The Complexity of Human Memory


By Georgia Kitchener


What are memories? How do we manage to maintain memories vividly from years ago? How do all of these memories seem to “fit” and be stored?


Psychologists are keen to find answers to questions like these and have proposed memory models, such as the Multi-Store Model of Memory and the Working Memory Model, to try and illustrate the process of absorbing and retaining information.


The Multi-Store Model by Atkinson and Shiffrin (1968) shows how information is processed into different types of memory. The model of memory consists of three memory stores: the sensory memory (register), the short-term memory (STM) and the long-term memory (LTM).


Information is passed through the different stores through rehearsal, both maintenance and elaborative. Information could not be maintained and developed into long-term memory without this rehearsal. To access memories in both the long- and short-term memory, retrieval is used.
The sensory memory or sensory register (SM) is the initial contact for the external environmental stimuli. It only keeps information for a short amount of time, ¼-½ of a second. The short-term memory (STM) is the information that we are currently aware of and can transition from sensory memory; it can be kept in the short-term memory for longer through rehearsal. Research shows that the duration of the short-term memory is from 18-30 seconds and that it can hold 7 words or letters at a time, but which can remain in the long-term memory, after rehearsal, for a lifetime.


The long-term memory stores information that is largely outside of consciousness but is recalled and retrieved into the short-term memory when it needs to be accessed. Studies by Tulvig, a well-known psychologist and cognitive neuroscientist, show that there are three stores inside the long-term memory. The first stores episodic memory which is memories of events or episodes that have happened to you in your life; this type of memory is time-stamped like a diary and can be quickly and easily accessed with conscious effort. The next store is the semantic memory which stores memory with meaning behind it such as our knowledge of the world; semantic memory is always being added to. Procedural memory is the third store of memory and consists of skills and actions.


Coding is a vital aspect to successful memory and is the way that information is processed. The sensory memory is coded visually and through auditory memory, the short-term memory is coded acoustically and the long-term memory is coded semantically.


In 1974 Baddeley and Hitch argued that the Multi-Store Model was not a full enough explanation of the short-term memory. Arguably, the short-term memory is much more complex,  with memory being an active process with different systems for different types of information.


The central executive allocates information to the different slave systems (the phonological loop and the visual-spatial sketchpad). The model also includes the Episodic Buffer, which temporarily stores the information and can record time sequencing. The phonological loop interprets auditory and written information. There are two subsystems in the phonological loop. The first is the articulatory control system, referred to as the ‘inner voice’, which is used to rehearse verbal information; the second is the phonological store, which is also known as the ‘inner ear’ and which holds speech and spoken words. The second slave system, the visuo-spatial sketchpad, stores and manipulates visual information. It has two subsystems (the visual cache and the inner scribe). The visual cache interprets colour and from and the inner scribe shows spatial relationships between things and objects this includes height and extension.

From these models we can gain a picture of what our memory mapped out may look like, but as time moves on we learn more and more through developments in science and brain scan equipment. I highly doubt these will be the last significant memory models we will see.