Long-term Memory

Memory Opens in new window is the capacity to acquire, store, and retrieve information. It is composed of multiple systems and processes, with different functional roles and anatomical substrates.

One of the main dissociations in memory concerns the duration of storage systems. Short-term memory Opens in new window holds information active in the mind over limited time periods, while long-term memory, the focus of this study, stores information durably.

Definition and Overview

Accordingly, LTM may be described as an “archive” of information about past events in our lives and knowledge we have learned.

What is particularly amazing about this storage is how it stretches from just a few moments ago to as far back as we can remember. Many of us can recall quite vividly events from our childhoods or facts learned decades ago in school.

Long-term-memory, therefore, is a memory system that is capable of storing data for months or years.

To ascertain the large time span of LTM, we look at what John, a fictitious student, who has just taken a seat in class might be remembering about events that occurred at various times in the past.

His first recollection—that he has just sat down—would be contained in his short-term/working memory because it happened within the last 30 seconds.

But everything before that—from his recent memory that 5 minutes ago he was walking to class, to a memory from 10 years earlier of the elementary school he had attended in the third grade—is part of long-term memory.

Although all of these memories are contained in long-term memory (LTM), they aren’t all the same.

More recent memories tend to be more detailed, and much of this detail and often the specific memories themselves fade with the passage of time and as other experiences accumulate.

Thus, on October 1, 2006, John would probably not remember the details of what happened while walking to class on October 1, 2005, but would remember some of the general experiences from around that time.

But simply considering long-term memory as an “archive” that retains information from the past leaves out an important function of LTM.

Consider, for example, what happens when John’s friend says, “Jim and I saw the new James Bond movie last night”.

As John’s working memory Opens in new window is holding the exact wording of that statement in his mind, it is simultaneously accessing information from long-term memory, which helps him understand what Cindy is saying.

John’s ability to understand the sentence depends on retrieving Opens in new window, from LTM, the meanings of each of the words that make up the sentence.

His LTM also contains a great deal of additional information about movies, James Bond, and Cindy.

Although John might not consciously think about all of this information (after all, he has to pay attention to the next thing that Cindy is going to tell him), it is all there in his LTM and adds to his understanding of what he is hearing and his interpretation of what that might mean.

Once information is stored in long-term-memory, it may well persist for a lifetime.

As is the case for memory in general, long-term memory has several distinct types. In the next study Opens in new window, we take a survey of the long-term memory systems Opens in new window.