Memory is the vital link between the learner learning/retaining information and the cognitive process of applying what is learned. It is the ability of people and other organisms to encode (initial perception and registration of information), store (retention of encoded information over time), and retrieve (processes involved in using stored information) information. [Figure] When a person successfully recalls a past experience (or skill), information about the experience has been encoded, stored, and retrieved.

Learning Process, Aviation Instructor
Information processing within the sensory register, working on short-term memory, and long-term memory includes complex coding, sorting, storing, and recall functions

Although there is no universal agreement of how memory works, a widely accepted model has three components: sensory memory, short-term memory (STM), and long-term memory (LTM).

Sensory Memory

Sensory memory is the part of the memory system that receives initial stimuli from the environment and processes them according to the individual’s preconceived concept of what is important. Other factors can influence the reception of information by sensory memory. For example, if the input is dramatic and impacts more than one of the five senses, that information is more likely to make an impression. The sensory memory processes stimuli from the environment within seconds, discards what is considered extraneous, and processes what is determined by the individual to be relevant. This is a selective process where the sensory register is set to recognize certain stimuli and immediately transmit them to the STM for action. The process is called precoding. An example of sensory precoding is recognition of a fire alarm. No matter what is happening at the time, when the sensory register detects a fire alarm, the working memory is immediately made aware of the alarm and preset responses begin to take place. Sensory memory is capable of retaining information for only a very short period of time and within seconds the relevant information is passed to the STM.

Short-Term Memory (STM)

Short-term memory is the part of the memory system where information is stored for roughly 30 seconds, after which it may rapidly fade or be consolidated into long-term memory, depending on the individual’s priorities. Several common steps help retention in STM. These include rehearsal or repetition of the information and sorting or categorization into systematic chunks. The sorting process is usually called coding or chunking. A key limitation of STM is that it takes 5–10 seconds to properly code information and if the coding process is interrupted, that information is easily lost since it is stored for only 30 seconds. The goal of the STM is to put the information to immediate use.

STM is not only time-limited, it also has limited capacity, usually about seven bits or chunks of information. A seven-digit telephone number is an example. As indicated, the time limitation may be overcome by rehearsal. This means learning the information by a rote memorization process. Of course, rote memorization is subject to imperfections in both the duration of recall and in its accuracy. The coding process is more useful in a learning situation. In addition, the coding process may involve recoding to adjust the information to individual experiences. This is when actual learning begins to take place. Therefore, recoding may be described as a process of relating incoming information to concepts or knowledge already in memory.

Brain research has led to the conclusion that STM resembles the control tower of a major airport and is responsible for scheduling and coordinating all incoming and outgoing flights. STM has three basic operations: iconic memory, acoustic memory, and working memory. Iconic memory is the brief sensory memory of visual images. Acoustic memory is the encoded memory of a brief sound memory or the ability to hold sounds in STM. Of the two, acoustic memory can be held longer than iconic memory. Working memory is an active process to keep information until it is put to use (think of a phone number repeated until used). It is useful in remembering a spoken sentence or a string of digits.

Also called “scratch-pad” memory, working memory is of short duration and has limited capacity. It simultaneously stores and manipulates information. The goal of the working memory is not really to move the information from STM to LTM, but merely put the information to immediate use.

STM retention makes information available long enough for it to be rehearsed. For example, if the learner repeats the number to himself, it can be transferred to some sort of longer term storage. To retain information for extended periods of time, it needs to be transferred from STM to LTM. This process involves encoding or consolidation of information into LTM where it can then be retrieved.

Long-Term Memory (LTM)

LTM is relatively permanent storage of unlimited information, and it is possible for memories in LTM to remain there for a lifetime. What is stored in LTM affects a person’s perceptions of the world and affects what information in the environment is noticed. Information that passes from STM to LTM typically has some significance attached to it. For example, imagine how difficult it would be for a pilot to forget the first day he or she soloed. This is a significant day in any pilot’s training, so when the information was processed, significance was attached to it, the information was deemed important, and it was transferred into LTM.

There appear to be other reasons information is transferred to LTM because the average human brain stores numerous insignificant facts. One explanation is repetition; people tend to remember things the more they are rehearsed. Information also ends up in LTM because it is somehow attached to something significant. A person may remember the color of the clothing of the recipient of a wedding proposal. The color of the clothing plays no important role, but is attached to the memory of the experience.

For the stored information to be useful, some special effort was expended during the encoding or consolidation of information in STM. The encoding should provide meaning and connections between old and new information. If initial encoding is not properly accomplished, recall is distorted and it may be impossible. The more effective the encoding process, the easier the recall. However, it should be noted that the LTM is a reconstruction, not a pure recall of information or events. It is also subject to limitations, such as time, biases, and, in many cases, personal inaccuracies. This is one reason why two people who view the same event often have totally different recollections. Memory also applies to psychomotor skills. For example, with practice, a tennis player may be able to serve a tennis ball at a high rate of speed and with accuracy. This may be accomplished with very little thought. For a pilot, the ability to instinctively perform certain maneuvers or tasks that require manual dexterity and precision, provides obvious benefits. For example, it allows the pilot more time to concentrate on other essential duties such as navigation, communications with ATC facilities, and visual scanning for other aircraft.

Information in LTM is stored in interrelated networks of schemas which are the cognitive frameworks that help people organize and interpret information. Schemas guide recognition and understanding of new information by providing expectations about what should occur. Since LTM is organized into schemas, instructors should consciously look for ways to make training relevant and meaningful enough for the learner to transfer new information to LTM. This can be accomplished by activating existing schemas before presenting new information. For example, a brief review of the previous lesson via discussion, video, questions, etc.

Remembering What Has Been Learned

The moment people learn something new and add it to their repertoire of knowledge and skill, they are confronted with a second task: the task of remembering it. Remembering is a challenge because of a natural feature of human memory-forgetting. Forgetting is such an apparent part of human memory that it is often the first thing that people think of when they bring up the topic of memory.

The following section discusses how remembering and forgetting happens in predictable ways that help keep human memories tuned to the demands of everyday life. Memories help people keep fresh precisely those things needed next, and let slip those things that have outlived their usefulness. Understanding the factors that determine what is remembered and what is forgotten helps instructor and learner get the most from memory.

How Usage Affects Memory

The ability to retrieve knowledge or skills from memory is primarily related to two things: (1) how often that knowledge has been used in the past; and (2) how recently the knowledge has been used. These two factors are called frequency and recency of use. Frequency and recency can be present individually or in combination.

Frequency and recency—knowledge that enjoys both frequency and recency is likely to be retrieved easily and quickly. This is knowledge much used in the past that continues to be used in the present. This is the ideal situation for knowledge and skills that need to be used.

Frequency only—knowledge that has been used much in the past but that has not been used recently is vulnerable to being forgotten. This type of knowledge is likely to be retrieved slowly or not at all. To retrieve this knowledge and skill, some recent rehearsal or practice needs to be added in order to refresh the memory.

Recency only—knowledge that has been recently used but has not been used in the past is knowledge that has been recently acquired. This type of knowledge is particularly vulnerable to being forgotten since there is little to distinguish it from “throw away” knowledge, such as an hourly weather broadcast. To remember this knowledge requires a program of regular rehearsal to build up its frequency.


Forgetting, which refers to loss of a memory, typically involves a failure in memory retrieval. The failure may be due to the decay or overwriting of information which has been temporarily stored in STM, but generally forgetting refers to loss of information from LTM. The information is not lost, per se, it is somewhere in the person’s LTM, but he or she is not able to retrieve and remember it.

Why do people forget? Why don’t we remember everything? Do we need to remember everything? Most of the information people are exposed to each day has a short period of usefulness with little need to retain it. For example, why would anyone need to remember the details of an hourly weather broadcast ten years ago?

Thus, forgetting knowledge is not always a bad thing. For example, forgetting old information keeps new information up to date. Many theories on why people forget have been offered to explain the phenomenon, among them retrieval failure, fading, interference, and repression or suppression.

Retrieval Failure

Retrieval failure is simply the inability to retrieve information, that tip-of-the-tongue phenomenon when a person knows the meaning of a word, or the answer to a question, but cannot retrieve it. It is also caused by the fact that sometimes people simply do not encode information well and the information never makes it to LTM or is lost before it can attach itself to the LTM. This is sometimes referred to as failure to store.


The theory of fading or decay suggests that a person forgets information that is not used for an extended period of time, that it fades away or decays. It had been suggested that humans are physiologically preprogrammed to eventually erase data that no longer appears pertinent.

On the other hand, experimental studies show that a hypnotized person can describe specific details of an event, which normally is beyond recall. Apparently the memory is there, locked in the recesses of the mind. The difficulty is summoning the memory to consciousness or retrieving the link that leads to it.


Interference theory suggests that people forget something because a certain experience has overshadowed it, or that the learning of similar things has intervened. This theory might explain how the range of experiences after graduation from school causes a person to forget or to lose knowledge. In other words, new events displace many things that had been learned. From experiments, at least two conclusions about interference may be drawn. First, similar material seems to interfere with memory more than dissimilar material; and second, material not well learned suffers most from interference.

Repression or Suppression

Freudian psychology advances the view that some forgetting is caused by repression or suppression. In repression or suppression, a memory is pushed out of reach because the individual does not want to remember the feelings associated with it. Repression is an unconscious form of forgetting while suppression is a conscious form.

Forgetting information does not mean it is gone forever. Sometimes it is still there, just inaccessible.