What are the different kinds of Memory System?



There are three kinds of Memory System I. Sensory Memory, II. Short-term Memory and III. Long-term Memory.

I. Sensory Memory

Sensory memory is the initial momentary storage of information lasting: only an instant. Sensory memory, also known as 'sensory buffer' or ‘sense, register' refers to the recorded or transcribed raw physical input. Stimuli from the environment (sights, sounds, smells etc.) constantly bombard our receptors.

Receptors are the body's mechanisms for seeing, hearing, tasting smelling, and feeling. The sensory memory holds all these sensations for a brief period of time until such information are transformed to other memory stores. If the transfer is not virtually instantaneous then the information gets lost.

It is generally accepted that there are as many sensory memories as are sensory registers. But the researchers have mainly focused on the visual (iconic), and auditory (echoic) sensory memories the following are a few important basic characteristics of sensory memory:

(i) The capacity of the sensory memory is very large, (ii) the duration of sensory memory is fragile (short duration), (iii) the content of sensory memory resembles the sensations from the original stimulus, (iv) the visual sensory resister holds information for less than a second and (v) the auditory memory lasts for up to 2 to 4 seconds. if information from the sensory memory does not pass to the short term store, it is lost for good.

II. Short-term Memory

It is the memory system that holds limited amount of information for relatively a short period of time. After the information is processed from the sensory store, and has been recognized and attended, it moves into short-term memory. But the sensory information does not reach the short-term -memory directly; rather it reaches in a coded form.

Once noticed and transformed into patterns of images or sounds, the information in sensory -memory is readily available for further processing. Short-term memory is otherwise known as 'working memory', which is the 'workbench' of the memory system, the component of memory where new information is held temporarily and combined with knowledge from long-term memory.

Unlike sensory memory, working memory is temporary, active and conscious and is like the workspace or screen of a computer- its content is activated information or what you are thinking about at the moment. For this reason, some psychologists consider the working memory to be synonymous with consciousnesses. When you hear the telephone number of your friend, you store it for a short period of time in your STM.

According to Broadbent (1958), STM is interpreted as a bio-electric process in the form of a close neural circuit and is strongly susceptible to forgetting our (filter effect), and interfering influences. Short-term memory is more selective, and more permanent than sensory memory. It is quite possible to retain information in working memory through maintenance rehearsal processes by repeating the information to oneself.

Short-term memory or working memory has certain characteristics. They are:

1. The storage capacity of STM/Working memory is quite limited. Some psychologists argue that working memory is limited not by the number of bits of information it can store, but by the amount of information it can hold in a rehearsal system of about 15 seconds. The STM can hold seven units of information or items plus or minus two, i.e., 7 + 2.

2. Thus, the duration of information, in the working memory lasts for about 15 to 20 seconds. This is why working memory has been called 'short- term memory'. Keele (1973) found from his experimental study that material in STM disappears in 15 to 25 seconds if it is not practiced.

3. The content of information in working memory may be in the form of images or may be structured more abstractly, based on meaning According to Baddeley (1986) and Jurden (1995), there are actually two working memory systems: one for language based information, and another for nonverbal, spatial and visual information.

Craik and Lockhart (1972) viewed that there are two types of rehearsals involved in the process. They are- maintenance rehearsal, which involves repeating the information in one's mind like remembering phone numbers, and elaborative rehearsal, which involves connecting the information by associating it with something else that one has already come across.

For example, suppose you meet a person on the road whose appearance looks like that of your brother. In order to keep him in your memory, one has to make the association of appearance of the brother with the person Rehearsal, thus, plays the role of executive control process that affects the flow of information through the information processing system. So the information from the environment reaches the sensory memory, and after screening, reaches the working memory where it is rehearsed over and over to ourselves, and after enough of such rehearsal, it goes into long-term memory.

Long-term Memory

It is the memory system that stores large amount of information over a long period of time. Long-term memory is the third stage of memory. It is a permanent storehouse of memory having unlimited capacity of storage.

Long- term memory holds the information that is well learned. For example, recalling the telephone numbers of all of your friends is an example of LTM. Thus, long-term memory is the memory system for the retention of large amount of Materials over long period of time. It may be noted that the information enters parking memory very quickly.

To move information into long-term memory requires more time and a bit of effort. But once the information is stored in the long term memory, it remains there permanently for days, weeks, months, years and even a lifetime. In the long-term memory, the information is stored in an organized, categorized and classified manner.

Psychologists suggest that information is stored in long-term memory as either visual images or verbal units or both. Psychologists who agree with this point of view believe that information coded both visually and verbally is easier to learn. Long-term memory represents permanent changes in the brain.

When we think about memory, we generally mean long-term memory. It includes almost anything that you remember which is essential for your self-identity and proper functioning. The long-term memory can be episodic, semantic, or procedural. These three types of long-term memory are discussed later in this chapter.