Memory Has Been Separated Into Three Categories

Memory has been separated into three categories on the basis of the "amount of time the memory lasts." (Zhang, 2004, p.1) The three categories are stated to include the following: (1) sensory memory; (2) short-term memory; and (3) long-term memory. (Zhang, 2004, p.1) The focus of this brief study is to describe each of these memory storage processes.

Sensory Memory & Short-Term Memory

Sensory memory is reported to act as "a buffer for stimuli received from the senses. A sensory memory exists for each sensory channel." (Zhang, 2004, p.1) Sensory memory is the shortest-lived of all types of memory and lasts only milliseconds to a few seconds. (Zhang, 2004, paraphrased) Iconic store is where visual images within sensory memory are stored for only a very short period and serves to integrate our visual experience. It is reported that in a presentation of three rows of four letters to subjects for 50 milliseconds that Sperling (1960) found that they were able to report four or five letters, but were aware that there were many more. (Zhang, 2004,, paraphrased)

Sperling discovered that this type of visual memory only lasted about one-half a second. Echoic store is where auditory senses are retained in sensory member for a short time. The estimation stated for the duration of echoic memory is approximately 250 milliseconds to one-half a second. Finally, the haptic store in sensory memory is reported to retain the physical senses including touch and internal muscle tensions. Zhang (2004) states that incoming memory is first held in sensory memory and through attention the information is then passed to working memory where it is processed.

II. Short-Term (Working) Memory

Short-Term Memory involves selective attention determining what information moves from sensory memory to short-term memory, which is often stored as "sounds, especially in recalling words, but may be stored as images." (Clark, nd, p.1) Short-term memory is reported to work basically the same way as the computer RAM (Random Access Memory) because it "provides a working space for short computations and then transfers it to other parts of the memory system or discards it. It is thought to be about seven bits in length.." Or otherwise stated, the individual generally remembers seven items. STM is reported to be "vulnerable to interruption or interference." (Clark, nd, p.1) Short-term memory can retains items indefinitely through use of rehearsal or repeating the information repeatedly. Working memory and short-term memory are held by some to be one in the same however, those who conduct memory research are reported to "often consider this a specialized term referring for information about the current task.

III. Long-Term Memory

Long-term memory is any memory that has been retained for years or longer and is inclusive of all the individual's information about the world stated to include both "semantic and factual information" in addition to autobiographic experience. (Rutger's University Memory Disorders Project, 2011, p.1) The organization of long-term memory is such that it is not difficult to reach a stored item and this can be accomplished through various routes. The example stated is as follows:

" the concept "umbrella" may be retrieved by seeing an umbrella, experiencing a rainstorm, hearing the words to the song "Let a smile be your umbrella," and so on. Retrieval of an item also facilitates other related items: so that retrieving information about a cat can lead to retrieval of information about dogs, lions, specific instances of cats (Grandmother's tabby), the Cheshire Cat from Alice in Wonderland, and so on." (Rutger's University Memory Disorders Project, 2011, p.1)

Long-term memories are classified in several ways by their content. Declarative memory is a term representing information that is easily accessed for "conscious recollection and verbal retrieval (i.e., it can be "declared")." (Rutger's University Memory Disorders Project, 2011, p.1) Two subclasses of declarative memory are episodic memory, which is autobiographical information, and semantic memory, which is factual information about the world (vocabulary items, knowledge of what a hammer is used for, memory of multiplication tables, etc.)." (Rutger's University Memory Disorders Project, 2011, p.1)