Atkinson–Shiffrin memory model
[12] For this reason Atkinson and Shiffrin also called the registers "buffers", as they prevent immense amounts of information from overwhelming higher-level cognitive processes.
[1] While it is generally agreed that there is a sensory register for each sense, most of the research in the area has focused on the visual and auditory systems.
The original evidence suggesting sensory stores which are separate to short-term and long-term memory was experimentally demonstrated for the visual system using a tachistoscope.
That is, as long as a stimulus has entered the field of vision there is no limit to the amount of visual information iconic memory can hold at any one time.
It has been argued that the momentary mental freezing of visual input allows for the selection of specific aspects which should be passed on for further memory processing.
[13] Echoic memory, coined by Ulric Neisser,[15] refers to information that is registered by the auditory system.
[21] Fortunately, the information can be held in the short-term store for much longer through what Atkinson and Shiffrin called rehearsal.
[22] These chunks, which were noted by Miller in his seminal paper The Magical Number Seven, Plus or Minus Two, are defined as independent items of information.
Atkinson and Shiffrin cite evidence for this transfer mechanism in studies by Hebb (1961)[23] and Melton (1963)[24] which show that repeated rote repetition enhances long-term memory.
One may also think to the original Ebbinghaus memory experiments showing that forgetting increases for items which are studied fewer times.
[24][26] Atkinson and Shiffrin cite hippocampal lesion studies as compelling evidence for a separation of the two stores.
[27] One may also be familiar with similar evidence found through the study of Henry Molaison, famously known as H.M., who underwent a severe bilateral medial temporal lobectomy which removed most of his hippocampal regions.
One of the early and central criticisms to the Atkinson–Shiffrin model was the inclusion of the sensory registers as part of memory.
[28][29][30] Baddeley and Hitch have in turn called into question the specific structure of the short-term store, proposing that it is subdivided into multiple components.
The model has been further criticized as suggesting that rehearsal is the key process that initiates and facilitates transfer of information into LTM.
In this framework, items which are encoded at a deeper, more semantic level are shown to have stronger traces in long-term memory.
[33] A short (non-inclusive) example comes from the study of Henry Molaison (H.M.): learning a simple motor task (tracing a star pattern in a mirror), which involves implicit and procedural long-term storage, is unaffected by bilateral lesioning of the hippocampal regions while other forms of long-term memory, like vocabulary learning (semantic) and memories for events, are severely impaired.
Context information refers to the situational and temporal factors present at the time when an item is in the short-term store, such as emotional feelings or environmental details.
On the other hand, the strength of the item-item associations is proportional to the amount of time that two items simultaneously existed in the short-term store.
The recency effect occurs because items at the end of the test list are likely to still be present in short-term store and therefore retrieved first.
Since a distracting task after the presentation of word pairs or large interpresentation intervals filled with distractors would be expected to displace the last few studied items from the short-term store, recency effects are still observed.
[38] Additionally, the original model assumes that the only significant associations between items are those formed during the study portion of an experiment.
The extension proposes a store for preexisting semantic associations; a contextual drift mechanism allowing for decontextualisation of knowledge, e.g. if you first learned a banana was a fruit because you put it in the same class as apple, you do not always have to think of apples to know bananas are fruits; a memory search mechanism that uses both episodic and semantic associations, as opposed to a unitary mechanism; and a large lexicon including both words from prior lists and unpresented words.
