By: Donald Clark
TheThree Memory Storage Systems
In cognitive psychology, memory is usually divided into three stores: the sensory, the short-term, and the long-term. The progress of information through these stores is often referred to as:
The Information Processing Model
The sensory memory retains an exact copy of what is seen or heard (visual and auditory). It only lasts for a few seconds, while some theorize it last only 300 milliseconds. It has unlimited capacity.
Short-Term Memory (STM)
Selective attention determines what information moves from sensory memory to short-term memory. STM is most often stored as sounds, especially in recalling words, but may be stored as images.
Works like RAM memory in computers; provides a working space. Is thought to be 7 bits in length, that is, we normally only remember 7 items. STM is vulnerable to interruption or interference.
Long-Term Memory (LTM)
This is relatively permanent storage. Information is stored on the basis of meaning and importance.
Short-Term Memory (STM)
STM is characterized by:
After entering sensory memory, a limited amount of information is transferred into short-term memory. Within STM, there are three basic operations:
The process of transferring information from STM to LTM involves the encoding or consolidation of information. This is not a function of time, that is, the longer a memory stayed in STM, the more likely it was to be placed into LTM; but on organizing complex information in STM before it can be encoded into LTM. In this process of organization, the meaningfulness or emotional content of an item may play a greater role in its retention into LTM. As instructional designers, we must find ways to make learning relevant and meaningful enough for the learner to make the important transfer of information to long-term memory.
Also, on a more concrete level, the use of chunking (Reigeluthís Elaboration Theory) has been proven to be a significant aid for enhancing the STM transfer to LTM. Remember, STM’s capacity is limited to seven items, regardless of the complexity of those items. Chunking allows the brain to automatically group certain items together.
George Miller’s classic 1956 study found that the amount of information which can be remembered on one exposure is between five and nine items, depending on the information.
Applying a range of +2 or -2, the number 7 became known as Miller’s Magic Number, the number of items which can be held in Short-Term Memory at any one time.
Miller himself stated that his magic number was for items with one aspect. His work is based on subjects listening to a number of auditory tones that varied only in pitch. Each tone was presented separately, and the subject was asked to identify each tone relative to the others she had already heard, by assigning it a number. After about five or six tones, subjects began to get confused, and their capacity for making further tone judgments broke down.
He found this to be true of a number of other tasks. But if more aspects are included, then we can remember more, depending upon our familiarity and the complexity of the subject (in Miller’s research, there was only one aspect — the tone). For example, we can remember way more human faces as there are a number of aspects, such as hair color, hair style, shape of face, facial hair, etc.
We remember phone numbers by their aspects of 2 or more groupings. We don’t really remember “seven” numbers. We remember the first group of three and then the other grouping of four numbers. If it is long distance, then we add an area code. So we actually remember 10 numbers by breaking it into groups of three. Social Security numbers work on the same principle — xxx-xx-xxxx (3 groups of numbers). Also, I’m not sure why we have seven numbers in the phone system. The author states it is not based upon Miller’s work, but never states why.
Our prior knowledge of pictures and faces allow us to see a “face” in the word “Liar”.
Long-Term Memory (LTM)
The knowledge we store in LTM affects our perceptions of the world, and influences what information in the environment we attend to. LTM provides the framework to which we attach new knowledge. It contrasts with short-term and perceptual memory in that information can be stored for extended periods of time and the limits of its capacity are not known.
Schemas are mental models of the world. Information in LTM is stored in interrelated networks of these schemas. These, in turn, form intricate knowledge structures. Related schemas are linked together, and information that activates one schema also activates others that are closely linked. This is how we recall relevant knowledge when similar information is presented. These schemas guide us by diverting our attention to relevant information and allow us to disregard what is not important.
Since LTM storage is organized into schemas, instructional designers should activate existing schemas before presenting new information. This can be done in a variety of ways, including graphic organizers, curiosity-arousing questions, movies, etc.
LTM also has a strong influence on perception through top-down processing – our prior knowledge affects how we perceive sensory information. Our expectations regarding a particular sensory experience influence how we interpret it. This is how we develop bias. Also, most optical illusions take advantage of this fact.