Long-term memory refers to the storage of information in memory over an extended period of time. Having long-term memory allows people to remember events in their lives and various facts and concepts learned throughout their lifespan.
Researchers Richard Atkinson and Richard Shiffrin proposed one of the first models of long-term memory in 1968.
It is sometimes referred to as a multi-store model because it divides memory into different components, called stores: sensory store, short-term store (called working memory or short-term store), and long-term store.
Since the Atkinson and Shiffrin model was originally proposed, it has been well-researched, expanded and refined.
Research has added several types of long-term memory (Malmberg et al., 2019) and identified neurological concomitants that are involved in the long-term storage of information in the brain (Voss & Paller, 2008).
Today, we divide long-term memory into six types.
Types of Long-Term Memory
The graphic below identifies the types of long-term memory. There are two main divisions: explicit and implicit, and each of those are further divided into additional subtypes.
See Also: Types of Short-Term Memory
1. Explicit Memory
Explicit memory, also known as declarative memory, is a type of long-term memory that requires conscious thought. It includes memories that are easily verbalized, such as facts (semantic memory) or personal experiences and events (episodic memory).
This type of memory is formed and retrieved through conscious, intentional processes. The formation of explicit memory involves regions of the brain such as the hippocampus and the medial temporal lobe.
Explicit memory’s vital role in our daily function is to allow us to remember past experiences and use them to plan and anticipate future events (Tucker, Luu, & Johnson, 2022).
Explicit memory is further is divided into two subtype: semantic and episodic, as outlined below.
Explicit Memory Example
An example of explicit memory is recalling specific details about an academic lecture you attended last week. This involves the conscious recollection of factual information and events (Tucker, Luu, & Johnson, 2022).
2. Semantic Memory
Semantic memory is a type of explicit memory. It refers to our general world knowledge that we have accumulated throughout our lives (Tulving, 1973).
Levy provides a simple definition:
“Semantic memory consists of your entire knowledge base including your vocabulary, concepts, and ideas.”(Levy, 2013, p. 206)
Semantic memory is an organized record of facts, concepts, and skills that we have acquired.
This type of memory includes information such as vocabulary, conceptual knowledge, and facts like “Paris is the capital of France.” It is a component of our long-term memory that is not related to personal experiences.
Semantic Memory Example
An example of semantic memory is knowing that the Earth revolves around the Sun. This type of memory is about general world knowledge that we have amassed over our lifetime (Cohen & Squire, 2017).
3. Episodic Memory
Memories about events that we experience, such as a vacation or business meeting, are stored in episodic memory. Kearns and Lee (2015, p. 171) provide a simple definition, claiming episodic memory is “memory for events in a particular time and place.”
Being able to recall who said what and the sequence of issues discussed during last week’s meeting is an example of episodic memory.
Endel Tulving (1972; 1983), one of the most influential memory researchers, provided insights into the relationship between semantic and episodic memory that still hold true today:
“…one system can operate independently of the other,” and most likely are “governed at least partially by different principles” (1983, p. 66), although both systems are “closely interdependent and interact with one another virtually all the time” (1983, p. 65).
Episodic Memory Example
An example of episodic memory is remembering your first day at school, including the feelings, people, and places associated with that particular event. This involves the recollection of autobiographical events located in time and space (Tulving, 2010).
4. Implicit memory
Sometimes referred to as nondeclarative memory, implicit memory refers to information that is remembered unconsciously and without effort.
Schacter et al. (1993) explain:
“Various types of perceptual, motor, and cognitive skill learning can also be considered expressions of implicit memory, in that they can occur without reference to, or recollection of, prior learning episodes.”(Schacter et al., 1993, p. 160-161)
Even though information in implicit memory is retrieved without intention, it can still affect behavior.
Implicit memory is also divided into two subtypes: procedural and emotional.
Implicit Memory Example
An example of implicit memory is your ability to ride a bicycle even if you haven’t done it for years. This memory deals with learned skills that occur without conscious awareness (Gabrieli, 1998).
5. Procedural Memory
Procedural memory refers to knowledge about how to do things. It occurs when we play a musical instrument or operate machinery – both tasks that require a procedure, or ‘how to’.
Spielman (2017) argues that procedural memory “is the memory for skilled actions, such as how to brush your teeth, how to drive a car, how to swim the crawl (freestyle) stroke” (Spielman, 2017, p. 259)
Procedural memory is often outside of our consciousness, such as when we ride a bike, and we’re doing a wide range of tasks such as balancing, steering by leaning, and pedaling all at once.
Much of what we know about procedural memory comes from neuroscience and 50 years of research on one individual known as patient H. M. See the Case Study box below for more information about patient H. M.
Procedural Memory Example
An example of procedural memory is knowing how to drive a car. It refers to motor skills and habits that are automatic and learned through repetition (Anderson, 2010).
6. Emotional Memory
Emotional memory is a function of conditioning. Reexperiencing intense feelings of fear that occurred when encountering a dangerous situation is an example of emotional memory.
Although this seems very similar to episodic memory, it contains the more emotional dynamics of the experience that are activated automatically, without conscious intent.
Unlike episodic memory, where the focus is on recalling the details of the event, emotional memory is more geared towards the affective component of an experience, encompassing feelings and emotional reactions.
This aspect of memory is activated without conscious intent, making it an automatic, reflexive process.
These emotionally-rooted memories can have profound influence on our behavior and decisions, acting as implicit guides in similar future situations by conditioning us to avoid potential threats or seek rewarding stimuli.
Emotional Memory Example
An example of emotional memory is feeling anxious when you see a dog because you were bitten by one as a child. This refers to conditioned, automatic emotional responses to certain stimuli.
Key Characteristics of Long-Term Memory
There are several key characteristics of long-term memory. First and foremost, long-term memory has, theoretically, unlimited capacity and unlimited duration.
This means that students should be able to remember everything they study. As long as it is committed to long-term memory in the first place, it can be retrieved, forever.
Of course, that is the way long-term memory works theoretically. Usually however, not everything a person has stored in long-term memory is there forever. There are several phenomena that disrupt permanent storage.
- Information Decay: Sometimes information stored in long-term memory decays (Baddeley et al., 2009). If information is not used periodically, then it becomes weaker and will eventually disappear. Research has identified a neurological basis for decay (ALong-term memoryann & Schunn, 2012; Richards & Frankland, 2017).
- Interference: Sometimes information stored in long-term memory interferes with the retrieval of other information in storage (Underwood, 1957; Raaijmakers & Jakab, 2013). When information recently acquired is stored over previous information, it is called retroactive interference. The new information kind of “pushes out” the old information and replaces it with the newly learned material.
Conversely, when previously stored information interferes with remembering newly acquired material, it is called proactive interference.
Interference of Long-Term Memory: How does this Work?
That there is still considerable debate as to the exact mechanism behind interference, where long-term memory is displaced, disrupted, or inhibited (see Raaijmakers & Jakab, 2013).
Different researchers have proposed and tested various competing explanations.
- Memory disruption: The competition theorists argue that interference occurs due to a disruption of retrieval processes (Mensink & Raaijmakers, 1988; Raaijmakers, 2008).
- Memory repression: A popular competing account is referred to as the inhibition theory (Anderson et al., 1994). The inhibition theory postulates that in order to retrieve information X, previously stored information Y, must be repressed. The more times information Y is repressed, the weaker its memory trace becomes.
Ultimately, Raaijmakers and Jakab (2013) state: “We conclude that despite the large amount of research over the past 15 years, there has been no clear resolution…” (p. 23).
Case Study: The Story of Patient H. M.
For over 50 years, neuroscientists conducted tests on patient H. M. His cognitive abilities were examined extensively and led to many insights into how the brain organizes different types of memory.
As a young child, H. M. began experiencing minor seizures due to a bicycle accident when he was 10. Over the subsequent 15+ years, the seizures became more frequent and more intense. Eventually he had to stop working at the age of 27.
Because doctors needed to conduct surgery on his brain to reduce the seizures, some types of his memory were impaired. For example, he was unable to remember the names of people he had just met.
However, surprisingly, his procedural memory remained intact. He was able to remember how to do many tasks that he had learned before the surgery, and able to learn how to perform new tasks.
For instance, one test involved using a mirror to draw the outline of a star. Although he was able to master this task, “…at the end of testing, he had no recollection of having done the task before” (Squire, 2009, p. 8).
“The findings from H.M. established the fundamental principle that memory is a distinct cerebral function, separable from other perceptual and cognitive abilities…” (p. 6).
Long-term memory (long-term memory) refers to information stored over a long period of time. It is divided into several types and subtypes that include memory for facts, personal life experiences, how to do things, and the emotional dynamics of previous events.
Long-term memory is utilized everyday of our lives. It is involved in taking exams, remembering what people said at meetings, driving our cars, and the intense feelings we have associated with certain situations and other people in our lives.
What scientists have learned about long-term memory has implications in both education (see: neuroeducation) and the legal system.
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Appendix: Description of Image
Top Level Heading: Long-term Memory
Sub-Category 1: Explicit Memory (conscious effort)
Types of Explicit Memory: Semantic Memory (facts and general knowledge) and Episodic Memory (events and experiences)
Sub-Category 2: Implicit Memory (without conscious effort)
Types of Implicit Memory: Procedural Memory (motor skills) and Priming (enhanced activation)
Dr. Chris Drew is the founder of the Helpful Professor. He holds a PhD in education and has published over 20 articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education. [Image Descriptor: Photo of Chris]