HUMAN MEMORY

Can’t remember what you had for dinner last Tuesday? Don’t worry if you can’t. Your brain’s just not classed that meal as worth remembering.

How do we learn?

Learning does not depend on a single faculty; different systems underpin the acquisition of personal experiences, facts, habits and skills. There are, however, general principles that apply across systems. For example, it’s better to use a learning strategy of little and often, with breaks between learning trials, rather than cramming the learning into a single session.

Another general principle is that the act of testing what has been learned can often be more effective than further learning trials. This finding has considerable potential importance for education, where testing is typically seen as a method to evaluate what has been learned rather than a method of enhancing learning.

At the level of brain function, it has been known for many years that some form of consolidation of the neurochemical trace left by the learning experience is necessary, and that this involves the hippocampus, which is a structure deep within the brain. Recently, controversies have erupted over whether consolidation is a single process or whether it goes on repeatedly, with the hippocampus gradually transferring information to other parts of the brain.

Recent work in Edinburgh suggests that some densely amnesic patients benefit substantially from a brief period in a quiet and darkened room following the learning experience, suggesting that their capacity for consolidation is reduced but still present. If there is indeed a second stage of consolidation, the question arises as to whether this is also impaired in amnesic patients and, if so, whether ways can be found to alleviate this deficit.

One very active research area concerns the effects of sleep on memory consolidation. There is good evidence to show that a period of sleep enhances learning, although the precise influence of different stages of sleep remains unclear. Indeed this may well depend on the type of learning involved.

Why do we forget so many things?

Forgetting gets a bad press! We all complain about it and psychologists publish endless papers on the fallibility of eyewitnesses and the dangers of therapists creating false memories of child abuse. So why and how do we forget?

Importantly, we forget selectively, remembering important things and novel experiences and forgetting routine details. If everything were equally retained, we would drown in information. The capacity to remember specific individual events and locate them in a time and place – termed episodic memory – requires some kind of mental filing system that appears to be able to sort the important from the trivial.

The memory failure of the eyewitness typically occurs when seemingly trivial detail suddenly becomes important. False memories in such situations often result from pushing the witness’s memory into areas of uncertainty, where an “I don’t recall” response would be more accurate.

Does emotion play a role in wanting to forget something? Do we repress stressful events and, if so, does that repression inevitably have a dire impact on our future mental life? There is growing evidence that we can actively suppress unwanted memories. But it is also possible for therapists to induce totally false memories.

Even with genuine trauma cases, is reliving the memory of the event necessarily helpful? Encouragement to recall such memories can, for some people, be even worse than suppression.

Broadcaster and author Melvyn Bragg, for example, was recently profiled by the BBC. He confessed that a constant shadow had been cast by the suicide of his first wife. He decided to face up to the issue and produced a novel called 'Remember Me. Unfortunately', it made him even more distressed. Facing up to upsetting memories may sometimes help, but we still do not know when or how best to do it.

What is working memory and can it be trained?

Try multiplying 24 x 7 in your head, then do it with the aid of pen and paper. Next, try to describe how to get from your home to the nearest supermarket.

Both of these require a system known as working memory. It allows us to temporarily hold information in mind while working on it to solve problems or plan future activities. It is separate from long-term memory and densely amnesic patients can have perfectly normal working memory.

Measures of working memory have proved to be highly predictive of many activities, from understanding complex prose to acquiring a new computer language or solving reasoning questions from a standard IQ test. More recently, tests of working memory have been applied to schoolchildren and showed that working memory measures are able to predict scholastic problems, with different patterns associated with different types of difficulty.

For example, a deficit in a part of working memory concerned with brief storage of words and sounds can result in reading difficulties and problems in second language learning. Equally, impairment of the attention-control component can result in problems of concentration and Attention Deficit Disorder. Such children often go undetected by teachers, simply being described as ‘dreamy’ or unmotivated. Methods of identifying and helping such children are now being developed.

A particular controversy concerns the question of whether or not working memory can be trained. Dramatic results were produced by Swedish  neurologist Torkel Klingberg at the Karolinska Institutet in Stockholm, leading to much excitement  and many commercial products that attempted to capitalise on Klingberg’s ideas. Training involves a series of attention-demanding tasks that resemble computer games, some involving visual and some verbal material, and all gradually increasing in difficulty as learning progresses. So far, the evidence suggests that performance on the tasks improves and that this improvement will generalise to other tasks of similar nature.

Unfortunately, however, this does not typically lead to enhanced academic performance. It remains an open question as to exactly what is being trained  in these studies. My own view is that it is concentration and the ability to resist distraction  that’s being trained, rather than memory capacity. It’s unclear whether a way can be found to  bridge the gap between the improved skill and its practical application. If a method was revealed, it could help students  with Attention Deficit Disorder to cope with the challenges of the educational system and beyond.

Written by Alan Baddeley in "BBC Knowledge", UK, May 2016, excerpts pp. 30-31. Digitized, adapted and illustrated to be posted by Leopoldo Costa.