A memory researcher explores the science — and value — of forgetting

Dr. Scott Small has spent much of his career studying Alzheimer's disease. Alzheimer's, of course, is something many of us fear because of the way it can steal our memories and cause us to forget our lives and loved ones.  

So it's somewhat strange that Dr. Small would write a book extolling the value of forgetting.

But a couple of decades of research into the way memory works — and the way it doesn't — has led him to the conclusion that forgetting, at least under normal circumstances, is essential. It's not a failure of our minds, which is how we usually think of it, but is actually key to how our minds work.

In fact, in his new book, Dr Small argues that our cognition, the power of our minds to abstract, manipulate ideas and solve problems, depends on forgetting. And that sometimes forgetting may even lead us to be happier and make better decisions in our lives.

Dr. Scott Small is Director of the Alzheimer's Disease Research Center and Professor of Neurology and Psychiatry at Columbia University in New York. His new book is called Forgetting: The Benefits of Not Remembering.

He spoke with Bob McDonald on Quirks & Quarks about his book.

This interview has been edited for length and clarity

I mentioned that most of us think of forgetting as a mental failure — our brains not working right — when we can't remember names or where we left the keys. When did you first start to realize the value of forgetting? 

My whole career was based on the premise that more memory is always the noble goal, and forgetting of any kind should be fought tooth and nail. And that's why it was eye-opening to me to really start reading the new science of normal forgetting, which essentially argues that it's required for successful happy living. 

You spend some time in the book explaining how forgetting and memory work in the brain. Take me through that. 

The premise of the book emerges out of a fundamental observation, and that is that our neurons have separate nanomachines, one dedicated to growing neurons, the tips of neurons that underlie memory. It used to be thought that the forgetting process, the wilting back down of those tips were simply that machinery rusting, malfunctioning, not working well enough.

Well, it turns out there's a whole separate group of tiny little machines in our neurons that are exclusively and distinctly dedicated to wilting back down those neuronal tips. And so it raises the interesting question if nature has endowed us with these separate machines, is that just a coincidence?

It probably does serve a purpose and I review insight from neurology, psychology and even philosophy that argues that you, in fact, do need memory and forgetting — in balance — to be able to live happier and smarter lives. 

You suggest we might get some insights into the value of forgetting from autism. Tell me about that.

Please allow me to quickly say, autism, many neurologists and psychiatrists consider it a disorder. You probably know that many people who have autism or family members who have people with autism in their families sometimes object to that. It's biodiversity; it's not one disorder, it's many disorders. I think that means we need to be sensitive to that. 

But with that said, many of the genes that are linked to autism are exactly linked to those nanomachines in our brains that govern forgetting. So in a very simplistic sense, some people with autism simply have their memory/forgetting balance thrown off kilter with too little forgetting.

One of the defining features for a clinician to diagnose someone with autism is this difficulty with dealing with new situations. People with autism become very anxious in those situations. And that's why they often like to engage in repetitive behaviour in familiar activities, and now with the new science of forgetting, one of the reasons why that occurs is because anything that's novel is anxiety provoking.

That's one interpretation of why people with autism really prefer to engage in repetitive, familiar behaviour. 

Can you give me an example of how forgetting helps with [cognitive skills like] generalization? 

It's actually not so much neuroscience that was most informative, but it was computer science. To recognize a face, one would imagine that you would need more and more memory. It turns out that you need a memory balanced with forgetting and that comes out of computer science.

One of the great utilities of computers is to identify a face, right? Let's assume that face suddenly grows a mustache or puts on a hat or wears glasses in contrast to the picture I have stored in my databases. You might think that in order for a computer to recognize that face, you want to bestow that computer with more and more memory.

In fact, what the computer algorithm needs is to balance memory with forgetting, because if there's no forgetting, the computer gets too stuck on details. They will not be able to extract the whole if there's suddenly a mustache, if that person is suddenly wearing a hat. So you need to be able to forget, so that your brain and the computers don't get stuck on minute details. 

I'd like to talk about someone that you mention in your book, 'Dr. X,' a physician who consulted you. He was a great doctor, but he had a terrible memory. What insight did you get from that experience? 

He's a great doctor — an infectious disease expert. And yet throughout medical school — I went through medical school, I know how much having a great memory is useful to ace your exams — but he came to me basically to validate his hunch that his memory, his hippocampus in this case, wasn't functioning at a very high level. He was normal, but he didn't score very high on his memory scores.

But because he learned he cannot rely on his memory, he had to slow down his decision making. And because of that forced slowness, at least in diagnostic medicine, that has worked to his favour because if he didn't get there first, he got there a little bit later, but typically [was more likely to make] a right diagnosis than others. And in the book, I came up with this slightly cutesy phrase that the tortoise mind always wins against the hare brain. 

I'm not dissing on memory. Having a great memory is fantastic if you're a chess player, a poker player. But this is just an example of where having a memory that's not extraordinary actually worked in the favour of this particular profession, the diagnostic physician. 

You also write about post-traumatic stress disorder, which is something that you personally had close contact with, as a failure of forgetting. Tell me about that. 

I'm a memory doctor. I try to fix broken memory. So it raises the question, 'Are there true disorders where there's broken forgetting?'

PTSD, almost by definition, is a disorder where your emotional forgetting is malfunctioning.

If you just think about it, we all experience emotional traumas. We don't always forget the details — but for those of us who somehow don't have that braking system, our emotional memories are running too fast or burning too hot, and they become all consuming. So in many ways, PTSD is a classic example of what happens when our emotional forgetting goes awry.

Well, after reading your book and getting the value of forgetting, should I celebrate the next time I misplace my keys? I mean, it shows my brain's working as it should? 

We all forget keys. We all forget names throughout our lives. If you're noticing worsening as you age, you have to wonder.

But if it's the way you've always been, then it's just part of a normal forgetting. After writing the book, I've actually been much more relaxed about my memory blanks — when I can't think of that person's name or that actor's name. 

And you know what happens when you relax, when your brain relaxes, you actually remember better.

Produced and written by Jim Lebans. Click on the link at the top of the page to hear the interview with Dr. Scott Small.