Sensory, Short term and Long term memory

      The stage theory of memory has been a very influential theory in cognitive psychology. This theory is often used to explain the basic structure and function of memory. Initially presented in 1968 by Atkinson and Shiffrin, this theory outlines three separate stages of memory: sensory memory, short term memory and long term memory. We should keep in mind that Atkinson and Shiffrin themselves did not suggest that this distinction in memory is not physiological but rather a hypothetical construct. This distinction is not directly absolvable but it serves as a mental model to understand how a psychological phenomena works.

      I.Sensory memory

      Sensory memory is the earliest stage in memory, in this stage sensory information are stored for a very brief period of time. And here we can talk about iconic storage, or iconic memory which is a sensory registration that holds visual information for a brief period, and echoic memory which holds auditory information for a brief period.

 II.Short term memory

      We usually do not have any conscious access to our sensory memory, but short term memory represents information that we are currently aware of or thinking about. So sensory information get in our sensory memory however they only stay for few seconds after that information that were selected due to selective attention get in short term memory. In general our short term memory capacity is about seven items plus or minus two according to a study made by Miller in 1956. Normally information is held in short term memory approximately 30 seconds. However information can stay longer due to maintenance rehearsal which refers to repeating the information over and over. According to Atkinson and shiffrin short term memory does not only hold few items it also has some process that regulates the flow of information to long term memory. An example of that is elaborative rehearsal which refers to organizing the information and associating it with information already existing in long term memory.

III.Long term memory

        Long term memory refers to the continuing storage of information. This information is largely outside of our awareness, but can be called to be used when needed. Some of the information is fairly easy to recall, while others are much more difficult to access. The storage capacity can be answered quickly because the answer is simple “we do not know”. Some theorists have suggested that the capacity of long term memory is infinite like Bahrick and Hall.

        We can also talk about two types of long term memory: declarative or explicit memory which is responsible of remembering explicit information and here we can also find two types: semantic memory which is responsible of remembering general knowledge, and episodic memory which is responsible of remembering particular events you have personally experienced. On the other hand we can find nondeclarative or implicit memory and according to Squire this memory comprises procedural memory, priming effects, simple classical conditioning and nonassociative learning. Learn more explicit vs implicit memory. learn more.


  • Atkinson, R. C, & Shiffrin, R. M. (1971). The control of short-term memory. Scientific American, 225, 82-90.

  • Miller, G. A (1956). The magical number seven, plus or minus two: some limits on our capacity for processing information. Psychological Review, 63, 81-97.

  • Robert J. Sternberg (2008). Cognitive Psychology, Fifth Edition.

See Also:

Cognitive Revolution

Ebbinghaus' experiment of memory

encoding storage and retrieval

Working memory

Explicit vs implicit memory

the levels of processing model

The process of forgeting

the seven sins of memory