I recently reported on a finding that memories are stronger when the pattern of brain activity is more closely matched on each repetition, a finding that might appear to challenge the long-standing belief that it’s better to learn in different contexts. Because these two theories are very important for effective learning and remembering, I want to talk more about this question of encoding variability, and how both theories can be true.
First of all, let’s quickly recap the relevant basic principles of learning and memory (I discuss these in much more detail in my books The Memory Key, now out-of-print but available from my store as a digital download, and its revised version Perfect Memory Training
network principle: memory consists of links between associated codes
domino principle: the activation of one code triggers connected codes
recency effect: a recently retrieved code will be more easily found
priming effect: a code will be more easily found if linked codes have just been retrieved
frequency (or repetition) effect: the more often a code has been retrieved, the easier it becomes to find
spacing effect: repetition is more effective if repetitions are separated from each other by other pieces of information, with increasing advantage at greater intervals.
matching effect: a code will be more easily found the more the retrieval cue matches the code
context effect: a code will be more easily found if the encoding and retrieval contexts match
Memory is about two processes: encoding (the way you shape the memory when you put it in your database, which includes the connections you make with other memory codes already there) and retrieving (how easy it is to find in your database). So making a ‘good’ memory (one that is easily retrieved) is about forming a code that has easily activated connections.
The recency and priming effects remind us that it’s much easier to follow a memory trace (by which I mean the path to it as well as the code itself) that has been activated recently, but that’s not a durable strength. Making a memory trace more enduringly stronger requires repetition (the frequency effect). This is about neurobiology: every time neurons fire in a particular sequence, it makes it a little easier for it to fire in that way again.
Now the spacing effect (which is well-attested in the research) seems at odds with this most recent finding, but clearly the finding is experimental evidence of the matching and context effects. Context at the time of encoding affects the memory trace in two ways, one direct and one indirect. It may be encoded with the information, thus providing additional retrieval cues, and it may influence the meaning placed on the information, thus affecting the code itself.
It is therefore not at all surprising that the closer the contexts, the closer the match between what was encoded and what you’re looking for, the more likely you are to remember. The thing to remember is that the spacing effect does not say that it makes the memory trace stronger. In fact, most of the benefit of spacing occurs with as little as two intervening items between repetitions — probably because you’re not going to benefit from repeating a pattern of activation if you don’t give the neurons time to reset themselves.
But repeating the information at increasing intervals does produce better learning, measured by your ability to easily retrieve the information after a long period of time (see my article on …), and it does this (it is thought) not because the memory trace is stronger, but because the variations in context have given you more paths to the code.
This is the important thing about retrieving: it’s not simply about having a strong path to the memory. It’s about getting to that memory any way you can.
Let’s put it this way. You’re at the edge of a jungle. From where you stand, you can see several paths into the dense undergrowth. Some of the paths are well-beaten down; others are not. Some paths are closer to you; others are not. So which path do you choose? The most heavily trodden? Or the closest?
If the closest is the most heavily trodden, then the choice is easy. But if it’s not, you have to weigh up the quality of the paths against their distance from you. You may or may not choose correctly.
I hope the analogy is clear. The strength of the memory trace is the width and smoothness of the path. The distance from you reflects the degree to which the retrieval context (where you are now) matches the encoding context (where you were when you first input the information). If they match exactly, the path will be right there at your feet, and you won’t even bother looking around at the other options. But the more time has passed since you encoded the information, the less chance there is that the contexts will match. However, if you have many different paths that lead to the same information, your chances of being close to one of them obviously increases.
In other words, yes, the closer the match between encoding and retrieval context, the easier it will be to remember (retrieve) the information. And the more different contexts you have encoded with the information, the more likely it is that one of those contexts will match your current retrieval context.
A concrete example might help. I’ve been using a spaced retrieval program to learn the basic 2200-odd Chinese characters. It’s an excellent program, and groups similar-looking characters together to help you learn to distinguish them. I am very aware that every time a character is presented, it appears after another character, which may or may not be the same one it appeared after on an earlier occasion. The character that appeared before provides part of the context for the new character. How well I remember it depends in part on how often I have seen it in that same context.
I would ‘learn’ them more easily if they always appeared in the same order, in that the memory trace would be stronger, and I would more easily and reliably recall them on each occasion. However in the long-term, the experience would be disadvantageous, because as soon as I saw a character in a different context I would be much less likely to recall it. I can observe this process as I master these characters — with each different retrieval context, my perception of the character deepens as I focus attention on different aspects of it.