What Is Long-Term Memory

What Is Long-Term Memory?

Long-term memory is usually considered a system with a vast, seemingly unlimited capacity for storing the experiences we go through and the information we learn. It can retain memories for long periods of time, ranging from days to an entire lifetime. You might still remember the answer to a trivia question you heard on TV as a kid, or a door number you once noticed on the street.

Long-term memory provides us with the ability to remember information or knowledge we've learned at some point in the past. For instance, when we meet someone we know, it's our long-term memory that allows us to identify who they are as well as the details of our past interactions with them. This enables us to initiate small talk and continue the conversation without much difficulty. In addition, if we didn't have long-term memory, life would be very complicated, since we'd have to relearn everything that we learned in everyday life time and time again.

Short-Term Memory vs. Long-Term Memory

The Interaction Between Short-Term and Long-Term Memory

Short-term memory and long-term memory do not conflict with each other. Instead, they work together like a two-stage relay. Information that you see, hear, or experience is first processed by short-term memory. It holds that information for a brief period and helps filter what should be retained.

The brain decides whether to store information based on several factors:

• whether it is meaningful
• whether it is repeated
• whether it carries emotional significance
• whether it is associated with something you already know

For example, under normal circumstances, you would hardly remember a stranger’s phone number right away. But if it belongs to your crush, you are more likely to pay extra attention to it and remember at least part of it. If the brain considers the information important, it will then encode it into long-term memory.

Conversely, long-term memory also supports short-term memory. Having knowledge of certain concepts will help when trying to learn about new things that are related to them.

Key Types of Long-Term Memory

There are two main types of long-term memory: Declarative memory and Non-declarative memory.

Declarative Memory

Declarative memory, also called explicit memory, is the kind of memory people can consciously recall. It can be further divided into two types: Episodic memory and Semantic memory.

Episodic memory is about personal experiences, like your graduation ceremony. Semantic memory is about facts, concepts, and the meanings of words that you‘ve learned. For example, knowing that Paris is the capital of France is semantic memory, while remembering yourself sitting in a classroom and learning that fact belongs to episodic memory.

Non-Declarative Memory

Non-declarative memory is also called implicit memory. This is the kind of memory you use without really thinking about it. For example, typing or riding a bike are skills you can perform automatically. It also includes learned associations and habits, like getting used to using certain objects in a particular environment. This type of memory usually lasts longer than many other kinds of memory.

How Memories Become More Lasting

Short-term memory plays an important role in helping encode critical information into long-term memory by consolidating those memories. Consolidation happens on both the cellular and systems level. Cellular consolidation, where neurons are forming connections to each other, occurs within minutes to hours of the time of the original input. Systems consolidation, whereby memories are strengthened across various parts of the brain, takes longer to occur.

After a memory has been consolidated, continued use of the memory will strengthen the neural pathways associated with that memory and make it easier to retrieve later on. Conversely, a memory that is rarely accessed will become increasingly difficult to access over time. Additionally, specifically because they are encoded more deeply than other types of memories, memories with high emotional salience are often easier to recollect.

Why Do Some Long-Term Memories Fade?

Although long-term memory can be stored for many years, it sometimes fades or may even be lost. Common reasons include:

1. You rarely use the information, so it becomes harder to retrieve.
2. New information may interfere with existing memories.
3. The memory was not strongly formed in the first place.
4. Ageing or brain injury.
5. Lack of sleep, stress, and other factors.

What we need to pay attention to is that, most of the time, memories do not simply disappear; they just become temporarily inaccessible.

Can Long-Term Memory Be Wrong?

It is surprising that long-term memory can sometimes be unreliable. It is fragile and can easily be distorted by misinformation. As a result, people may misremember past experiences or even form false memories.

In a study conducted by Elizabeth Loftus, they inserted one fabricated event into three true childhood memories. About 30% of participants recalled the false event detail during the first interview, and 25% continued to report it in follow-ups. Although the sample size was relatively small, the findings suggest that a false event, especially when a relative involved, can be implanted into long-term memory.

But why does this happen? One reason is that the brain tends to look for consistency. When we do not have all the information, it may fill in the gaps with details that seem reasonable. Long-term memory can sometimes add these extra details to help the brain make sense of the whole story, which may lead to inaccurate memories.

Common Myths about Long-Term Memory

Hypnosis recovers lost memories
Hypnosis is often believed to help people recall deeply buried memories. However, it may also lead to the creation of false memories. There have been cases that psychiatrists planted traumatic experiences to patients during therapy, causing lasting psychological harm.

Flashbulb memories are accurate
When you “see” flash scenes, such as exactly where you were during an event, the memory feels so vivid that it seems impossible to be wrong. However, as mentioned before, the brain may make up these imagined details in order to maintain memory consistency.

Memory loss is inevitable with age
Although people may learn new things more slowly and experience some memory decline as they age, serious memory loss is not inevitable.