Stages of Memory

[Ready for Fall 2026]

Modified: 2026-08-03 6:50 PM CDST

• Classically, memory can be thought of as a series of time-based stages.
  • Each succeeding stage contains fewer items than the preceding one.
  • Also, movement of items from one stage to another is accomplished by separate memory processes.

• The sensory store is the first stage.
  • Basically, everything you perceive enters sensory memory but very little remains.
  • Partial report experiments for visual stimuli (iconic memory) have shown that items are retained for two seconds or less.
    • Here, participants can remember any of 16 letters that were flashed in front of them for a fraction of a second if they are asked to report within two seconds.
    • After two seconds they cannot remember any of the letters.
  • Auditory sensory memory (echoic memory) lasts as long as 30 seconds and may reflect the linear nature of speech.
  • Visual data, on the other hand, arrive massively in parallel.
• Short term memory (STM) is the next stage.
• Pure STM lasts around 20 seconds.
• Pure STM occurs when subjects are prevented from rehearsing.
  • One way to prevent rehearsing is to have subjects count backwards from 100 by threes (e.g,. 100, 97, 94, ...) after you show them a word.
  • In real contexts, rehearsal makes STM last longer.
    • Think of the following example.
    • Your car breaks down in an unfamiliar place.
    • You walk to a phone booth, look up Al's Garage, dial the number, it's busy.
    • A minute later you want to call again, but you have to look up the number again.
    • Why? Because you did not rehearse it.
      • If you had said "555-4231" over and over to yourself for that minute, you would not have had to look it up. That is a form of rehearsal.
  • STM is limited in size. George Miller described it as 7 items + or - 2 items.
    • That finding is now referred to as the "magic number 7" for STM.
    • Most people can easily hold 7 items in STM.
    • Notice that telephone numbers have seven places.
      • What do you think is going to happen when telephone numbers get longer?
    • Do you use ZIP + 4, the full ZIP code? It is nine numbers long.
      • Most people refuse to use 9 digit ZIP codes.
      • Do you know yours?
      • Mine is 71753-2511
      • SAU's is 71753-5000.
• Long-term memory (LTM) lasts from minutes to years.
  • Consolidation is the name of the process that puts items into LTM.
    • Little is known of the details of how consolidation works.
  • LTM can also be broken down into parts.
    • Procedural memories are memories about how to perform activities.
      • For example, riding a bicycle.
    • Semantic memories are basically the same as knowledge.
      • For example, 3 X 7 = 21, or knowing the capital of France. or of Burkina Faso (Paris or Ouagadougou respectively)
    • Semantic memories are not time tagged, meaning you cannot usually remember when you learned those items.
    • Episodic memories are personal and are time tagged:
      • the day a relative died,
      • the time the dog bit you,
      • where you met your spouse,
    • Think of them as the episodes of your life.
• Working memory is a newer concept proposed by Baddeley to better describe the workings of short term memory.
• According to Baddeley, working memory includes:
  • the rehearsal loop,
  • the visuospatial sketchpad,
  • and the executive control system.
• The rehearsal loop is essentially the same as the traditional view of STM.
• The visuospatial sketchpad component allows for the handling of images.
• The executive control system is in charge of making decisions based on the limited amounts of information that exist in STM.