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Explain and describe the function, capacity, and duration for each of the three stages of memory: sensory, short-term, and long-term. Choose one reason why people forget, and explain. 

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Sensory memory captures input from our senses and holds on to it for a very short period of time (generally accepted to be less than one second). Basically, sensory memory captures input and immediately discharges it, unless we keep paying attention to that sensory input. Information not payed attention to...

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Sensory memory captures input from our senses and holds on to it for a very short period of time (generally accepted to be less than one second). Basically, sensory memory captures input and immediately discharges it, unless we keep paying attention to that sensory input. Information not payed attention to is not transferred to short-term memory. It is lost. The purpose of sensory memory is a bit like sorting or sifting. It allows the brain to retain the vast input from our senses for just long enough to determine whether it is worth holding on to.

If we do keep paying attention to a stimulus, that information is transferred to short-term memory. Short-term memory, too, is short in duration. It is generally thought to be less than one minute. It is also finite in capacity. It is thought that short-term memory can store about seven items. Here, too, information that is not transferred is lost. Repetition and "chunking" (grouping information together) extends the duration and capacity of short-term information and increases the likelihood that information will be transferred to long-term memory. The purpose of short-term memory is to further winnow the input from our senses. Some information is worth hanging on to for more than a fraction of a second but does not need to be stored long-term.

The third stage of memory, long-term memory, is long in duration, possibly even permanent. If a memory makes it past sensory and short-term memory, it will be stored in long-term memory. Information can still be lost from long-term memory by not "using" or reaccessing the memory, but information that is used and reaccessed frequently can be stored in long-term memory potentially forever. The purpose of long-term memory is to store information that has continuing or ongoing usefulness. Long-term memory allows for many of the higher-level functions of the brain: learning from experience, comparing the present to the past, deciding from experience on a course of action in the present, and so on.

Throughout the stages of memory, information can be "forgotten" by lack of use (lack of access and repetition). Information that is not "used" by the brain in sensory memory is forgotten. Information that is not used in the duration of short-term memory is forgotten. Information that makes it to long-term storage but is not reaccessed frequently can also be lost. For example, you might remember the procedure for making a chocolate cake for as long as you continue making chocolate cakes. If you quit your job as a baker and become an accountant, the procedure for making chocolate cakes can be lost.

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Short-Term Memory (STM) is a memory system where information is briefly held while it is being used; as a result, it is sometimes called working memory.  According to research conducted by George Miller (1956), short-term memory is able to contain approximately seven items or pieces of information at a time and can hold these pieces of information for around 12-30 seconds on average.

Long-Term Memory (LTM) is a memory system where information is placed for long-term or permanent storage.  Long-term memory capacity is virtually limitless; the problem is finding a way to actually retrieve the information from memory.  Without the right retrieval cues, information can be stored in long-term memory, but never be accessed.  Most researchers agree that information stored in LTM is there permanently--all it takes to access that information is the right cues.

Sensory Memory is essentially the first stage in the memory process; it is the point where information enters the nervous system through various sensory systems (sight, taste, sound, etc.).  Information that has been encoded into sensory memory takes the form of neural messages that travel through the nervous system.  The memory is accessible as long as the neural message is still moving through the nervous system to be further processed in the brain.

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