Chapter 6 Chapter Summary

Chapter Overview:

Chapter 6 focuses on two interconnected types of explicit memory: episodic and autobiographical. It describes how these types of memories are formed and remembered as well as how the memories themselves can serve as retrieval cues for more generic memories.

Endel Tulving coined the term episodic memory in the 1970s and studied it extensively. More recently, Martin Conway has expanded our understanding of the essential characteristics of episodic memory. Taken together, episodic memory can be described as memories that have a sense of time and perspective—when recalling an episodic memory, you sense that an event occurred in the past and that you witnessed the event firsthand. Episodic memories also evoke the sensations experienced during the original event and are often visual.

One of the most important differences between episodic memory and generic memory is that we experience a sense of remembering an episodic memory whereas we experience a sense of knowing a generic memory. It is this sensation more than the content of the memories that distinguishes the two types of memory.

Not surprisingly, episodic and generic memories are biologically distinct. Episodic memories are formed in the hippocampus; its structure ensures that associations are formed between a variety of experiences. Specifically, the CA3 layer of the hippocampus contains long neurons with thousands of connections. Lisman proposes that when episodes are recorded by the hippocampus, information about the sequence of events and the context of the event are represented. The hippocampus has many neurons with NMDA receptors whose associations strengthen over time thereby providing a temporal code moving from earlier to later events. Context is represented by the pattern of activity of both depolarization and neural firing generated when contextual cues are encoded. Having these two codes allows us to distinguish individual experiences from each other. Similar patterns across multiple events can be encoded into a generic, more fact-based memory. Episodic memories are eventually consolidated to the neocortex.

Retrieving memories is cue-driven, that is, cues probe memory, and if matched, that memory is retrieved. For episodic memory, the cues are contextual. There are two types of contextual cues: environmental cues and internal cues. Environmental cues result in the encoding/retrieval specificity effect whereas internal cues result in the state-dependent effect. The encoding/retrieval specificity effect was introduced in 1973 by Tulving and Thomson who found that retrieval was more accurate when cues present during encoding were also present during retrieval regardless of how good a cue it was. This effect was also demonstrated by Godden and Baddeley in 1975 who found better recall when the location was the same at retrieval as it was during encoding.

State-dependent memory is a similar phenomenon, but the cue that fosters retrieval is the internal state of the person. For example, empirical evidence has shown that if we experience an event while intoxicated on alcohol or other drugs, it is easier to recall it if we are intoxicated than if sober. Likewise, mood and pain can serve as cues for episodic memories.

While the encoding/retrieval specificity effect can offer suggestions to aid in the recall of episodic memories, when students study material over and over, they lay down multiple episodic memories. It is difficult to have cues present during each encoding that will match retrieval. However, students can make the to-be remembered material more personal thereby using the self as an always-present retrieval cue. This is known as the self-reference effect.

Déjà vécu and hyperthymesia are related to episodic memory. Déjà vécu is the sense that you have already experienced a novel situation before. In rare cases, individuals have persistent déjà vécu causing significant disruptions to their lives. While the exact cause of déjà vécu is not known, it seems to be related to activation in the medial temporal lobes. Hyperthymesia is a rare condition where individuals have incredibly detailed episodic memories of their lives (only about 25 people have been identified). Interestingly, people with hyperthymesia have average generic memory.

Classical conditioning is a type of implicit memory and is distinct from episodic memory. However, there is evidence that taste aversion is linked with episodic memory.

Autobiographical memory is more than the store of the episodic memories of our lives; it also consists of the generic memories about who we are.

Martin Conway has proposed that autobiographical memory consists of both an autobiographical knowledge base and a working self. The two components (which exist within a self-memory system or SMS) work together to create a dynamic, changing image of one’s self. The autobiographical knowledge base contains information related to lifetime periods, general events and event-specific knowledge (ESK). Lifetime periods contain memories and knowledge pertaining to specific periods of our lives (e.g., our undergraduate years). General events are representations of repeated specific events in our lives and a series of connected episodes (like a mini history). ESK is of particularly memorable episodic memories. The working self is our representation of our self that both guides and is guided by the autobiographical knowledge base.

Both case studies and brain-imagery research support the idea that episodic autobiographic memories are anatomically distinct from generic autobiographic memories. Basically, while both systems utilize the temporo-parietal and parieto-frontal systems, episodic memories rely more on the right hemisphere whereas generic rely more on the left. 

Flashbulb memories are a specific type of autobiographical memory that result from hearing surprising (usually distressing) news of personal or national significance. These memories appear to be more detailed than normal autobiographical memories. Six criteria are necessary to be classified as a flashbulb memory: the memories must contain information about where they were and what they were doing when they heard the news, who told them the news, how it impacted them, how they felt, and what happened after they heard the news. While originally believed to be exceptionally vivid and accurate, more recent research on flashbulb memories have shown that they are no more accurate than ordinary episodic memories. Conway’s comprehensive model of flashbulb memory suggests that high interest, impact, and emotion result in the vividness typical of flashbulb memories.

Other phenomena related to autobiographical memory are self-concept, the reminiscence bump, nostalgia, and cognitive biases.

Like Conway’s working self, there is empirical support for the notion that our autobiographical memories change as our self-concept changes. This phenomenon even results in a change in perspective so that our memories that are consistent with our current self are viewed in the first person whereas those that are inconsistent are perceived in the third person.

Interestingly, when older adults recall autobiographical events there tends to be a bias with more memories recalled from adolescence and early adulthood. These memories tend to be positive. This finding is called the reminiscence bump. While it appears to be universal, the bump shifts depending on cultural designations of the emergence of adulthood. There are proposed biological, cognitive, and sociocultural explanations for the reminiscence bump; while all have some empirical support, the life-script account seems to be the most robust explanation.

Like the reminiscence bump, nostalgia focuses on positive memories. In fact, it is defined as a “sentimental longing or wistful affection of the past.” Three characteristics typify nostalgia: people recall others who were close to them and/or treasured events, the person recalling the event is in the centre of the memory, and the narrative starts with negative emotions that give way to positive. Interestingly, people are most likely to recall nostalgic events when they are experiencing negative emotions especially loneliness.

While classic studies on mood-congruency and state-dependent memory suggest that negative mood states serve as retrieval cues to evoke negative memories (negative memory bias), the reminiscence bump and nostalgia research suggest a more positive memory bias. That is, when we feel low, we are more likely to recall positive episodic memories. Recent research has found that individuals struggling with depression are more likely to overestimate the number of positive events in their lives.

Other cognitive biases affect our autobiographical memories as well. For example, egocentricity leads us to recall our own behaviours more than other people’s behaviours. Beneffectance, or the self-serving bias, is the tendency to take credit for events that have favourable outcomes and to blame others for events that have unfavourable outcomes. Finally, conservatism (also known as confirmation bias) suggests that we tend to recall autographical memories that support our world view.

Learning Objectives:

Having read this chapter, you will be able to do the following:

1. Describe the characteristics of episodic memory.
2. Differentiate between knowing and remembering.
3. Explain how episodic memories are formed.
4. Explain how state-dependent memory is connected to episodic memory.
5. Differentiate between episodic memory and autobiographical memory.
6. Discuss phenomena associated with autobiographical memory, including the reminiscence bump and nostalgia.
7. Describe how cognitive bias can influence autobiographical memory.
8. Define a flashbulb memory.
9. Discuss unique attributes of flashbulb memories as well as attributes that are common to other episodic memories.
10. Discuss the neuroscience of autobiographical memory.