Can you trust your memory?

Sandra Parshall

Forget everything you ever believed about memory.

Neuroscientists have decided they got it wrong the first time around – instead of being hardwired into the brain, unchangeable, a memory is dynamic and can be distorted or drastically altered by current experiences. There may be no such thing as a totally accurate memory.

Of course, ordinary people have always known that we have gaps in our memories, that we sometimes “misremember” things, but we don't seem to doubt the accuracy of the memory itself; we just assume our conscious minds are having trouble accessing it. Police and prosecutors have always known that eyewitness testimony is unreliable – question 20 witnesses to a crime and you’ll probably get 20 different accounts of what happened and what the perpetrator looked like. Yet the human faith in the rock-solid truth of memory is so strong that juries send people to prison solely because eyewitnesses have identified them, and we argue to the point of blows over “what really happened” during a pivotal event.

Until a few years ago, neuroscientists believed that once a memory was physically implanted in the brain, there it stayed in its original form unless destroyed by disease or injury.

The flaw in the old theory of unchanging memory became obvious in the early 1990s when a startling number of people began recalling “repressed memories” of childhood sexual abuse. After a while the situation resembled the Salem witch hunt, which is now considered a sort of group hallucination. Families were torn apart. Innocent people were branded as pedophiles. Some of those memories of abuse may have been real. Some may have been knowingly fabricated. But many were apparently planted in vulnerable minds, however unintentionally, by therapists. A few people heard and read so much about repressed memories that they started believing they’d been abused as kids too. If the false memory of horrifying events could be created by suggestion, what other manipulations of memory were possible?

My own fascination with that question resulted in my first published novel, The Heat of the Moon. Until the final title popped up while I was writing Chapter 11, the book’s working title was Memory. It’s interesting to note that one editor who rejected the book said she simply didn’t believe that anyone’s memory could be manipulated.

That editor’s opinion aside, hundreds of experiments and studies in the past decade have led to the same conclusion: memories are highly malleable, they have a lot in common with imagination, and we are constantly revising them. The more often we recall an event, the more likely we are to embroider it with imagined details, and because it’s so clear in our memories, we’re certain it happened exactly that way. (Hillary Clinton’s account of leaving a plane under nonexistent sniper fire, a story she obviously believed, is a perfect example.)

A memory is a chemical reaction in the brain, involving more than a hundred proteins. Electrical impulses (aka sensory information – sights, tastes, smells, etc.) set the process in motion, and the thing we call a memory ends up in the amygdala, which is the size of an almond, and the tiny, banana-shaped hippocampus. Everything we have ever experienced, thought, desired, feared – everything that makes us who we are – resides in these astonishingly small storage spaces inside our skulls. But we frequently haul out our memories, handle them, share them, expose them to our current experiences, and every time we access them we may change them slightly. Our emotional state today can alter our memories of what happened years ago.

All this may create problems for a prosecutor who needs reliable eyewitnesses, but it may offer a way back to peace of mind for combat veterans, rape victims, and others tormented by post-traumatic stress disorder. Every recall of a frightening memory sets off a chemical reaction in the brain that can reinforce or magnify the original terror. But what would happen if the mind were prevented from making all the chemical connections that produce fear?

A few psychiatrists and psychologists who treat patients with PTSD are taking a new approach based on a better understanding of how the brain processes memories. They give a patient propranolol, a common, safe medication for high blood pressure that also happens to block some of the chemical reactions in the brain that reinforce frightening memories. While the patient is on propranolol, he deliberately calls up the traumatic memory, but because propranolol prevents his brain chemistry from going haywire, he is able to remember the entire experience more calmly. After a series of such “treatments” most patients are no longer at the mercy of their past traumas. Will the benefit last? At this point, no one knows, but if it does, it may lead to new ways of treating anxiety disorders, phobias, even addictions.

Our memories tell us who we are and where we came from. An amnesiac – or a victim of Alzheimer’s – has no identity. Because our memories are essential to our sense of who we are, it’s more than a little scary to admit that they aren’t totally reliable. It’s always disconcerting to find that someone who shared an experience with us remembers it in a radically different way, with details we don’t recognize. With so much scientific evidence of the memory’s malleability accumulating, though, we may have to admit that each of us sees the past through a distorted filter. If researchers could give us a foolproof way to remember where we put our car keys, all the rest might be easier to swallow.

How would you rate your memory? Have you ever argued with your spouse or a friend or a sibling about your differing accounts of an event or a place? Have you ever been shocked to find proof that something you remember vividly didn’t actually happen?