Declarative memory, also known as explicit memory, is a type of long-term memory that involves conscious recall. It’s divided into two categories: semantic memory for facts and general knowledge, and episodic memory for personal experiences and specific events.
Key Takeaways
- LTM: Long-term memory isn’t a single store. It splits into declarative (explicit) and non-declarative (implicit) memory. Implicit memory includes procedural memory (skills like riding a bike) and conditioned responses.
- Declarative Memory: Stores facts and events we’ve personally experienced. Recalling it takes conscious effort, since the information must be brought to mind and “declared.”
- Episodic & Semantic: Episodic memory and semantic memory are the two components of declarative memory.
- Semantic vs Episodic: Semantic memory covers general knowledge, facts, and ideas. Episodic memory covers personal experiences, like birthdays.
- Development: Throughout our lifetime, there is a gradual transition from episodic to semantic memories.
Declarative memory is part of long-term memory involving “knowing that”, for example, London is the capital of England, zebras are animals, and the date of your mum’s birthday (Cohen and Squire, 1980).
Declarative memory is also known as explicit memory, as it consists of information that is explicitly stored and involves conscious effort to be retrieved. This means that you are consciously aware when you are storing and recalling information.
Types of Declarative Memory
Episodic memory, together with semantic memory, is part of the division of memory known as explicit or declarative memory.
While episodic memory involves a person’s autobiographical experiences and associated events, semantic memory involves facts, concepts, and skills acquired over time.
Declarative memory depends on the hippocampus and surrounding medial temporal lobe. It’s typically fast, often forming in a single trial. It’s also flexible, useful for reasoning about new situations. Damage to this brain region causes the classic amnesic syndrome: new facts and events can no longer be stored.
Episodic Memory
Episodic memory is part of long-term declarative memory and comprises a person’s unique recollection of experiences, events, and situations.
The Canadian psychologist Endel Tulving first introduced the term ‘episodic memory’ in 1972 to distinguish ‘remembering’ from ‘knowing.’
Tulving later described this as autonoetic (self-knowing) consciousness (Tulving, 1985). It feels like mental time travel. You mentally relive a past moment from your own point of view, rather than simply knowing it happened.
Specific events, general events, personal facts, and flashbulb memories constitute different types of episodic memory.
They are a person’s unique memory of a specific event. That means your recollection will differ from someone else’s account of the very same experience, such as your first day of school.
Episodic memory has 3 elements: specific details of the event (time and place), context (what happened next), and emotions (how you felt).
Examples of episodic memory include recalling your first trip abroad, or remembering exactly where you were when Donald Trump won the 2016 election. Even your first day of college counts.
Types of Episodic Memory:
- Specific events involve the recollection of particular moments from an individual’s autobiographical history. Recalling the first time you dove into the ocean is an example.
- General events involve recalling the feelings associated with a certain type of experience. Recalling what it is like to dive into the ocean, in general, is an example of this type of episodic memory. You may not remember each occasion wherein you dove into the ocean. But you do have a general recollection of having dived many times into the ocean—upon which your feeling is based.
- Information intricately tied to a person’s experiences constitute personal facts. Knowing the color of your first bicycle and the name of your first dog are some examples.
- Flashbulb memories are exceptionally vivid and highly detailed ‘snapshots’ of moments or circumstances wherein you learned important or surprising pieces of news (Brown & Kulik, 1977). Recalling the moment you heard about the death of a family member or a major tragedy such as the 9/11 attacks might be an example.
- It should be noted that there is much debate as to whether the vividness of a flashbulb memory stems from a virtual flash produced by the emotional intensity of a specific experience, or from a propensity to rehearse consequential moments—which can immensely strengthen the memory.
Neural Networks
Episodic memories can be stored in auto-associative neural networks. This requires that the representation of each stored memory include information about the spatiotemporal context in which it was formed (Khalil, Moftah & Moustafa, 2017).
Neural networks are built from interconnected neurons. Together, they produce different intra-brain cognitions and shape how the body transmits and receives messages (Henderson, 2012).
Additionally, these networks can contract or expand based on the type of information being processed at a given time (Nestor, Kubicki, Gurrera, Niznikiewicz, Frumin, McCarley & Shenton, 2004).
Semantic Memory
Semantic memory is a type of long-term declarative memory. It stores facts about the world, independent of any particular event or context. This is “knowing that” something is true, such as that Paris is the capital of France.
Tulving (1972) called it a “mental thesaurus.” It’s our organized store of words, concepts, and meanings. Recalling a fact from it feels like knowing, not re-living a moment, unlike episodic memory’s autonoetic consciousness. It relies mainly on the anterior temporal lobes.
The Canadian psychologist Endel Tulving first introduced the term ‘semantic memory’ in 1972 to distinguish ‘remembering’ from ‘knowing.’
Semantic memory concerns knowledge about the world that is shared by everyone, not personal knowledge. This includes the function of objects and what behaviour is appropriate. It even covers abstract concepts, such as maths.
Some examples of semantic memory:
- Recalling that Washington, D.C., is the U.S. capital and Washington is a state.
- Recalling that April 1564 is the date on which Shakespeare was born.
- Recalling the type of food people in ancient Egypt used to eat.
- Knowing that elephants and giraffes are both mammals.
Episodic and Semantic Memory
Together, episodic and semantic memory make up declarative memory.
Episodic memory involves recollections tied to a specific time and place. It lets you mentally travel back and re-experience the emotions attached to them.
Semantic memory works differently. It’s built from skills, facts, and concepts acquired over time, largely through the accumulation of episodic memories.
For instance, each visit to Paris is an episodic memory, but the general impression of what Paris looks like becomes its semantic representation.
Tulving originally proposed that episodic and semantic memory compete against each other during retrieval.
Later research complicated this picture. Experiments using Latent Semantic Analysis (LSA) found that stronger semantic cues actually go with stronger episodic retrieval, not weaker (Howard & Kahana, 2002).
More recent work goes further, treating the two systems as interdependent rather than competing.
Their interaction is now seen as an essential part of normal declarative memory, not a flaw in the model (Renoult & Rugg, 2020).
The two systems are also linked biologically. Damage to the medial temporal lobe can impair both episodic and semantic memory.
This happens, for instance, in anterograde amnesia, the inability to form new long-term memories after brain injury (Tulving & Markowitsch, 1998).
Critical Evaluation of Declarative Memory
Psychologists are confident that declarative and non-declarative memory are separate systems because of dissociations: patients who lose one kind of memory while keeping the other intact.
A single dissociation is only suggestive, since one task might simply be easier than another. A double dissociation is the decisive evidence: one patient loses ability A but keeps B, while a different patient loses B but keeps A.
Key Study: H.M. and the Case for Separate Memory Systems
The founding evidence comes from the patient Henry Molaison (H.M.) (Scoville & Milner, 1957; Milner, Corkin, & Teuber, 1968).
- Aim: To test whether all long-term memory depends on the medial temporal lobe, or whether some learning survives without it.
- Method: In 1953, surgeons removed large parts of H.M.’s hippocampus (plus nearby structures) to treat severe epilepsy. Years of testing then compared his memory for new facts and events against his ability to learn a new physical skill, mirror-drawing.
- Results: H.M. could no longer form new memories of facts or events, and couldn’t recognize people he’d met minutes earlier. Yet his mirror-drawing improved steadily across sessions, even though he had no memory of ever practicing it before.
- Conclusion: Long-term memory is not one single system. The hippocampus is essential for new declarative memories, facts and events, but not for procedural, skill-based learning, which other brain systems support.
Contemporary Research
The modern consensus comes from Squire and Dede’s (2015) synthesis, an integrative review pulling together decades of patient studies, brain imaging, and animal-lesion research. It asked how many memory systems exist. It also asked how each one maps onto the brain.
The review concluded that declarative memory, semantic and episodic, depends on the hippocampus and medial temporal lobe. Non-declarative memory, by contrast, is a family of separate systems: skills and habits (striatum), priming (neocortex), and classical conditioning (cerebellum or amygdala).
Each branch is defined by brain biology, not just behaviour. That’s what makes the model useful for diagnosis and rehabilitation.
Strengths and Limitations
The taxonomy has real strengths, but it also faces genuine challenges:
- Strong Neuropsychological Support: Selective, and especially double, dissociations in amnesic patients are hard to explain unless declarative and non-declarative memory are genuinely separate systems.
- Biological Grounding: Each branch maps onto identifiable brain structures, which lets the taxonomy make testable clinical predictions rather than just describing behaviour.
- Overlapping Systems: Semantic memory seems built from many episodic experiences, and declarative knowledge can turn procedural with practice, so the systems aren’t fully separate.
- Reliance on Single Cases: Much of the evidence comes from a small number of brain-damaged patients, such as H.M., whose lesions were rarely clean or fully documented.
- Two Competing Taxonomies: Tulving’s content-based scheme (episodic, semantic, procedural) and Cohen and Squire’s access-based scheme (declarative vs non-declarative) divide memory along different axes, and it’s not settled which cut is more fundamental.
Frequently Asked Questions
What are the two components of declarative memory?
Declarative memory, a part of long-term memory, is composed of two components: semantic memory and episodic memory.
Semantic memory refers to our memory for facts and general knowledge about the world, while episodic memory relates to our ability to recall specific events, situations, and experiences that have happened in our personal past.
What is the difference between declarative and nondeclarative memory?
Declarative memory, also known as explicit memory, involves the conscious recall of facts (semantic memory) and events (episodic memory). In contrast, non-declarative or implicit memory involves unconscious recall and influences our behavior without awareness.
It includes procedural memory (skills and habits), priming (changes in perception and belief caused by prior exposure), and classical conditioning (learned responses to stimuli).
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