dualistic interpretation of mind, the self uses the brain, but the brain is distinct from the self. Evidence from a new study shows that memory circuits assist the mind in recalling thoughts by associating them with sensations. The mind can use the brain’s storage mechanisms to sort more important or urgent memories for faster recall.
In Scientific Reports, David Stawarczyk and Arnaud D’Argembeau present the question they wanted to investigate:
Daily life situations often require people to remember internal mentation [i.e., mental activity], such as their future plans or interpretations of events. Little is known, however, about the principles that govern memory for thoughts experienced during real-world events. In particular, it remains unknown whether factors that structure the retrieval of external stimuli also apply to thought recall, and whether some thought features affect their accessibility in memory. [Emphasis added.]
What Were They Thinking?
The scientists thought about this, and came up with a way to test it using modern technology on college students.
To examine these questions, we asked participants to undertake a walk on a university campus while wearing a lifelogging camera. They then received unexpected recall tasks about the thoughts they experienced during the walk, rated the phenomenological features of retrieved thoughts, and indicated the moment when they were experienced.
While looking inside another person’s “self” is not possible, the researchers could ask the participants to describe what they were thinking about in space and time. Notably, the experiences that involved conscious choices were more easily recalled.
Results showed that thought retrieval demonstrates primacy, recency, and temporal contiguity effects, and is also influenced by event boundaries. In addition, thoughts that involved planning and that were recurrent during the walk were more accessible in memory. Together, these results shed new light on the principles that govern memory for internal mentation and suggest that at least partially similar processes structure the retrieval of thoughts and stimuli from the external environment.
These observations appear to support the view that the conscious self uses memory as a tool. The mind uses the brain; it is not a passive illusion conjured up by the brain. The brain is active and ready, storing each sensation as we walk through daily life, but thoughts that involve planning are more readily recalled. It’s as if the self tells the brain, “Remember this,” and the brain obliges like a computer operator or librarian, pigeonholing the data where it can be recalled more easily later.
Choosing to Remember
Everyone has had the experience of intuition at the wrong time. You’re busy with something else, when an idea flashes into your mind, perhaps a melody for a song you want to write, a project you want to start, or something you want to say to counsel a friend or family member. The authors use the example of a scientist thinking of a novel experiment for research while driving home. It’s impossible to stop and write it down at the moment, but you want to remember it later.
Research on the stream of thought in daily life has shown that the mean duration of a thought segment is about 14 seconds, suggesting that people may experience between 4,000 and 5,000 thoughts during a 16-hour day.
Many of these thoughts are likely forgotten, the authors say, probably because there is only so much a person can focus on in the sea of perceptions and stimuli going on around us. If the intuition is valuable enough to the self, the brain will assist future recall of the intuition, but is not causing it; the “user” or self asks the brain to store that thought in its physical hardware.
To help the user recall what it has selected as important, the brain forms an association between the intuition and the external stimuli occurring at that moment. It might be a mental picture of what street you were driving on, what book you were reading, or what child was up at bat on the ball field when the thought occurred.
Peering into the Thought Life
The authors recount earlier experiments to probe the thoughts of others. Some researchers asked people to wear beepers that would go off at random times. The subjects were asked to write down what they were thinking at the moment, and to rate the thoughts. In 1988, W. F. Brewer “found that thoughts that received higher recall scores were rated as more emotionally pleasant, personally significant, and exciting during the experience sampling phase.” Other research probed the recall of real versus imaginary events. In such cases, it was found that “perceptual characteristics of memories decreased more over time for imagined than perceived events,” even though imagined events might have been more intense and were recalled more often at the time (think of replaying in your head an intense scene in a movie). Other research investigated the recall for “future-oriented thoughts” such as planning a camping trip, envisioning what needed to be done. The authors find these past research efforts inadequate to address their question.
While these studies provide clues about the factors that influence memory for thoughts, little is known about the processes structuring the retrieval of internal mentation. Most notably, it remains unknown whether principles that govern the recall of stimuli from the external environment also apply to memory for thoughts.
To continue, some terms need to be defined:
- Primacy: The first item in a list has primacy.
- Recency: The last item in a list has recency.
- Temporal contiguity: The tendency to recall items in a list in the same order they were presented.
Prior research had shown that people asked to recall a list they memorized tended to reiterate them according to these traits. But what about people’s ability to recall their own internal thoughts?
An important difference between the stream of thought and lists of items in memory experiments is that thoughts tend to be organized in coherent sequences, whereas items in laboratory experiments are typically presented in random order… In daily activities, thoughts may follow, at least in part, the structure of ongoing events. There is extensive evidence that people automatically segment everyday activities into events and sub-events according to changes in actions, contexts, and goals.
A transition between events, called an event boundary, such as getting out of the car and walking into the house, provides an anchor point for recall of thoughts. Our thoughts are organized within these real-world segments between event boundaries.
Whistle While You Work
In order to explore recall in more depth, Stawarczyk and D’Argembeau combined two methods in their experiments. Participants were given “surprise free recall tasks” during which they had to state what they had been thinking during their walks. These were cross-checked against the pictures taken by the camera. The participants looked at the images to associate when they had certain thoughts. Could certain features predict how accessible certain thoughts were in the memory over others?
Considering that an adaptive function of episodic memory is to provide information that can be used to support future decisions and behavior, we expected that the future orientation and planning function of thoughts would predict their accessibility in memory. Furthermore, we predicted that features that are well-known to influence memory for external stimuli, such as self-relevance, distinctiveness, emotional valence, and rehearsal would also predict the accessibility of thoughts in memory. Finally, recent studies on mind-wandering have shown that stimulus-dependence and task-relatedness are important dimensions of thoughts, with people spending from 30% to 50% of their daily life engaged in mind-wandering episodes that are unrelated to their ongoing activity and decoupled from current sensory input. At a more exploratory level, we investigated whether these two dimensions predict the accessibility of thoughts in memory.
Thoughts of Evolution
The word “adaptive” in that first sentence may trigger thoughts of evolution, but actually, many of the other words indicate intelligent design: information, decisions, future orientation, planning. This is what intelligent minds engage in. They are opposite to the predictable outcomes of natural laws. Gravity says an arm left to itself will fall. A mind says, “I choose to raise my arm.” A mind plans, decides, and looks ahead to potential realities that may be entirely unique and creative. Even while daydreaming, creative minds can be thinking of things “unrelated to their ongoing activity and decoupled from current sensory input.” A cheerful factory worker can be whistling as he works, thinking of the show it came from, or even adding his own lyrics to it, till interrupted by an event boundary — the quitting-time bell.
All the brain does is assist recall of such creative mental activities. The worker might recall the lyrics he was imagining by associating it with hearing the bell. The researcher might recall the novel experiment she was thinking of by associating it with getting on the turnpike. External cues and event segments help organize our thoughts. The mind uses the brain; the brain is not the mind.
The human memory system associates each new experience within a spatiotemporal context. There is evidence that this context is reinstated when the experience is recalled, and serves as a cue to guide the retrieval of other associated experiences. The role of context in memory recall accounts for temporal contiguity effects and may also explain primacy and recency effects, considering that the beginning and end of a list are contextually more distinct than the middle of the list, which facilitates the retrieval of associated items. The present results suggest that this context model of memory search may also account for the structure of thought recall.
Like Captain Kirk on Star Trek asking, “Computer: give me yesterday’s travel log,” the brain facilitates retrieval of the thoughts the mind chooses to recall. Remember this: memory requires ID, because Stawarczyk and D’Argembeau are about to end with an imaginary Darwinian just-so story:
These results are concordant with the proposal that an important function of episodic memory is to store information that is useful to guide decisions and future behavior. They also fit well with the idea that the greater accessibility of planning thoughts in memory results from an evolutionary process whereby mental contents that enhance survival chances are better remembered.
That’s their only reference to evolution in the whole paper. Certainly memory is valuable for survival (and other things), but that cannot be the explanation for its origin. Otherwise, we would have to conclude that these authors were not searching for truth. They were only trying to survive. They themselves realize that there is more going on in the creative, intelligent mental self than that:
Finally, it is also worth noting that planning thoughts might entail a range of cognitive processes that could increase their accessibility in memory. For instance, several studies that examined the features of planning vs. non-planning thoughts found that the former are more elaborate, require more cognitive effort, and are more tightly linked with the self and personal goals.