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In a recent news report, I talked about how walking through doorways creates event boundaries, requiring us to update our awareness of current events and making information about the previous location less available. I commented that we should be aware of the consequences of event boundaries for our memory, and how these contextual factors are important elements of our filing system. I want to talk a bit more about that.

One of the hardest, and most important, things to understand about memory is how various types of memory relate to each other. Of course, the biggest problem here is that we don’t really know! But we do have a much greater understanding than we used to do, so let’s see if I can pull out some salient points and draw a useful picture.

Because it holds some personal resonance for me, my recent round-up of genetic news called to mind food allergies. Now food allergies can be tricky beasts to diagnose, and the reason is, they’re interactive. Maybe you can eat a food one day and everything’s fine; another day, you break out in hives. This is not simply a matter of the amount you have eaten, the situation is more complex than that. It’s a function of what we might call total allergic load — all the things you might be sensitive to (some of which you may not realize, because on their own, in the quantities you normally consume, they’re no or little problem). And then there are other factors which make you more sensitive, such as time of month (for women), and time of day. Perhaps, in light of the recent findings about the effects of environmental temperature on multiple sclerosis, temperature is another of those factors. And so on.

Here’s an interesting study that’s just been reported: 72 seven- and eight-month-old infants watched video animations of familiar fun items being revealed from behind a set of colorful boxes (see the 3-minute YouTube video). What the researchers found is that the babies reliably lost interest when the video became too predictable – and also when the sequence of events became too unpredictable.

In other words, there’s a level of predictability/complexity that is “just right” (the researchers are calling this the ‘Goldilocks effect’) for learning.

Now it’s true that the way babies operate is not necessarily how we operate. But this finding is consistent with other research suggesting that adult learners find it easier to learn and pay attention to material that is at just the right level of complexity/difficulty.

The limitations of working memory have implications for all of us. The challenges that come from having a low working memory capacity are not only relevant for particular individuals, but also for almost all of us at some points of our lives. Because working memory capacity has a natural cycle — in childhood it grows with age; in old age it begins to shrink. So the problems that come with a low working memory capacity, and strategies for dealing with it, are ones that all of us need to be aware of.

Today, I want to talk a little about the effect of low working memory capacity on reading comprehension.

A recent study involving 400 University of Alberta students found that 5% of them had reading comprehension difficulties. Now the interesting thing about this is that these were not conventionally poor readers. They could read perfectly well. Their problem lay in making sense of what they were reading. Not because they didn’t understand the words or the meaning of the text. Because they had trouble remembering what they had read earlier.

Impaired vision is common in old age and even more so in Alzheimer’s disease, and this results not only from damage in the association areas of the brain but also from problems in lower-level areas. A major factor in whether visual impairment impacts everyday function is contrast sensitivity.

Contrast sensitivity not only slows down your perceiving and encoding, it also interacts with higher-order processing, such as decision-making. These effects may be behind the established interactions between age, perceptual ability, and cognitive ability. Such interactions are not restricted to sight — they’ve been reported for several senses.

In fact, it’s been suggested that much of what we regard as ‘normal’ cognitive decline in aging is simply a consequence of having senses that don’t work as well as they used to.

The effects in Alzheimer’s disease are, I think, particularly interesting, because we tend to regard any cognitive impairment here as inevitable and a product of pathological brain damage we can’t do anything much about. But what if some of the cognitive impairment could be removed, simply by improving the perceptual input?

I don’t often talk about motor or skill memory — that is, the memory we use when we type or drive a car or play the piano. It’s one of the more mysterious domains of memory. We all know, of course, that this is a particularly durable kind of memory. It’s like riding a bicycle, we say — meaning that it’s something we’re not likely to have forgotten, something that will come back to us very readily, even if it’s been a very long time since we last used the skill.

For several decades there’s been argument over where motor memory is created. Now at last the dispute has apparently been settled, in favor of both contenders. What we needed to clarify the evidence was to realize that short-term motor memory is a quite different animal from long-term motor memory, and the two are created in different places.

The differences between short- and long-term motor memory have important implications, so let’s take a look at them.

I recently reported on a study showing how the gestures people made in describing how they solved a problem (the Tower of Hanoi) changed the way they remembered the game. These findings add to other research demonstrating that gestures make thought concrete and can help us understand and remember abstract concepts better.

For example, two experiments of children in late third and early fourth grade, who made mistakes in solving math problems, have found that children told to move their hands when explaining how they’d solve a problem were four times as likely to manually express correct new ways to solve problems as children given no instructions. Even though they didn’t give the right answer, their gestures revealed an implicit knowledge of mathematical ideas, and the second experiment showed that gesturing set them up to benefit from subsequent instruction.

I recently reported on a long-running study that found that husbands or wives who care for spouses with dementia are six times more likely to develop Alzheimer’s themselves than those whose spouses don't have it. The most likely cause for this is the great stress of caregiving. Both stress and depression increase the risk of Alzheimer’s, and both are common (well, stress is inescapable!) among caregivers.

There was an alarming article recently in the Guardian newspaper. It said that in the UK, diabetes is now nearly four times as common as all forms of cancer combined. Some 3.6 million people in the UK are thought to have type 2 diabetes (2.8 are diagnosed, but there’s thought to be a large number undiagnosed) and nearly twice as many people are at high risk of developing it. The bit that really stunned me? Diabetes costs the health service roughly 10% of its entire budget. In north America, one in five men over 50 have diabetes. In some parts of the world, it’s said as much as a quarter of the population have diabetes or even a third (Nauru)! Type 2 diabetes is six times more common in people of South Asian descent, and three times in people of African and African-Caribbean origin.

Why am I talking about diabetes in a blog dedicated to memory and learning? Because diabetes, if left untreated, has a number of complications, several of which impinge on brain function.

I talk a lot about how working memory constrains what we can process and remember, but there’s another side to this — long-term memory acts on working memory. That is, indeed, the best way of ‘improving’ your working memory — by organizing and strengthening your long-term memory codes in such a way that large networks of relevant material are readily accessible.

Oddly enough, one of the best ways of watching the effect of long-term memory on working memory is through perception.

Perception is where cognition begins. It’s where memory begins. But here’s the thing: it is only in the very beginning, as a newborn baby, that this perception is pure, uncontaminated by experience.

‘Uncontaminated’ makes it sound bad, but of course the shaping of perception by experience is vital. Otherwise we’d all be looking around wide-eyed, wondering what was going on. So we need to shape our perception.

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