The Stage Theory of Memory
Stage theory of memory was developed by Richard Atkinson and Richard Shiffrin in 9171. It is also called as Atkinson-Shiffrin model. As we have to store different types of memories in our daily life the stage of memory model is described as the most influential model by psychologists. It describes that there are many memory storage systems, having different properties and capacities.
The stage theory of memory assumes that humans have three-stage memory that needs our need to store information for different lengths of time. According to this stage theory, one memory holds information for brief intervals, a secondary system for less than 30 seconds, and the third is of a permanent nature.
These three storage systems have different rules and functions because we remember information for a longer time and forget the other one easily. The stage theory contains three different stages of memory systems closely linked with each other.
These three processes are encoding storage and retrieval. But, this model further classified the storage system or memory into three memories:
- Sensory memory (SM)
- Short term memory (STM) or Working memory
- Long term memory
Sensory Memory (SM)
The first memory of the stage theory of memory is the sensory memory also called sensory register holds a memory for a very brief period for further processing. Only the images of different sights, sounds, and tastes are provided in sensory memory. The information does not last long, it is like the replica of the sensory experience however it has the potential to be huge.
Sensory memory appears to last only about 0.5 of a second to 1.0 second, depending upon which sensory system is involved. The visual sensory register holds information about 1 second (Sperling, 1960) while the auditory register holds information somewhat longer about 4 to 5 seconds.
The visual sensory register has shown that it holds at least 10 to 16 items of information during the second before the information is lost. Sperling’s experiment revealed that sensory storage in visual registration seems to remain in photographic memory in the form of a faint image, called iconic image after an image disappears from vision. The duration of the icon varies approximately half a second to two seconds, depending upon the individual, the content of the image, and the circumstances.
The process of selective perception helps to attend to the stimuli. Those stimuli we pay attention to and recognize are selected from sensory memory for further processing and are transferred to short-term memory (STM). Most of the information briefly held in the sensory register is lost because it is not selected for further processing by higher centers. They are replaced by new incoming stimuli. Since the sensory register holds information for a very brief time psychologists argue to call it perception rather than memory. However, it is a stage that involves passing information from one store to the next and then retrieving the information from short-term memory to long-term memory.
Short-Term Memory (STM) or Working Memory
Many stimuli that people perceive in the course of a day are dropped out of a sensory memory system without further processing, while other stimuli make a greater impression. They are transferred for further processing. Paying attention meaningfully and rehearsal help to transfer the information, otherwise, it quickly disappears. According to stage theory, information must be processed in short-term memory (STM) before it can be transferred to move permanent storage in long-term memory.
STM as its name implies is a memory store that holds a small amount of information lasting only for a short period in consciousness. Researchers have roughly estimated it to be 10 to 30 seconds unless a person makes a deliberate effort to maintain longer by repeating it over and over again. Both children and adults have a short-term recall for roughly as many words as they can speak in 2 seconds. That is we can process only a very limited amount of information consciously. Short-term memory has limited capacity.
Psychologist George Miller (1956) demonstrated that on average, people can remember about 7 pieces of information at a time, with a normal range from five to nine items. The phone number usually is five to seven digits are an example. However, chunks can improve short-term memory. We usually find chunks in saying our phone numbers. Phone number with more than 9 items (7+/-2) are broken up by dashes (44, 34, 568) rather than with a series of individual number (4, 4, 3, 4, 5, 6, 8) when the area code is added it will be broken into more chunks. For example, at 9771-34-45-586 telephone number, there are four groups of numbers and we pause while saying numbers. These pauses separate the chunks, or group of information, which helps to increase the capacity of STM.
Rehearsal strengthens the STM. For example, after looking up a telephone number most people repeat the information over and over in their minds to prevent it from fading until it is dialed. This kind of mental or loud repetition, in order to maintain information in STM, is called maintenance rehearsal. Memorizing a poem or math formula or a definition by repeating it several times are the other examples of maintenance rehearsal. However, simply rehearsing through maintenance rehearsal does not help to transfer to LTM an elaborative rehearsal is needed.
Elaborative rehearsal involves activity thinking about the information, giving it an organization and meaning, not simply being aware of it. For example, remembering the words to a poem is much easier if a person tries to figure out its meaning and understands what it is about rather than simply memorizing by rote. Meaningfulness and understanding of the subject matter result in information to LTM promoting the transfer in a more permanent memory encoding system.
Short-term memory is also called working memory because attention and conscious effort are employed to hold the information through rehearsal. In a way, the working memory model is the second phase of STM in which we have to retrieve word meaning from LTM to make sense of new sentences or words we hear. It can be said as a central executive processor which is involved in reasoning and decision making. Working memory seems to be coordinating between STM and LTM. It contains both visual and verbal information. Visual information relates to spatial and different colors while the verbal store contains language words and numbers.
Long Term Memory (LTM)
The third step in stage memory theory stresses the importance of rehearsal or practice in processing information. Items rehearsed seem to be transferred than un-hearse items. For example, the new telephone number needs to be repeated several times in order to be remembered than just repeating it once.
The unimportant information drops out after sensory registration and STM. The important information goes to LTM. Long-term memory is a storehouse that consists of facts, images, thoughts, feelings, skills, experiences, words, languages, sentences, ideas, concepts, etc. It has limitless capacity. It is enduring and more difficult to access.
The longer the impression stays in STM the more it makes a permanent place in LTM. LTM makes it possible to retain the material for long otherwise same things needed to be learned over and over again if there would be no LTM. Psychologists have grouped long-term memory into two broad types.
- Declarative memory
- Procedural memory
The Declarative Memory
Declarative memory is a mental database of facts and rules. It is also called explicit memory. It is the predecessor of procedural knowledge which consists of places, things, meanings, and symbols. Recalling a happy memory of a picnic is a declarative memory. Both declarative and procedural memory is equally important in our everyday life.
For example, when we first learn to type, we study the layout, trying to form declarative memories of hitting the keys as to which fingers to use for each key. As we practice our speed and accuracy improves and conscious effort diminishes. This process reflects the formation of procedural memory of typing. In the end, we think of only words we want to type and no layout of the keyboard (declarative memory). This shift from conscious effortful memory to automatic procedural memory occurs in the regions of the cortex.
The declarative memory is further divided into semantic and episodic memory. Both semantic and episodic memories help to understand and gain knowledge in the process of memory.
Semantic Memory: Semantic memory consists of knowledge about the meaning of the word, sentences, ideas, concepts, languages the way words are related to one another, and the rule of using them in communication and thinking. Semantic memories stay very long, highly organized, and there is very little forgetting in the rule and meaning while using them.
Episodic Memory: Episodic memories consists of the memories of particular events, times, or places. It has a record of things that happened at certain events. Episodic memories contain our remembrance of past things. When we have to retrieve a memory from LTM it enters into consciousness, that is, into the STM, where it combines with new information that has been received, creating a new memory. If this memory is rehearsed, it may be transferred to LTM for more permanent storage.
Procedural memory is a compact or compiled form that makes little demand on attention resources. It can be utilized very quickly and efficiently. For example, driving a car and engaging in conversation with a friend, and reaching the destination without paying attention to the route. It is a skill or habit memory denoting “how to”. Likewise, our memories related to cooking, gardening, typing, bicycling are all procedural in nature.
- Associative module memory: Association is linking two events that occur close together. Memory researchers explain that people, associate different pieces of information together when they remember certain things. The associative module of memory suggests that memory consists of the mental representation of clusters of interconnected information.