Types of Memory: Sensory Memory, Short-term Memory (STM) or “Working Memory”, Long-term Memory (LTM)
Have you ever drawn in the dark bright lines or figures by moving fast, in the air, a sparkler? Most probably you will give a positive answer, but you will be actually lying. Lines of light, drawn with sparklers, do not exist. You could see figures and lines, but you “saw” them with the help of your memory, because the image of the light of a sparkler remained in your memory and making you see the lines left by in the dark.
This kind of memory is called sensory memory and works a photographic memory which lasts for very short time: milliseconds, up to a second. The information provided by the sensory memory is not processed, but simply filtered based on specific physical properties of stimuli and transferred to the short term memory. The attention control is the one selecting an active specific nerve pathway, which passes the information to the Working Memory.
Short Term Memory (STM)
Using the Short Term Memory (STM) or the Working Memory (WM) the information is retained for a rather short period of time (15–30 seconds). The capacity of the Short Term Memory is five to nine pieces of information. “Pieces of information” or chunk means single digits or letters, whole words or sentences. Chunking the information helps to memorize more than just single items in the common sense.
The Working Memory is a form of Short Term which interferes in dealing with two different tasks simultaneously. It consists of three parts: phonological loop, visuospatial sketch pad and central executive.
The Phonological Loop seems to be a system specialized for language and it helps retaining information such as phone numbers, people’s names or general understanding of what other people are talking about. With the Phonological Loop, the storage of information lasts two seconds if it is not rehearsed explicitly. The repetition of information deepens the memory.
In the Visuospatial SketchPad stores the information about the position and properties of objects can be stored. The component that connects the Phonological Loop and the Visuospatial SketchPad is the Central Executive, which combines both kinds of information, the verbal and the visual information.
The Central Executive also links the Working Memory to Long Term Memory, controls the storage in Long Term Memory and the retrieval from it. The storage is influenced by the duration of holding information in Working Memory and the amount of manipulation of the information. The information is stored for a longer time if it is semantically interpreted and viewed with relation to other information already stored in Long Term Memory. This is called Deep Processing.
Long Term Memory
This form of Memory stores memories for a longer time, from a few minutes to several or for a lifetime. Long Term Memory is divided in Declarative (conscious) and Implicit (unconscious) Memory. The Declarative Memory may be Episodic and Semantic Memory, while the Implicit Memory may be Priming Effects Memory and Procedural Memory.
The Episodic Memory deals with the personal memories- autobiographical information. Typically, those memories are connected to specific times and places.
Semantic Memory is not connected to personal events. It refers to the general knowledge about the world. Vocabularies, concepts, numbers, facts or typical ways on how typical situations can evolve are stored in the Semantic Memory. Semantic and Episodic Memory can enhance one another.
Priming Effect interferes in implicit learning (learning without being conscious of it). Priming is an implicit memory effect in which exposure to a stimulus influences a response to a later stimulus.
Procedural Memory is responsible for highly skilled activities that can be performed without much conscious effort (example: tying of shoelaces or the driving of a car).
In theory, the capacity of Long Term Memory is infinite, but it was not established without doubts if the information is stored in the Long Term Memory forever or whether information can get deleted. It is not known if the information that cannot be recalled is not accessible or it is deleted. Concerning this subject, there are several theories about the “forgetting” of information.
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- Baddeley, A. D. (1986). Working Memory. Oxford: Oxford University Press.
- Atkinson, R. C. & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes.