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If you can speak two or more languages, you’re likely to have some real advantages in life. For starters, you can talk easily with lots more people, and turn off the subtitles on more movies.
Are there cognitive benefits to bilingualism? That is, does being bilingual help you think better?
Newcomers to the field of psychology and neuroscience often want to learn as much as they can about a student’s memory system.
After all: when students learn something new, that means their memory has changed. So, if we know how memory works, then we’ll know how learning happens.
Alas, it’s not that simple.
It turns out that we have many different memory systems. We can’t simply learn how one of them works; we have to understand them all.
Key Distinctions
In the first place, we need to distinguish between long-term memory, and other short-term memory systems.
For example: if I ask you for your business phone number, you pull that number out of your long-term memory. After all, you know it quite well.
As I then walk across the room to write that number down, I hold that number in my short-term memory. (Probably I’m rehearsing it in my head, or even saying the numbers quietly.)
If, however, I decide to engage in some quick mental exercise, I might try to add together all the digits in your phone number. In that case, I’m not only holding those numbers in short-term memory, I’m also combining them in working memory.
I haven’t even written your number down yet, and already we’ve got three at least different memory systems at play.
Subtler Still
Of course, we can subdivide each of these categories in many different ways.
Long-term memory, for instance, includes at least two sub-categories.
Explicit memory records facts and events. I know that the Ideal Gas Law states that PV=nRT (fact). I know that yesterday was my mother’s wedding anniversary (event).
Implicit memory, by contrast, records processes: how to do things. Muscle memory is implicit. So is your knowledge of your native language’s grammar. You know how to juggle, and how to conjugate the auxillary verb “should”–even though you probably can’t say exactly how you’re doing those things.
In schools, we seem to focus a great deal on explicit memory: we want our students to know all sorts of facts.
However, we also want them to learn procedures: how to integrate a quotation into a subordinate clause, or how to solve for three variables with three equations.
Initially, our students learn these skills explicitly, but with enough practice they can do them without having to think about it. At that magic moment, their explicit memory has become implicit.
Brain Structures and Memory
We’ve known for a long time that explicit and implicit memory formation takes place in different parts of the brain.
Those of you who know the story of Henry Molaisson know that surgeons removed his hippocampi to relieve his debilitating epilepsy. The operation (mostly) cured this medical problem, but created a profound cognitive problem: he could no longer form new explicit memories.
That is: if he practiced drawing a complex figure every day, he didn’t remember from one day to the next that he had practiced doing so the day before; he couldn’t remember the event.
However–and here’s the key point–HE GOT BETTER AT DRAWING THE FIGURE. That is, he didn’t form explicit memories of practicing, but he did form implicit memories of the new skill. He knew how to do it.
Clearly, the hippocampi are essential for explicit memory formation, but not for implicit memory formation.
Larry Squire’s article Memory systems of the brain: A brief history and current perspective provides a helpful overview of different memory systems, and the places in the brain that house them.
(The Henry Molaisson story is often told. Although controversial, Suzanne Corkin’s book Permanent Present Tense is probably the best place for an extended exploration of HM’s life, and the scientific information learned from it.)
Today’s News
A recent article in the journal Neuron argues that explicit and implicit memory differ not only in their location in the brain, but also in the frequency of their neural signatures.
As you can see in the diagram above, gamma waves oscillate quite rapidly–up to 100 times per second–whereas delta waves oscillate slowly–fewer than 3 times per second.
(Wikicommons has a helpful visualization of different oscillation rates here.)
This article suggests that explicit memories show an increase in the alpha/beta range (10-30 Hz), whereas implicit memories produce an increase in theta waves (3-7 Hz).
In other words: explicit and implicit memories record different kinds of information, operate in different parts of the brain, and produce increases in different kinds of brain waves.
As of yet, there are no specific teaching implications to these research findings. However, they underline the point where this argument started: we can’t simply study a student’s memory system, because each student has so many (and so complex) memory systemS.
Little wonder, then, that teaching and learning can be so challenging. And, of course, so much fun.
Self-determination theory, developed by Edward Deci & Richard Ryan, argues that people are motivated by a desire for three things: autonomy, relatedness, and competence.
(Here‘s a handy place to brush up on self-determination theory.)
This theory suggests that teachers can motivate students by creating lesson plans and classroom environments that promote all three.
As is always true, such broad categories identified by researchers might not be easy to translate into specific classroom practices that work for my students.
For example: What kind of metacognition is appropriate for 1st graders?
How, exactly, can I instill a growth mindset in high-schoolers? (I know: “process praise” in place of “person praise.” But what exactly does that sound like for a 16-year old?)
And: if I want to put self-determination theory to work, what precisely does autonomy look like in the classroom?
Of course, the answer to that question will be different for each of us. To get that conversation started, here‘s an article over at Edutopia listing a few strategies to promote classroom autonomy.
Some of these might be helpful for your students; some not. But, in any case, they’re a useful prompt for our own thinking about the appropriate kind of autonomy to motivate our own students.
When you see claims for an exciting new brain training finding (the headline crows “Dementia Breakthrough? Brain training game ‘significantly reduces risk’ “), you can expect to see the skeptics respond very quickly.
As the Guardian reports, the study didn’t follow rigorous definitions of dementia–it allowed participants to self-report!–and their results didn’t consistently reach statistical significance.
We ardently hope that someday we’ll find brain-training games that work. Perhaps later research will reveal these games to be effective.
For the time being, however, it seems the best we’ve got to reduce the likelihood of dementia is lifestyle changes: exercise being the best option.
I’ll see you on the jogging track tomorrow morning…
