Types of Memory

Types of Memory

Memory actually takes many different forms. We know that when we store a memory, we are storing information. But, what that information is and how long we retain it determines what type of memory it is. The biggest categories of memory are short-term memory (or working memory) and long-term memory, based on the amount of time the memory is stored.

Memory Types

There are two major categories of memory: long-term memory and short-term memory. To learn more, choose from the options below.

Long-Term Memory
Long-term memory is our brain's system for storing, managing, and retrieving information. Learn more about it.

Short-Term Memory 
Closely related to "working" memory, short-term memory is the very short time that you keep something in mind before either dismissing it or transferring it to long-term memory.

Types of Long-Term Memory

As you would imagine, long-term memories are much more complex than short-term ones. We store different types of information (procedures, life experiences, language, etc.) with separate memory systems.

Explicit Memory
Explicit memory, or declarative memory, is a type of long-term memory requiring conscious thought. It's what most people have in mind when they think of a memory.

Implicit Memory
Implicit memory is a major form of long-term memory that does not require conscious thought. It allows you to do things by rote.

Autobiographical Memory
Most of us have one part of life that we remember better than others. Find out if you have a "memory bump"! 

Long-Term Memory

A long-term memory is anything you remember that happened more than a few minutes ago. Long-term memories can last for just a few days, or for many years.

Long-term memories aren't all of equal strength. Stronger memories enable you to recall an event, procedure, or fact on demand—for example, that Paris is the capital of France. Weaker memories often come to mind only through prompting or reminding.

Long-term memory isn't static, either. You do not imprint a memory and leave it as if untouched. Instead, you often revise the memory over time—perhaps by merging it with another memory or incorporating what others tell you about the memory. As a result, your memories are not strictly constant, and are not always reliable.

There are many different forms of long-term memories. These memories aren't formed and retained in a single part of the brain; instead, the process of creating and storing long-term memories is spread throughout multiple regions. The two major subdivisions are explicit memory and implicit memory. Explicit memories are those that you consciously remember, such as an event in your life or a particular fact. Implicit memories are those that you do without thinking about, like riding a bike—you once learned how, and you remembered how, but now do it without conscious thought. Although understanding these differences in the types of long-term memory is helpful, the divisions are fluid: different forms of memory often mix and mingle.

To learn more about the different types of long-term memory, view our explicit (declarative) memory and implicit (nondeclarative) memory pages.

Short-term memory

Short-term memory—closely related to "working memory"—is like a receptionist for the brain. As one of two main memory types, short-term memory is responsible for storing information temporarily and determining if it will be dismissed or transferred on to long-term memory. Although it sounds complicated, this process takes your short-term memory less than a minute to complete. For example, it is helping you right now by storing information from the beginning of this sentence, so that you can make sense of the end of it. More recently, scientists have begun to dive a little deeper into "short-term" brain functions and have added a separate (but similar) type of memory,"working" memory.

Working Memory vs. Short-Term Memory

Working memory is a newer concept than short-term memory. The two are often used interchangeably; however, working memory emphasizes the brain's manipulation of information it receives (using it, storing it, and so on), while short-term memory is a more passive concept. Working memory is often thought of as the brain's "scratch pad" that keeps information – a number, name, or whatever else – on hand just long enough to use.

Age and Short-Term Memory

As we grow older, the amount of time our short-term memory can store information becomes shorter and shorter. Age, and other clinical conditions, makes us more likely to have trouble keeping up with certain tasks, like remembering which button to push in a bank's phone menu. It also gives our brains less time to successfully move new information to long-term memory, making us more likely to forget details of recent events. Memory lapses and cognitive decline are a normal part of aging. Although this is a normal part of aging, you can work towards slowing down the process by. However, you can work towards slowing down the process by maintaining a brain-healthy lifestyle and keeping your memory active.

Explicit Memory

Explicit memory (also called "declarative memory") is one of the two major subdivisions of long-term memory. Explicit memory requires conscious thought—such as recalling who came to dinner last night or naming animals that live in the rainforest. It's what most people have in mind when they think of "memory," and whether theirs is good or bad. Explicit memory is often associative; your brain links memories together. For example, when you think of a word or occasion, such as an automobile, your memory can bring up a whole host of associated memories—from carburetors to your commute to a family road trip to a thousand other things.

Episodic Memory

Episodic memory is one type of explicit memory. Episodic memory is autobiographical: it provides us with a crucial record of our personal experiences. It is our episodic memory that allows us to remember the trip we took to Vegas, what we had for dinner last night, who told us that our friend Maryann was pregnant. Any past event in which we played a part, and which we remember as an "episode" (a scene of events) is episodic. How well we record an episodic memory depends on several factors. For example, things that occur to us in emotionally charged conditions are often stronger memories. Most people remember where they were when they heard about the World Trade Center on 9/11, or the details of a wedding of a loved one, because those were highly emotional moments for them. This form of memory appears to be centered in the brain's hippocampus—with considerable help from the cerebral cortex. Read more about this type of autobiographical memory and take a test to see if your episodic memories center in the same time of life as the average person's.

Semantic Memory

Another type of explicit memory is semantic memory. It accounts for our "textbook learning" or general knowledge about the world. It's what enables us to say, without knowing exactly when and where we learned, that a zebra is a striped animal, or that Paris is the major city in France. Scientists aren't sure where semantic memory happens in the brain; some say in the hippocampus and related areas, while others think it's widely spread throughout the brain. As with episodic memory, semantic memory ranges from strong (recall) to weak (familiarity). Unlike episodic memory, semantic memory is better sustained over time. We are often able to retain a highly functioning semantic memory into our 60's–after which it undergoes a slow decline.

Implicit Memory

Implicit memory (also called "nondeclarative" memory) is a type of long-term memory that stands in contrast to explicit memory in that it doesn't require conscious thought. It allows you to do things by rote. This memory isn't always easy to verbalize, since it flows effortlessly in our actions.

Procedural Memory

Procedural memory is the type of implicit memory that enables us to carry out commonly learned tasks without consciously thinking about them. It's our "how to" knowledge. Riding a bike, tying a shoe and washing dishes are all tasks that require procedural memory. Even what we think of as "natural" tasks, such as walking, require procedural memory. Though we can do such tasks fairly easily, it's often hard to verbalize exactly how we do them. Procedural memory likely uses a different part of the brain than episodic memory—with brain injuries, you can lose one ability without losing the other. That's why a person who has experienced amnesia and forgets much about his or her personal life often retains procedural memory: how to use a fork or drive a car, for example.

Priming

Implicit memory can also come about from priming. You are "primed" by your experiences; if you have heard something very recently, or many more times than another thing, you are primed to recall it more quickly. For instance, if you were asked to name an American city that starts with the letters "Ch," you would most likely answer Chicago, unless you have a close personal connection to or recent experience with another "Ch" city (Charlotte, Cheyenne, Charleston…) because you've heard about Chicago more often. In the brain, the neural pathways representing things we have experienced more often are more salient than those for things with which we have fewer experiences. As with short-term memory, long-term memory can weaken with age or with cognitive conditions. For example, it can be harder to complete a procedure that was previously quite easy for you. You might forget a step to baking a cake you've baked a hundred times, and that you thought you had firmly committed to memory.