Types of Long-Term Memory: The 2 Main Types, With Examples

There are two main types of long-term memory. Explicit (declarative) memory is what you can consciously recall and put into words, and it splits into episodic memory (events you experienced) and semantic memory (facts and concepts). Implicit (nondeclarative) memory shows up in what you do rather than what you can say, and it includes procedural memory (skills and habits), priming, and classical conditioning.

Knowing the difference is more than a psychology-exam definition. Each type is learned in a different way. Reading a page of notes builds one kind of memory, practicing a clinical skill builds another, and the familiar feeling you get from rereading can fool you into thinking you've learned something you can't recall.

This guide covers each type with examples, the famous patient whose case first showed they are separate, and what each one means for how you study.

What are the types of long-term memory?

This taxonomy is mainly the work of Larry Squire and colleagues, who describe declarative memory as the capacity to consciously recollect facts and events, and nondeclarative memory as a mixed collection of unconscious learning abilities that show up in performance. The episodic vs semantic split comes from Endel Tulving, who first proposed it in the early 1970s.

Many intro courses simplify the list to three: episodic, semantic, and procedural. That's fine for a quick answer, but priming and conditioning are part of implicit memory too.

How do we know these are separate memory systems?

Much of the evidence comes from one patient, Henry Molaison, known in research papers as H.M. In 1953, at age 27, he had parts of his medial temporal lobes, including much of the hippocampus, removed on both sides to relieve severe epilepsy. Afterward he could no longer form new conscious memories, even though his intelligence and perception were intact.

Then came the surprise. H.M. learned a hand-eye coordination task called mirror drawing, tracing a shape while watching his hand only in a mirror, and got better over several days. Each day, he had no memory of having practiced before.

Later studies found the same pattern in other patients with amnesia. In 1980, Neal Cohen and Larry Squire showed that amnesic patients learned to read mirror-reversed words at the same rate as healthy people and kept the skill for at least three months, while having poor memory for the task itself. They described the difference as "knowing how" versus "knowing that."

The conclusion: conscious memory for facts and events depends on the hippocampus and nearby structures, while skills, habits, and priming rely on other brain systems. Habit learning, for example, depends heavily on a structure called the striatum.

Why this matters for you: knowing the steps of a skill and being able to do it are stored separately. Reading about a procedure won't make you fluent at it, and being fluent won't guarantee you can explain it on a written exam. If your course tests both, practice both.

Explicit (declarative) memory

Explicit memory is what most people mean by "memory": things you can bring to mind on purpose and describe. These memories are flexible: you can compare them, recombine them, and apply them to new questions. It's also the system most exams test.

Episodic memory

Episodic memory stores events you personally experienced, anchored to a time and place: the conversation with your lab partner, the morning of your driving test, the lecture where something finally made sense.

Example: you remember sitting in the third row while your professor sketched the Krebs cycle on the whiteboard, and the marker running out halfway through.

Semantic memory

Semantic memory stores general knowledge: facts, concepts, vocabulary, rules. You know that Paris is the capital of France, but you probably don't remember the moment you learned it.

Example: you know the Krebs cycle produces NADH and FADH₂ for the electron transport chain, without recalling where you learned it.

Episodic vs semantic memory

Most exam content needs to end up semantic: usable without remembering the lecture it came from. Episodic memories make good hooks, though. A vivid demo or case is easier to recall, and retrieving the idea behind it again and again turns it into general knowledge.

How long can semantic memory last? In a study of 733 people who had learned Spanish in school, Harry Bahrick found that retention fell for the first 3 to 6 years, then held steady for up to 30 years. That shape, a steep early drop that levels off, echoes the Ebbinghaus forgetting curve, stretched over years instead of days.

What best predicted how much survived was how well the Spanish had been learned in the first place: how many courses people took and the grades they earned. The effort you put into learning a subject properly now decides how much of it you'll still have years later. For why the rest fades, see why we forget.

Implicit (nondeclarative) memory

Implicit memory changes your behavior without you being aware of remembering. You show it by doing, not by describing.

Procedural memory

Procedural memory stores skills and habits: typing, driving, playing scales, and also cognitive skills like solving a familiar type of equation or reading an ECG. It builds gradually through practice, and once learned it runs with little conscious effort.

That's the goal for any skill on your exam. A nursing student who has practiced taking a blood pressure many times doesn't have to think through each step under pressure, which leaves attention free for the patient. Deliberate practice explains how to practice skills so they improve, not just repeat.

One caution from the research: skills learned purely through implicit learning can be rigid. In Squire and Wixted's review, profoundly amnesic patients eventually learned a set of object discriminations to over 90% accuracy, after more than 1,000 trials (healthy people needed fewer than 80). But their performance collapsed when the task format changed. Understanding why a procedure works (explicit knowledge) helps you adapt it to new problems.

Priming

Priming is when earlier exposure to something makes you process it faster or more easily later, often without noticing. In one study, people with amnesia named pictures about 100 milliseconds faster if they had seen them before, even when they couldn't recognize them as familiar.

Priming matters for students because of what it feels like. After rereading a chapter, the words and diagrams feel easy and familiar. That ease is real, but it isn't the same as being able to recall the material on a blank exam page. This is the core reason active recall beats passive reading.

Classical conditioning

Classical conditioning is learning an automatic response to a cue that has been paired with something else, as in Pavlov's dogs salivating at a sound that predicted food. In students, it often shows up as emotional reactions: a tight chest when you open a subject you failed before, or calm when you sit at your usual study desk. If the exam room itself triggers panic, managing test anxiety covers practical fixes.

Explicit vs implicit memory: key differences

What each memory type means for studying

Three habits follow from this:

1. Turn episodes into knowledge. After a memorable lecture or lab, write the principle it illustrated from memory that evening, then recall it again a few days later. Our guide to spaced repetition shows how to schedule those reviews.
2. Practice skills as skills. Watching worked solutions builds explicit knowledge of the steps. Only doing the problems builds the procedure. Interleaving different problem types helps you learn when to use each one.
3. Distrust easy familiarity. If a page feels known, close it and try to reproduce it. What you can produce is what you know.

Worked example: one topic, three memory types

A nursing student learning blood pressure measurement uses all three:

• Semantic: normal and abnormal ranges, what the Korotkoff sounds mean, common sources of error. Learn these with flashcards and self-quizzing.
• Episodic: the skills-lab session where the cuff was too small and the reading came out high. Use that memory as a hook for the rule "check cuff size."
• Procedural: cuff placement, inflation, listening while deflating. Build this with repeated hands-on practice and feedback until it runs smoothly.