This model of memory remained under extensive research in the following years.
The physical growth in size of cerebrum and the number of functions associated with this evolved cerebrum demonstrates an important step in the evolutionary ladder of natural life. Memory is one of the very complicated functions of complex life forms and this complexity reaches its maximum when Homo sapiens are analyzed. Atkinson-Shiffrin model of memory is an attempt to explain the various processes of memory which continue to operate in our brains.
The first level of memory is identified as sensory memory. No matter which kind of stimulus is applied to the various senses of the body, the form of information that is delivered to the central nervous system is in the form of electrical impulse or the so called ‘nerve impulse’. For the purpose of translation of external stimuli, a number of receptors are present in the body, that continuously receive impulses in the form of vibration, sound, pressure, light and so on. These impulses are translated into electrical nerve impulses by their respective receptors and are then delivered to the brain as electrical signals. This sensory memory has a very short life span and it persists for only a few seconds i.e 2-3 seconds.
The stage between sensory memory and long term memory is called short term memory. Certain chunks of information from sensory memory are shifted to short term memory which is also called working memory because the information stored there needs further processing. Short term memory easily fades away as soon as attention is drawn to any other matter; it lasts for only 18 to 20 seconds unless the information is rehearsed. Any information that is not lost after 18 to 20 seconds is transferred to long term memory.
The capacity of short-term memory is limited and it is for this reason that only a small amount of information can be retained in short-term memory