Box 1: Sensory Memory (abbreviated SM)-- a very brief, exact copy (a trace) of what you just sensed

Imagine that you are looking at the television, but not paying attention to the program because you are talking to a friend. Suddenly, your friend points to the television set. Thanks to your sensory memory, you can hit a rewind button in your mind that allows you to replay the last little bit of the program.
If you replay the audio from the program, you are using your echoic memory: the sensory memory for hearing that allows you to, in a sense, hear an echo of what just happened. 
  Being able to use your echoic memory to replay the last 3-5 seconds of what your ears just sensed, allows you to

• Know whether a sound is coming from your right or your left because your echoic memory helps you figure out whether the sound hit your left ear or right ear first. You are so good at figuring out where sounds come from that you can learn to "see" with your ears--a little like a bat does!
• Effortlessly keep all the sounds of an entire word together. (If you don't believe me about how effortlessly you do this or you just want to see what a pain it is to understand spoken words without echoic memory, click the first link below--but remember, I did warn you! Then, to appreciate how effortless understanding speech is with echoic memory, click the second link below. After that, you will probably want to thank your echoic memory.)
  1. When speech is artificially slowed down so much that you can't use echoic memory to keep the sounds together, you can still understand words, but you will probably find the effort to understand the words both exhausting and unpleasant (demo#1).
  2. With speech presented at a normal rate, you can use echoic memory, so keeping the sounds together is much easier. (demo #2)
• Replay words or phrases that you initially misheard (e.g., you may have misheard "plan it" as "planet" or euthanasia" as "youth in Asia").
• Act like you were listening when you weren't. For example, suppose a teacher believes you were not listening. Although you weren't listening, you say you were.  The teacher responds by asking, "Well, then, what did I say?" You may have used your echoic memory to repeat the last few words of what the teacher said even though you weren't listening. Two practical implications:
  1. The next time someone says "what?" or "huh?" right after you said something, rather than repeating yourself, you could simply make them use their echoic memory to hear an "echo" of what you just said. 
  2. If your "listener" keeps repeating the last few words of your sentences, do not assume they are really listening to what you are saying.

If you replay the image that was on the television screen, you are using your visual sensory memory (typically called iconic memory). Iconic memory is, in a sense, a picture drawn in rapidly disappearing ink. See a very short (less than a second) demonstration of how quickly information decays from iconic memory Because pictures in  iconic memory are copies of what you just saw, are "drawn" automatically, and usually fade in less than half a second, it wasn't until

• 1740 when a scientist discovered iconic memory (the first 20 seconds of this youTube video resembles a re-enactment of that discovery). Iconic memory (sometimes called "persistence of vision") is usually easy to overlook because it is (1) an exact copy of what you saw, (2) automatic, and (3) fleeting.
• 1960 when a scientist discovered that sensory memory could hold more than a few items. Click on one of the links below to find out more about how that scientist--George Sperling--figured out that sensory memory was large but short.
• our one-minute animation explaining how George Sperling's classic, clever experiment showed how large iconic memory really was
• a video discussing George Sperling's experiment (with audio)
• short (1 paragraph) description of George Sperling's experiment
• Today (probably) when you realized that if you watch a 2-hour (non-digital) movie in a movie theater, you are looking at a blank, dark screen for 1 hour (explanation).

A note about iconic memory's role in seeing movies:

    If slides are projected on a screen at a rate of 12 slides or more per second,  the slide on the screen stays in your iconic memory during the gap between slides. Because you are "seeing" the memory of the previous slide instead of the gap between the slides, you see "moving pictures" (i.e., "movies" or "motion pictures"). 
    If, on the other hand, slides are projected at a rate slower than 12 a second, the previous image is gone from iconic memory before you see the next image. Because you are not seeing a memory of the previous slide and are instead seeing the gaps between each slide, you see a slide show rather than a movie.

 Iconic memory does not seem to be related to what we consider intelligence:

• Some people have relatively long iconic memories (these people are called "eidetikers"). Their "photographic memory" can hold an image for seconds or even minutes. However, their superior iconic memory seems to be a worthless superpower: Most people who have it tend to be young children--and those children usually outgrow it. In addition, college students who are eidetikers seem to get, if anything, lower grades than other college students.
• Chimps do not do well on human tests of intelligence. However, young chimps have better iconic memories than we do. See chimps demonstrate their amazing iconic memory (Although many press reports credited the chimps' impressive performances to "short-term memory," the chimps' impressive performances were probably due to having impressively long iconic memories. That is, young chimps, like some young human children, seem to be eidetikers.)

Getting information from Sensory Memory to Short Term Memory

Short Term Memory

Back to the 3 Box Model

Back to Memory Menu

Back to Lecture Menu

Copyright 2020-2023 Mark L. Mitchell