Memory Part 1: Echoic and Iconic

Today, I’m just going to jot down a few things I’ve begun to learn as I’ve heard the first few lectures in a new Great Course.  The course is on Memory (Memory and the Human Lifespan), which is a subject I find fascinating.  This fascination stems from my ongoing study of the subject of knowledge.  I think most of us would agree that memory is intimately involved in knowledge – how can you claim to “know” something if you can’t also claim to “remember” it, in some sense.  Yet, memory can be so amazingly flawed, even in people with “normal" memory.

Anyway, here are a few tidbits:

“Memory” is not one single thing.  It is a set of processes which go on in our brains, which allow past experiences to affect our current or future behavior.  And though many of us think of there being just “short-term” memory and “long-term” memory, it’s more complicated than that.  In fact, there are two easily recognized kinds of memory which are even “shorter-term” than what we call “short-term” memory.  They are both types of sensory memory.

Echoic Memory – This is something I never thought about, but it’s clearly something which exists.  “Echoic” comes from “echo” and as you might guess, it relates to auditory memory, or the memory of what our ears have heard.  But it’s not long-term, such as remembering the song you heard at a concert.  Echoic memory stores, for a very short time, the information which your auditory system took in while you were concentrating on something else.  As Dr. Steve Joordens explains, we often have the experience that someone begins talking to us when we are focused on something else, and our immediate reaction is to say “What?” Often, the person then begins to repeat the question, but before they can, we realize that we actually did hear what they said.  But, in fact, we did not “consciously” hear it when the speaker first spoke.  Instead, the information was stored, for a brief time, in our Echoic Memory, which “plays it back” for us.  I expect many of you recognize this same effect. 

For me, personally, it seems related to another behavior I have.  I’ll be sitting in my living room, next to my wife, but paying attention to my computer (probably a game.)  I will then say something and Sherry will say “I just said that.”  I don’t remember, at all, hearing her.  But I believe her.  And now I know how it could happen.  The words she said went into my Echoic memory, but they stayed there, unattended to, for too long.  Yet, they somehow reached a sub-conscious part of my mind.  I can't be sure that this is truly a function of Echoic Memory -- this specific topic did not come up in the lessons I have heard -- but it seems to fit.

Iconic Memory – Like Echoic Memory, which is related to the sense of hearing, Iconic Memory is related to the sense of sight.  This type of memory is even shorter-term than Echoic.  The easiest way to realize that you have this type of memory is to think of watching a light source in a dark place.  Personally, I think about watching sparklers on the fourth of July – imagine it, if you can.  A kid waves a sparkler in the darkness, and you seem to see a streamer of light following behind the sparkler.  The same thing can happen with any other light source while it’s moving.  We know, physically, that the light source is in only one position at any moment, but we “see” a residual image of the light as it moves.  That is a function of Iconic Memory. 

It turns out Iconic Memory is also in constant use when we are living normal lives.  The perception we have of one seamless view from our eyes is really built from the combination of hundreds of little pieces of Iconic Memory.  Our eyes, we learn, are very rarely holding themselves in one position for very long at all.  They are making tiny little movements, capturing the scene in front of us, helping us build a more complete scene.  

 It’s fascinating.

I've also heard about Episodic Memory, and was just listening to two lectures on Working Memory.  More on those another time.  Additionally, the course is teaching techniques for "Improving" memory, though really it's more about understanding how memory works, so you can to put the right kinds of effort into getting things to be more easily retrieved from your memory.

I bet I will listen to this course more than once.  But I am also pretty certain to write more about what I have learned before the course is over, because, as it turns out, writing about what I've learned helps make it more likely that I can retrieve it in the future.  Which is, after all, one thing I really want!

Oh, and one other thing about this course: it describes some of the seminal experiments which were used in the study of memory, and so far most of them have been very easy to understand and would be quite easily duplicated, in one were so inclined.

Fascinating, I tell you.