Human Memory Layers

Oddly enough, humans have layers of memory as well. The layers do not correspond directly to the layers in computer memory but there are 3 of them.

1. Sensory Store

The sensory store is the first layer of human memory and is a nearly perfect record of any and all sensory stimuli for about the last 30 seconds. Most notable in the research of sensory memory was Sperling, who used a T-Scope device to flash sets of images up for 1/2 second intervals, then test his subjects on their memory of them. It was through this procedure that it was found that while the sensory store does store items almost perfectly, recalling those stored stimuli is difficult for humans and on average we can only recall 3 1/2 images or objects from a set. If, however, the images are subdivided into sets and those sets given key phrases or sounds, a human can recall any of the sets, provided each set is under or around 4 objects.

2. Short Term Store

The short term store lasts for about 20 seconds and is an auditory store, meaning we store information their as sound, or talking to ourselves. Keeping an object in short term can be achieved by constant internal repetition, or rote rehearsal. Most notable in this work was a man named Miller, who found we can store 7 objects or concepts in short term store. Miller was a phone company employee and it is thus that up until recently phone numbers contained only 7 digits, the number we could remember long enough to jot down or dial.

A note before continuing: both sensory and short term store have time limits on them, and without processing the information and giving it some kind of meaning, after the memory is faded from sensory and short term stores it is gone forever.

3. Long Term Store

If we have taken in information we can transfer memory from either sensory or short term store to the long term store. Some interesting aspects of long term store are that all information there is stored semantically, or by meaning. Long term store has no known time limit and no known quantity, ergo we could store a limitless amount of information indefinitely if we could process all information into meaning. You may wonder why, if long term store is permanent, can we forget things we knew for a long time. The answer is that the memory persists, but the cues to recall it are gone. Much like finding a specific passage in a book, unless the place is marked, or has cues associated, finding the place in the book could be very difficult in even a small book, and next to impossible in an encyclopedic tome like the brain.


1. Sensory Store: 30 seconds of physical memory, recalling on average 3 1/2 items from a set.

2. Short Term Store: 20 seconds of auditory memory, recalling on average 7 items.

3. Long Term Store: Limitless time and quantity, but dependent on meaning and the ability to find the memory.

You might also look into the Method of Loci as a means of improving memory. Might be my next node, I dunno.