Initial research – basics in memory.
In its very simplest term memory is the ability to store, retain, and retrieve information all kinds of information. There are several ways to classify memories, but they are based on duration, nature and retrieval of information. From an information processing perspective there are three main stages in the retrieval of memory.
Encoding or registration - the process of receiving, processing and combining of
received information to make it memorable.
Storage – creating a permanent record of the now encoded information/memory
Retrieval or recall - the ability to recall the now stored information in response to some
cue for use in a process or activity
The three main classifications of memory
The basic accepted classification of memory is based on the duration of the storage of any memory. I states that there are three distinct types of memory, they are sensory memory, short term memory and long term memory.
Sensory memory – Sensory memory is the memory we create in the initial 200 – 500 milliseconds after an item is perceived. This is the ability to look at an item, and remember what it looked like with just a second of observation. It has been known that people often say they seem to “see” more than they can actually report or recall about a sensory memories. A man named George Sperling was one of the first people to conduct experiments exploring this form of sensory memory. He conducted an experiment known as the “partial report paradigm.” His subjects were presented with a grid of 12 letters, arranged into three rows of 4. His subjects where aloud a few seconds to view the letter and where then asked to remember as many as they could. Based on these partial report experiments, Sperling was able to show that the capacity of the average persons sensory memory was approximately 12 items. but maybe more interestingly that it diteriorated very quickly with in a few seconds he also found that it could not be prolonged.
Short-term memory – Some of the information in sensory memory can also be transferred to short-term memory. Short-term memory allows a person to remember and recall information from several seconds to as long as a minute without rehearsal. Its capacity is also very limited modern estimates of the capacity of short-term memory are lower, typically estimated to be around 4-5 items. But it was found that memory capacity can be increased through a process called “chunking”. For example, if presented with the string of continues number or letters the average person would be able to remember only a few for a short time but if that string where to be cut up and the numbers or letters grouped in smaller chunks people can remember a great deal more. This is because they are able to chunk the information into meaningful groups of letters or numbers. It was found that the ideal size for chunking letters and numbers, meaningful or not, was three.
Short-term memory is believed to rely mostly on an acoustic code for storing information, and to a lesser extent a visual code. It was found that test subjects had more difficulty recalling collections of words that were acoustically similar (e.g. dog, hog, fog, bog, log).
Long-term memory -The storage in sensory memory and short-term memory generally have a strictly limited capacity and duration, which means that information is available for a certain period of time, but is not retained permanently. long-term memory can store much larger quantities of information for potentially unlimited duration. For example, given a random seven-digit number, we may remember it for only a few seconds before forgetting, suggesting it was stored in our short-term memory. On the other hand, we can remember telephone numbers for many years through repetition; this information is said to be stored in long-term memory. While short-term memory encodes information acoustically, long-term memory encodes it semantically. Baddeley discovered that after 20 minutes, test subjects had the least difficulty recalling a collection of words that had similar meanings (e.g. big, large, great, huge).One of the primary functions of sleep is improving consolidation of information, as it can be shown that memory depends on getting sufficient sleep between training and test.
Memory Models
Multi-store the Atkinson-Shiffrin model – The multi-store model was first recognized in 1968 by Atkinson and Shiffrin.The multi-store model has been criticized for being too simplistic. For instance, long-term memory is believed to be actually made up of multiple subcomponents, such as episodic and procedural memory. It also proposes that rehearsal is the only mechanism by which information eventually reaches long-term storage, but evidence shows us capable of remembering things without rehearsal.
The working memory model – In 1974 Baddeley and Hitch proposed a working memory model which replaced the concept of general short term memory with specific, active components. In this model, working memory consists of three basic stores: the central executive, the phonological loop and the visuo-spatial sketchpad. In 2000 this model was expanded with the multimodal episodic buffer. The central executive essentially acts as attention. It channels information to the three component processes: the phonological loop, the visuo-spatial sketchpad, and the episodic buffer.
The phonological loop stores auditory information by silently rehearsing sounds or words in a continuous loop; the articulatory process (the “inner voice”) continuously “speaks” the words to the phonological store (the “inner ear”). The phonological loop has a very limited capacity, which is demonstrated by the fact that it is easier to remember a list of short words (e.g. dog, wish, love) than a list of long words (e.g. association, systematic, confabulate) because short words fit better in the loop. However, if the test subject is given a task that ties up the articulatory process (saying “the, the, the” over and over again), then a list of short words is no easier to remember.
The visuo-spatial sketchpad stores visual and spatial information. It is engaged when performing spatial tasks (such as judging distances) or visual ones (such as counting the windows on a house or imagining images).
The episodic buffer is dedicated to linking information across domains to form integrated units of visual, spatial, and verbal information and chronological ordering (e.g., the memory of a story or a movie scene). The episodic buffer is also assumed to have links to long-term memory and semantical meaning.
The working memory model explains many practical observations, such as why it is easier to do two different tasks (one verbal and one visual) than two similar tasks (e.g., two visual), and the aforementioned word-length effect. However, the concept of a central executive as noted here has been criticized as inadequate and vague.
Other memory experiments
Organization – in 1967 Mandler gave participants of his experiment a pack of word cards and asked them to sort them into any number of piles using any system of categorization they liked. When they were later asked to recall as many of the words as they could, those who used more categories remembered more words. This study suggested that the act of organizing information makes it more memorable.
Distinctiveness – in 1980 Eysenck and Eysenck asked participants of their experiemtn to say words in a distinctive way, e.g. spell the words out loud. Such participants recalled the words better than those who simply read them off a list.
Effort – in the late 70’s Tyler et al had participants solve a series of anagrams, some easy (FAHTER) and some difficult (HREFAT). The participants recalled the difficult anagrams better, presumably because they put more effort into them.
Elaboration – Palmere et al gave his subjects descriptive paragraphs of a fictitious African nation. There were some short paragraphs and some with extra sentences elaborating the main idea. Recall was higher for the ideas in the elaborated paragraphs.
