Introduction to episodic and semantic memory

Long-term memory (LTM) refers to the storage of information over extended periods, potentially lasting a lifetime. The multi-store model of memory describes LTM as a single store, but more detailed theories expand on this. Episodic and semantic memory provide a deeper explanation of LTM, focusing on different types of knowledge we hold.

These types of memory are both forms of declarative memory, which involves consciously recalling facts and events – essentially 'knowing that' something is the case. For example, knowing the capital of France or remembering a recent personal event both fall under declarative memory.

The distinction between episodic and semantic memory was proposed by Tulving in 1972. This theory builds on the multi-store model by elaborating on how LTM stores personal experiences versus general knowledge.

Episodic memory

Episodic memory stores personal experiences and events from our lives, making it autobiographical in nature. This type of memory allows us to recall specific episodes, including the context in which they occurred.

Key features of episodic memory

• Autobiographical events - It includes memories of times, places, people, and associated emotions, such as remembering catching the bus to college this morning.
• Context-dependent - Retrieval is improved when the original learning context is recreated, as the memory is tied to specific circumstances.
• Susceptible to change - During recall, episodic memories can be altered or transformed, meaning they are not fixed recordings but can evolve over time.

Semantic memory

Semantic memory stores general knowledge and facts that are not tied to personal experiences. This allows us to understand concepts and meanings without recalling when or where we learned them.

Key features of semantic memory

• General knowledge - It includes facts, concepts, and vocabulary, such as knowing that Paris is the capital of France.
• Derived from experiences - Semantic memories often originate from episodic memories but become detached from their personal context over time.
• Stable and generalised - Unlike episodic memory, semantic memory is less prone to transformation and stands alone as abstract knowledge.

Relationship between episodic and semantic memory

Episodic and semantic memories are interconnected, with semantic memory often building upon episodic experiences. This relationship explains how personal events can contribute to broader knowledge.

How episodic memory supports semantic memory

• New facts and concepts are initially learned through personal episodes, which form episodic memories.
• Over time, these episodic memories can transition into semantic memories by losing their sensitivity to specific events.
• This gradual shift generalises the information, making it standalone knowledge without the original personal context.

For example, repeatedly experiencing rainy weather in a particular city might start as episodic memories of specific days, but eventually become a semantic memory that 'it often rains there'. This process shows how LTM is dynamic, with episodic memory underpinning and evolving into semantic memory.

Reconstructive memory

Reconstructive memory is a theory proposed by Bartlett that views memory not as a perfect recording, but as an active process of rebuilding past events. This reconstruction is influenced by our existing knowledge and attitudes during encoding, storage, and retrieval.

Key principles of reconstructive memory

• Imaginative reconstruction - When recalling an event, we piece together details, which can change based on how we process the information.
• Influence of attitudes - Our responses and views at the time of an event can alter how we remember it later.
• Not a blank tape - Memory is flexible and can be modified, leading to potential inaccuracies.

This theory highlights that recall is an active process, shaped by individual factors rather than a passive replay.

Role of schemas in reconstructive memory

Schemas are mental frameworks or 'units' of knowledge that organise information about frequently encountered people, objects, or situations. They help us interpret and remember information but can also introduce errors.

How schemas influence memory

• Aiding encoding and retrieval - Schemas provide a structure for processing new information, making it easier to store and recall. For instance, a 'beach schema' might include sand, sea, and umbrellas.
• Causing distortions - If information does not fit an existing schema, it may be altered to match. This can lead to errors, such as recalling a beach umbrella in a scene where none was present, because it fits the schema.
• Fitting unfamiliar information - Schemas can distort details that are unfamiliar or unacceptable, forcing them to align with what we already know.

While schemas improve efficiency in memory processing, they can reduce accuracy by filling in gaps with assumed details.

Individual differences in memory processing

Cognitive psychology examines how people process information, revealing that individuals vary in how they encode, store, and retrieve memories. These differences arise from personal experiences and brain structure.

Factors contributing to individual differences

• Schemas and experiences - Everyone develops unique schemas based on their life events. For example, one person's schema of police might view them as protectors, leading to positive memories, while another's might see them as suspicious, resulting in negative recollections.
• Episodic memory uniqueness - Since episodic memories are personal episodes, they naturally differ between individuals, as highlighted by Tulving.

These individual differences mean that two people can experience the same event but remember it differently.

Impact of brain damage on memory

Brain damage, particularly to areas like the hippocampus, can disrupt memory functions, but its effects vary between individuals due to the unique nature of each case.

Classic examples illustrate the role of the hippocampus in memory.

HM case study

• Participants - HM, a patient who underwent surgery to remove parts of his temporal lobes, including the hippocampus, to treat severe epilepsy.
• Procedure - After the surgery in 1953, HM could no longer form new long-term memories.
• Results - He retained old memories and short-term memory but suffered anterograde amnesia, unable to create new episodic or semantic memories.
• Conclusions - This demonstrated the hippocampus's crucial role in transferring information from short-term to long-term memory.
• Limitations - As a single case, findings may not generalise, and ethical concerns arise from the irreversible damage.

Clive Wearing case study

• Participants - Clive Wearing, a musician who contracted a herpes simplex virus in 1985, damaging his hippocampus.
• Procedure - The virus caused encephalitis, leading to severe memory loss.
• Results - Wearing has profound amnesia, with a short-term memory span of seconds and inability to form new memories, though he retains some procedural skills like playing the piano.
• Conclusions - This supports the importance of the hippocampus for episodic memory, while showing that semantic and procedural memories can be partially preserved.
• Limitations - Individual factors, such as the specific virus and brain areas affected, make it unique and hard to replicate.

These cases show consistent effects on memory from hippocampal damage, but individual differences in damage extent and personal background lead to varied outcomes.