Far from currently being a conclusive science, research into the nature of human mind continues to accelerate and grow. To the chagrin of all related professional spheres, the field and science of memory could be argued to be in its infancy as well – if the monumental task of creating an encyclopedic understanding and theory of the human mind is the conclusive goal. Due to the interdisciplinary nature of the study of memory, diverse groups of professionals ranging from philosophers, psychologists, biologists, physicians, and technologists all contribute to further the understanding the human mind and its capacity to form memories. The formal scientific study of false memories, memory systems, and how memories are formed or altered at the neurologic level all stand upon firm foundations. Historical and modern theories of memory systems, proof of the existence of false memories, insight from neuropsychological cases, and intricate medical experiments conducted on specific groups of human brain cells each can serve to exemplify some of the progress made.
Humanity itself, collectively and historically, acknowledges that memory can be unreliable. Every natural human language has a way to express the act forgetting, and ways to express the states of being unsure or certain. Between ancient times and the most recent centuries, very little progress was made in understanding human memory. From an ancient perspective, consider the world’s earliest-known written complaint, found on the “Complaint tablet to Ea-nasir,” held by The British Museum. Written in Akkadian cuneiform, the clay tablet documents a dispute regarding the quality of some copper ingots that were sold almost 4,000 years ago. The severe societal consequences of a memory-based oversight in a Bronze Age business disputes could be equated with that of a theft, so it is understandable that the seller was reported to be confrontational and rude when this was brought to his attention, no matter the truth of the matter. From an evolutionary perspective, a lapse of reason or judgment can even prove to be deadly; memory serves biologic imperatives among many other roles.
While the excitement of psychoanalysis in Freud’s Vienna was spreading beyond its borders, the understanding of memory began to accelerate. Although so-called repressed memories were often fictitious, produced through meditative states like hypnosis or erroneously implanted via the psychoanalysts conducting the work, some of those practices are now recognized by modern science as early works within the fields of memory. Psychological, neurological, and physical causes of memory loss were still broadly ill-defined or simply unknown by the late 19th and early 20th centuries. While Freud’s initial followers may have unknowingly perpetuated therapeutic falsehoods, a window into human memory was nonetheless opened and popularized. Paradigm shifts would follow.
Despite undeniably being an inbuilt element of the human condition in ways that the early psychoanalysts had not fully imagined, false memories had to be ‘discovered,’ proven, and validated. After cognitive psychology’s revolution, the number of useful experiments and studies became more frequent, valid, and eventually commonplace.
A famous study by Elizabeth F. Loftus and John C. Palmer, “Reconstruction of automobile destruction: An example of the interaction between language and memory,” can be considered a seminal work. Loftus and Palmer demonstrated how memory can be altered simply by changing the verbs that were used when asking a person to recall what they remembered about a scene. They proved the powerful nature of how the formation of a question can potentially alter memories (Loftus & Palmer, 1974). Loftus and Palmer’s proof of the existence false memories would have many cascading connections ranging from eyewitness testimony, forensic investigations, and offered a glimpse into the function memory itself.
To summarize the study’s experiments: forty-five participants watched various recorded videos of a car accident and were then asked to estimate the cars’ speeds. Between the subjects, the only difference in these questions was the verb used. When the verb had a milder connotation, like ‘hit,’ the participants estimated slower speeds; when the verb was more dramatic, like “smashed,” they estimated higher speeds. Loftus and Palmer considered the results, wondering if they had simply created a biased response with a leading question of sorts, or if they had witnessed the creation of a false memory. Following up on this hunch, their second experiment divided a larger sample evenly into three groups, asking participants to watch videos of car accidents once again. A week later, the groups were surveyed about what they recalled from the videos. One question within the ten-question surveys contained a deliberately altered verb for the two test groups. The group with the more destructive verbs reported seeing shattered automobile glass at the scene of the accidents far more often than group with the milder verbs or the control group. The two latter groups on average both did not remember seeing shattered glass very often, within two percentage points of each other. The ‘surprise reveal’ of the study is that no broken glass was in any of the video clips of the car accidents. False memories had to have been formed if the participants reported seeing any broken glass in the video clips the week prior. The schemas of the participants’ life experiences may have exerted an influence, and the study does not prove how or when some participants formed a false memory, just that some had reported a memory that was false. Nonetheless, evidence of false memories was confirmed.
The elegant design of Loftus and Palmer’s small and controlled study supports the reconstructive memory hypothesis, a hypothesis asserting that each time a memory is recalled, other facets of our knowledge, cognition, and experience, et alia, can blend into that thread of a memory – and potentially forever alter it. The study echoes through time to current recognitions of the nuances of memory. Loftus wrote prolifically, with memory often the subject of her scope. In her article, “Make-Believe Memories,” Loftus summarizes and describes how the misinformation effect can sully eyewitness testimony, noting that “…hundreds of studies have been published documenting memory distortion induced by exposure to misinformation” (Loftus, 2003). The reconstructive memory hypothesis which is responsible for the misinformation effect is just one kind of false memory that has implications far beyond forensic science or litigation.
Endel Tulving, a prominent psychologist during the same era of inquest as Loftus’s earlier works in the 1970’s, asserted the presence of at least two types of long-term memory. Tulving thought that semantic memory of general knowledge and episodic memory of events were encoded serially, in sequence, first to the regions and pathways of semantic memory, then to those of the episodic memory. He also theorized a parallel system of storage, separate yet somehow interdependent, and had found some proof. The interplays between these systems were thought to be able to influence recall as well, though Tulving may not have initially realized how interdependent memory systems truly are, either theoretically or neurologically (Greenberg & Verfaellie, 2010).
Greenberg & Verfaellie offer a thorough, shortform and modern analysis of theories of memory systems (including those of Tulving) from within a journal article about alternative pathways of memory frameworks. Through their work and analysis, they create an alloy of sorts, combining these theoretical memory frameworks in their report called “Interdependence of episodic and semantic memory: Evidence from neuropsychology.” Drawn from and a focusing on neuropsychological cases, they point out how earlier theoretical frameworks of memory can act as useful heuristics to provide perspective for hard science and medicine. Greenberg & Verfaellie observed memories formed in ways that seemed to circumvent earlier frameworks, like aspects of an episodic memory influencing semantic memory and vice versa – not commonly thought to occur in both directions. Their neuropsychological cases may seem like outliers, yet their results suggest that serial encoding is not necessarily the only way in which memories are formed. Their conjecture surrounding alternative or additional memory pathways coexists nicely with existing theories of memory frameworks, the reconstructive memory hypothesis, and the underlying concept of memory reconsolidation, focusing toward the cellular neuroscience of memory.
In a study titled “Reconsolidation of episodic memories: A subtle reminder triggers integration of new information,” support for the idea that memories are not static was given further heft (Hupbach et al., 2007). Though it was previously proven that memories could be altered, this study showed that the reactivation of a memory was a necessary component of the process. That a memory must be reactivated to undergo a reconsolidation implied that the process was active and dynamic; it fortifies the idea that memory reconsolidation has an underlying neurobiological mechanism. Importantly, they further ground their work by noting, “Reconsolidation is an important mechanism for understanding plasticity, potentially explaining how organisms build on prior experience while incorporating new information,” (Hupbach et al., 2007). The mechanism of reconsolidation is most likely a fruit and a side-effect of evolution. If each memory trace is a single filament, these filaments are then a highly malleable material that can be tempered or interwoven, perhaps to learn, to best adapt to better ensure survival.
Most recently, in March 2022, a study focusing on the neuroscience of event segmentation was published, claiming to have discovered some insight on how memories function and form at the level of cellular groups (Zheng et al., 2022). The study focused on groups of cells in patients who were undergoing intracranial recording, the recording acting as a guide for surgeries in the treatment of each patient’s severe case of drug-resistant epilepsy.
Groups of cells were monitored with imaging equipment and specialized software to gather and assess data. The groups of cells monitored were termed “boundary groups” and “event groups.” The cell groups were thought to have different functions despite working together to form memories. “Boundary groups” included cells that responded to either “hard boundaries” or “soft boundaries,” associated with the qualities of a stimulus – like the setting and scene of a photograph. “Event groups” are thought to only respond to hard-boundary stimuli and are not associated with the qualities of a scene or stimulus. “Soft boundaries” include elements that clearly belong together in such a scene, while “hard boundaries” can be thought of as elements that do not belong, something completely different from what might normally be associated or expected, something that indicates a different scene altogether.
An example of some soft-boundary stimuli could include images of an ancient person collecting some copper ingots from a trader of metals. The shelter through which the copper trader conducts business, a balance for weighing goods, people chatting in the background of a market, or uncured clay tablets for record keeping all belong in such a scene. It follows that a hard-boundary stimulus is something outlying and distinct, perhaps a verbal conflict over some unexpectedly poor-quality copper, or better still (for the sake of simplicity), a completely unrelated scene like a waterfall in a forest. A hard-boundary stimulus serves to somehow indicate a different matter. The above examples certainly take artistic liberty, though it may serve to illustrate some of the concepts involved.
Since boundary groups are thought to be involved with the content of such a scene (the relevant or scene-separating stimuli), cells in event groups must also be activated. If the study is correct, when boundary groups and event groups are simultaneously activated with a hard-boundary stimulus, this is when a new memory is formed, a new segment created for the new memory.
Dr. Ueli Rutishauser, one of this intricate study’s authors, added some clarity in a news release: “As you build the memory, it’s like new photos are being added to that event. When a hard boundary occurs, that event is closed and a new one begins. Soft boundaries can be thought of to represent new images created within a single event.” (The NIH BRAIN Initiative, 2022).
Notably, when the study’s patients experienced these hard-boundary events, the monitored groups of event cells activated in frequency ranges that corresponded to those of their respective brain’s overall theta rhythms (Zheng et al., 2022). Theta wave activity is widely associated with memory and learning, a promising correlation paralleled with some of this study’s underlying theory.
Throughout human history, answering questions about the human mind and its capacity to form memories was an impossibility. The advancement of science and technology, coupled with clever and creative thinking, is methodically codifying and answering many of these previously unanswerable questions, thought to beyond humanity’s grasp just a short time ago. Thought the related fields remain young in the grand scheme of human history, the firm footings uncovered by modern sciences will only serve to perpetuate the understanding which it itself seeks.
References
Greenberg, D. L., & Verfaellie, M. (2010). Interdependence of episodic and semantic memory: Evidence from neuropsychology. Journal of the International Neuropsychological Society, 16(5), 748–753. https://doi.org/10.1017/S1355617710000676
Hupbach, A., Gomez, R., Hardt, O., & Nadel, L. (2007). Reconsolidation of episodic memories: a subtle reminder triggers integration of new information. Learning & memory (Cold Spring Harbor, N.Y.), 14(1-2), 47–53. https://doi.org/10.1101/lm.365707
Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13(5), 585–589. https://doi.org/10.1016/S0022-5371(74)80011-3
Loftus, E. F. (2003). Make-believe memories. American Psychologist, 58(11), 867–873. https://doi.org/10.1037/0003-066X.58.11.867
The NIH BRAIN Initiative. (2022, March 7). Researchers Discover How the Human Brain Separates, Stores, and Retrieves Memories. SciTechDaily. https://scitechdaily.com/researchers-discover-how-the-human-brain-separates-stores-and-retrieves-memories/
Zheng, J., Schjetnan, A. G. P., Yebra, M., Gomes, B. A., Mosher, C. P., Kalia, S. K., Valiante, T. A., Mamelak, A. N., Kreiman, G., & Rutishauser, U. (2022). Neurons detect cognitive boundaries to structure episodic memories in humans. Nature Neuroscience, 25(3), 358–368. https://doi.org/10.1038/s41593-022-01020-w
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