memory

memory


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The Three 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







Donald Hebb argued that it was doubtful that a chemical process could occur fast enough to accommodate immediate memory, yet remain stable enough to accommodate permanent memory. Hence, the present theory of three storage areas.
Sensory Memory
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.

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Short-Term Memory (STM)
STM is characterized by:

A limited capacity of up to seven pieces of independent information.

The brief duration of these items last from 3 to 20 seconds.

Decay appears to be the primary mechanism of memory loss.

After entering sensory memory, a limited amount of information is transferred into short-term memory. Within STM, there are three basic operations:

Iconic memory - The ability to hold visual images.

Acoustic memory - The ability to hold sounds. Acoustic memory can be held longer than iconic memory.

Working memory - An active process to keep it until it is put to use (think of a phone number you'll repeat to yourself until you can dial it on the phone). Note that the goal is not really to move the information from STM to LTM, but merely put the information to immediate use.
Mechanism of short-term memory loss revealed
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 (Reigeluthيs 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.
Miller's Magic Number
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.

An important factor for retention of learned information in LTM is rehearsal that provides transfer of learning.



Existence of a separate store
A classical model of memory developed in the 1960's assumed that all memories pass from a short-term to a long-term store after a small period of time. This model is referred to as the "modal model" and has been most famously detailed by Atkinson and Shiffrin (1968). The exact mechanisms by which this transfer takes place, whether all or only some memories are retained permanently, and indeed the existence of a genuine distinction between the two stores, remain controversial topics among experts.
One form of evidence, cited in favor of the separate existence of a short-term store comes from anterograde amnesia, the inability to learn new facts and episodes. Patients with this form of amnesia, typically caused by damage to the hippocampus, have intact ability to retain small amounts of information over short time scales (up to 30 seconds) but are dramatically impaired in their ability to form longer-term memories (a famous example is patient HM). This is interpreted as showing that the short-term store is spared from amnesia.
Other evidence comes from experimental studies showing that some manipulations (e.g., a distractor task, such as repeatedly subtracting a single-digit number from a larger number following learning) impair memory for the 3 to 5 most recently learned words of a list (presumably still held in short-term memory), while leaving recall for words from earlier in the list (presumably stored in long-term memory) unaffected; other manipulations (e.g., semantic similarity of the words) affect only memory for earlier list words (Davelaar et al., 2005), but do not affect memory for the last few words in a list. These results show that different factors affect short term recall (disruption of rehearsal) and long-term recall (semantic similarity). Together, these findings show that long-term memory and short-term memory can vary independently of each other. This is regarded as a double dissociation and constitutes evidence for separate systems underlying short-term and long-term memory.
Relationship to working memory
The relationship between short-term memory and working memory is differently described by various theorists, but it is generally acknowledged that the two concepts are distinct. Working memory is a theoretical framework that refers to structures and processes used for temporarily storing and manipulating information. As such, working memory might also just as well be referred to as working attention. Short-term memory generally refers in a theory-neutral manner to the short term storage of information. Thus while there are short-term memory components to working memory models, the concept of short-term memory is distinct from these more hypothetical concepts. Within one influential model of working memory (Baddeley, 1986) there are two short-term storage mechanisms: the phonological loop and the visuospatial sketchpad. Most of the research referred to here involves the phonological loop, because most of the work done on short-term memory has used verbal material.
Duration of short-term memory
The most important characteristic of a short-term store is, clearly, that it is short-term — that is, it retains information for a limited amount of time only. Most definitions of short-term memory limit the duration of storage to less than a minute; no more than about 30 seconds, and in some models as little as 2 seconds. Memory that exceeds short-term memory duration limits is known as long-term memory.
In order to overcome the limitation of short-term memory, and retain information for longer, information must be periodically repeated, or rehearsed — either by articulating it out loud, or by mentally simulating such articulation. In this way, the information will re-enter the short-term store and be retained for a further period. The process of consolidation (transfer of short-term memory to long term memory) is enhanced by the relationship, if any, of an item of short-term memory to an item in long-term memory (for example, if a sensory short-term event is linked to a trauma already in long-term memory).
The time to find a short term memory is reversely proportional to the recognition probability (see Tarnow, 2005).
Capacity of short-term memory
The second key concept associated with a short-term memory is that it has a finite capacity. Prior to the creation of current memory models, George Miller argued that human short-term memory has a forward memory span of approximately seven items plus or minus two (Miller, 1956). More recent research has shown that this magical number seven is roughly accurate for college students recalling lists of digits, but memory span varies widely with populations tested and with material. For example, the ability to recall words in order depends on a number of characteristics of these words: Fewer words can be recalled when the words have longer spoken duration; this is known as the word-length effect ( Baddeley, Thomson, & Buchanan, 1975)). Fewer words can be recalled when their speech sounds are similar to each other, this is called the phonological similarity effect ( Conrad, 1964 ). More words can be recalled when the words are highly familiar and/or occur frequently in the language (Poirier & Saint-Aubin, 1996); recall performance is also better when all of the words in a list are taken from a single semantic category (such as sports) than when the words are taken from different categories (Poirier & Saint-Aubin, 1995).
Some authors have argued that even the general intelligence factor can be understood as the channel capacity of short-term memory. In the theoretical framework of information psychology mental power, or the capacity C of short-term memory (measured in bits of information), is the product of the individual mental speed Ck of information processing (in bit/s) (see the external link below to the paper by Lehrl and Fischer (1990)), and the duration time D (in s) of information in short-term working memory, meaning the duration of memory span. Hence:
C (bit) = Ck(bit/s) × D (s).
However, against the trend of the 1950s to understand cognition in an information theoretic context, Miller himself was in doubt that the capacity of short-term memory could be measured in such a way in terms of a constant amount of information, as expressed in bits. Miller argued that the unit of measurement for short-term memory capacity is a chunk. A chunk can be a single digit or letter, it can also be a word, a multiple-digit number or even a whole phrase if the number or the phrase form a unit already learned in long-term memory before.
Chunking
Though the average person may only retain about 7±2 different units in his or her short term memory, chunking can greatly increase a person's recall ability. Through putting each unit into a meaningful word or phrase, a person's recall ability can skyrocket through practice. For example, in recalling a phone number, the person usually chunks the digits into three groups: first, the area code (such as 814), then a three digit chunk (123) and lastly a four digit chunk (4567). This method of remembering phone numbers is far more effective than attempting to remember a string of ten digits. In one testing session, an All-American cross country runner was able to recall a string of 73 digits after hearing them only once by chunking them into different running times (e.g. the first four number were 1518, a three mile time.) (Ericsson et al., 1980)
In contrast to chunking, there are also ways to lose information quickly. An example of this is interference: something that distracts a person from being able to rehearse information given to them to be remembered. This can cause a person to lose the given information much quicker than someone able to rehearse as much as they want.

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