Chapter 8: LTM in Natural Settings: Interactions between Semantic and Episodic Long-Term Memory

Memory plays a crucial role in how we perceive and interpret our experiences. In everyday life, our memories are not isolated entities but intricately intertwined systems that influence each other. This chapter explores the dynamic interaction between episodic and semantic long-term memory (LTM) and examines how these interactions can sometimes lead to memory distortions.

Episodic Long-Term Memory

Episodic memory refers to our ability to recall specific events or episodes from our personal past. When we recount a recent experience or narrate a dream, we draw upon episodic LTM to reconstruct details such as time, place, and emotions involved. However, episodic memories are not always complete or accurate; they are reconstructed using both recalled details and supplemented by our general knowledge of the world.

Semantic Long-Term Memory

In contrast, semantic memory encompasses our general knowledge about the world, including facts, concepts, and language. This type of memory helps us understand and interpret our episodic memories. For instance, when describing an event, if specific details are unclear or forgotten, we fill in gaps using our semantic memory—what we know to be generally true about similar situations.

Interactions and Distortions

The interaction between episodic and semantic LTM can sometimes lead to memory distortions. For example, when recalling a dream, individuals may unintentionally alter details to fit their understanding of how the world works. This process, known as schema-driven reconstruction, involves using schemas (organized knowledge structures, which is just a fancy way of saying semantic memory) to interpret and guide recall of remember information.

Example: Schema Theory in Action

Schema theory posits that we use mental frameworks or schemas to interpret and recall information. These schemas guide our understanding of events and help us fill in missing details based on our general knowledge. For instance, schemas for events like birthday parties or restaurant visits dictate our expectations and interpretations of those experiences.

• Frames and Defaults: Within schemas, specific events are organized into frames, each containing default values based on typical expectations. For instance, in a restaurant schema, the sequence of events (seating, ordering, dining, paying the bill) follows a predictable order unless otherwise specified. In addition, there are typical values that are likely true and if details related to these events are not remembered then people will recall these default values. For instance, if a person typically orders a New England-style IPA at a nice restaurant, this general habit may influence their memory, even if they don’t recall the specific drink ordered on a particular night. Therefore, when recounting a visit to Fishbones Grill in Lewiston, Maine, they might remember having a New England-style IPA, even if they can’t recall the exact drink from that evening.
• Impact on Recall: Research demonstrates that the activation of different schemas can significantly shape how we recall and interpret information. For example, participants were asked to recall a story and were given different titles beforehand: one group was told the story was about landing on an inhabited planet, while the other was told it was about a peace march. These titles activated distinct schemas, leading to differing interpretations and recall biases. The same text was perceived and remembered differently depending on the schema triggered by the title. The text read:

“The view was breathtaking. From the window one could see the crowd below. Everything looked extremely small from such a distance, but the colorful costumes could still be seen. Everyone seemed to be moving in one direction in an orderly fashion, and there seemed to be little children as well as adults. The landing was gentle, and luckily the atmosphere was such that no special suits had to be worn. At first there was a great deal of activity. Later when the speeches started, the crowd quieted down. The man with the television camera took many shots of the setting and the crowd. Everyone was friendly and seemed glad when the music started.”

The differing schemas influenced how participants interpreted ambiguous details, such as whether the "landing" referred to arriving on a planet or gathering for a march. This highlights how schemas can frame and bias memory recall.

Evidence and Critique

While schema theory provides insights into memory reconstruction, it has faced criticism for its oversimplification and ambiguity in defining schemas. Critics argue that the concept of schemas has been overused and lacks clear operational definitions in empirical studies. Furthermore, studies have shown that memory distortions can occur even when individuals do not have a relevant schema, challenging schema theory's explanatory power.

Alternative Explanations

Alternative theories, such as Paivio's dual coding theory, suggest that memory distortions and biases may arise from the interplay between verbal and non-verbal memory systems. According to this theory, memory retrieval is influenced by how information is encoded and stored—whether as verbal descriptions or visual images—which can affect the accuracy and completeness of recall.

Practical Implications

Understanding the interplay between episodic and semantic LTM has practical implications in various fields, including psychology, education, and law. Educators can use insights from memory research to improve teaching methods, while legal professionals must consider memory biases when evaluating eyewitness testimonies.

Bartlett's War of the Ghosts

Bartlett (1932) conducted a classic study using the North Pacific Indian folktale The War of the Ghosts. This study was one of the earliest systematic investigations into human memory for meaningful material. Unlike Ebbinghaus, who focused on nonsense syllables to study memory, Bartlett examined how people remembered culturally unfamiliar narratives and how memory might change over time. Participants read the folktale and were asked to recall it multiple times at varying intervals. Bartlett found that memory was reconstructive rather than reproductive, meaning people combined elements of the original story with their prior knowledge and expectations. This process led to two main discoveries: omissions, where details (e.g., names and specific events) were frequently forgotten, and normalizations, where retellings modified the story to make it more familiar and logical, often downplaying its original strangeness. These results demonstrated that memory is an active process influenced by cultural schemas and personal understanding. The implications of Bartlett’s work are far-reaching, highlighting how our memories are shaped by interpretation rather than mere replication.

Perspective studies

A study by Pichert and Anderson (1977) examined how a participant's expectations might bias the information that is stored in memory. In this research people read a story about two boys exploring a house, with one group instructed to adopt the perspective of a burglar and the other a home buyer. The narrative contained details relevant to both perspectives, such as the house's isolation (important for a burglar) and its renovations (appealing to a home buyer).

For example the person might read:

“The two boys ran until they came to the driveway. “See, I told you today was good for skipping school,” said Mark. “Mom is never home on Thursday,” he added. Tall hedges hid the house from the road so the pair strolled across the finely landscaped yard. “I never knew your place was so big,” said Pete. “Yeah, but it’s nicer now than it used to be since Dad had the new stone siding put on and added the fireplace.”

There were front and back doors and a side door which led to the garage which was empty except for three parked 10-speed bikes. They went to the side door, Mark explained that it was always open in case his younger sisters got home earlier than their mother.

Pete wanted to see the house so Mark started with the living room. It, like the rest of the downstairs, was newly painted. Mark turned on the stereo, the noise of which worried Pete. “Don’t worry, the nearest house is a quarter of a mile away,” Mark shouted. Pete felt more comfortable observing that no houses could be seen in any direction beyond the huge yard.

The dining room, with all the china, silver and cut glass, was no place to play so the boys moved into the kitchen where they made sandwiches. Mark said they wouldn’t go to the basement because it had been damp and musty ever since the new plumbing had been installed….”

Later, participants were asked to recall the story. Those given the burglar perspective remembered more burglary-relevant details, while those with the home buyer perspective recalled more real estate-relevant details. This suggests that the person only stored in memory details that fit their expectations.

However, later research by Anderson and Pichert (1978) showed that when participants were subsequently asked to adopt the opposite perspective, they retrieved new details consistent with this shift. The study highlights how memory recall can be shaped by a person's perspective or mental frame of reference.

Gerald Martin or Adolf Hitler study

Sulin and Dooling (1974) demonstrated how prior knowledge can distort memory through thematic effects. Participants read a paragraph about a character named Gerald Martin or, in another condition, Adolf Hitler, with identical content except for the name. When asked to recognize sentences from the story, participants in the Hitler condition often falsely identified sentences consistent with pre-existing knowledge about Hitler, such as "Hitler was obsessed by the desire to conquer the world," even though these details were not in the text. This distortion effect that was present in the Hitler but not the Martin condition shows that memory was affected by schemas and pre-experimental knowledge. This effect became even more pronounced after a one-week delay. This study highlights how prior knowledge can bias memory recall, especially when the material aligns with existing beliefs or stereotypes.

False Memories

Elizabeth Loftus conducted a groundbreaking study on false memories, often called the "hit/smashed" study. In her study participants watched a video of a car accident and were later asked to estimate the speed of the vehicles. The critical manipulation was the verb used in the question: some participants were asked, "How fast were the cars going when they hit each other?" while others were asked, "How fast were the cars going when they smashed into each other?" Those in the "smashed" condition gave significantly higher speed estimates than those in the "hit" condition. A week later, when asked if they remembered seeing broken glass (which was not present in the video), participants in the "smashed" condition were more likely to incorrectly report that they had seen it. This study illustrated the malleability of memory and how leading questions can distort recall, creating false memories of events that never occurred.

The Deese-Roediger-McDermott (DRM) paradigm is a widely used method to study false memories. In this paradigm, participants hear or read lists of words that are semantically related to a critical word that is not presented (e.g., "bed," "rest," "tired," and "dream" are related to the word "sleep" and the word sleep would not be presented during study). After a delay, participants are asked to recall or recognize words from the list. Consistently, participants falsely remember the critical non-presented word ("sleep") as having been part of the list at a much higher rate than an unrelated word that was also not presented. This finding demonstrates that memory is reconstructive and prone to error, influenced by associations and schemas. The research highlights the role of semantic networks in memory. Specifically, this phenomenon is thought to result from the activation of related concepts in memory, which can spread through a semantic network, strengthening the likelihood of recalling the non-presented word. However, participants' confidence in these false memories is not a reliable indicator of their accuracy, as they may be highly confident that the word was shown, even though it was not. This finding reveals how memory can be influenced by semantic associations and how false memories can occur even with high confidence.

Repressed Memories

Repressed memories refer to the theory that individuals may block out memories of traumatic events to protect themselves from psychological distress, with these memories supposedly being inaccessible to conscious awareness. According to this perspective, these memories may later be recalled with successful therapy. However, this concept cannot be ethically examined in a lab setting because researchers cannot deliberately induce or manipulate trauma in participants. Some therapeutic techniques, like hypnotism or the use of old photos, are believed to potentially trigger repressed memories, but research has shown that these methods can increase the likelihood of creating false memories. For instance, studies have demonstrated that when individuals are prompted to recall memories under hypnosis or shown suggestive photos, they are more likely to "remember" events that never occurred. This has led some to argue that many (or even all) repressed memories may actually be false memories, created through suggestion or therapist influence. The problem with this is that the field of medicine and clinical psychology (and the DSM) recognize dissociative amnesia, which involves an inability to recall important personal information, typically following significant trauma, and suggests that such memory loss can be a natural response to overwhelming stress. While it is possible that a person may lose access to memories due to trauma, it is impossible to definitively determine the truth or falsehood of any memory a person may have in clinical practice. As a result, clinicians must be cautious not to inadvertently implant false memories of events that never occurred, ensuring that therapeutic techniques do not unintentionally alter a patient's recollection of their past.

Anosognosia and Repression

Anosognosia is a condition where individuals are unaware of a significant deficit, such as paralysis, often following a stroke or damage to the right hemisphere of the brain. For example, a person with anosognosia who cannot move their left arm may insist they can, despite clear evidence to the contrary. V.S. Ramachandran proposed that this condition might reflect a form of repression, where the left hemisphere employs a Freudian defense mechanism to maintain the belief that "everything is fine." Normally, the right hemisphere serves as a reality check, providing accurate feedback about discrepancies between beliefs and reality (see Figure 8.1). However, with right-hemisphere damage, the left hemisphere’s tendency to suppress unpleasant truths may dominate, keeping the awareness of the deficit out of consciousness.

Ramachandran's findings suggest that this repression is not absolute. In a striking experiment, he showed that temporarily restoring awareness is possible by irrigating the patient’s left ear canal with cold water. This technique stimulates the vestibular system and temporarily activates the right hemisphere. After this procedure, some patients with anosognosia briefly acknowledge their paralysis, only to revert to denial once the effect wears off. These findings provide fascinating insight into the neural mechanisms of self-awareness and suggest that Freudian defense mechanisms, like repression, may have a neural basis.

Figure 8.1. Depiction of V.S. Ramachandran’s hypothesis regarding Anosognosia. According to this view, Freudian defense mechanisms are located in the left hemisphere of the brain and the right hemisphere provides a reality check. If the right hemisphere is damaged a person may be unable to move the left side of the body but because their brain is not providing a reality check and their Freudian defense mechanisms are left unchallenged they may insist that they are fine.

"Depiction of V.S. Ramachandran’s hypothesis regarding Anosognosia." by Kahan, T.A. is licensed under CC BY-NC-SA 4.0

Process Dissociation Procedure (PDP); Disentangling conscious recognition from unconscious familiarity

Larry Jacoby’s process dissociation procedure (PDP) is a method designed to separate two distinct components of memory: conscious recollection (C) and unconscious familiarity (U). This technique is especially useful for understanding how memory processes may differ, such as in cases of age-related decline. In the PDP, participants are presented with a list of words to study. Then, they are tested on their ability to recognize words from the list under two different conditions: the inclusion condition and the exclusion condition.

In the inclusion condition, participants are asked to fill in a stem completion (e.g., T____) with a word they consciously remember studying (e.g., write table if they remember studying this word) or words they feel familiar with but cannot explicitly recall (e.g., if they can’t remember studying a word that started with t and the word table jumps to mind then write that down). In the exclusion condition, participants are instructed to only write down words that were NOT studied and if the word was consciously remembered to avoid writing that word (e.g., write any word that starts with t other than table - talk, tuba, or tummy - if they remember studying the word table).

Jacoby's formulas for the PDP are designed to quantify (and tease apart) conscious recollection (C) and unconscious familiarity (U) (see Figure 8.2).

Figure 8.2. Depiction of Larry Jacoby’s process dissociation theory. According to this view, memories may be consciously retrievable, may jump to mind because they are unconsciously recalled, or both.

"Depiction of Larry Jacoby’s process dissociation theory." by Kahan, T.A. is licensed under CC BY-NC-SA 4.0

Inclusion = C + U - UC, where:

• C is conscious recollection (memory with specific details),
• U is unconscious familiarity (memory based on a sense of knowing),
• UC is the overlap of both conscious recollection and unconscious familiarity.

Exclusion = U – UC

• This isolates unconscious familiarity by subtracting the overlap with conscious recollection.

By rearranging these equations, Jacoby was able to derive separate measures of conscious recollection (C = Inclusion - Exclusion) and unconscious familiarity (U = Exclusion / 1-C). This distinction is valuable because research has shown that as people age, the conscious component of memory (C) tends to decline more than unconscious familiarity (U).

For example, an older adult might repeatedly ask the same question because the question comes to mind due to unconscious familiarity, but they may not consciously recall having asked it already, leading them to ask again. This is a demonstration of how a decline in conscious recollection can manifest in everyday behavior, helping to explain why older adults may struggle with memory lapses, such as repeating questions without realizing they’ve already asked.

Conclusion

The interaction between semantic and episodic memory is complex and is influenced by culture, belief systems, expectations, and cognitive processes like conscious recollection and unconscious familiarity. Continued research in this area contributes to our understanding of memory dynamics and their implications for everyday life.