Great is the power of memory, a fearful thing, O my God, a deep and boundless manifoldness; and this thing is the mind, and this am I myself.

–Augustine

The Keys to Memory

What makes some events memorable while others seem irretrievable? If I look back to the time I was five years old, I know that a number of fairly significant things happened that year:  I started kindergarten, then moved from Colorado to Texas. My youngest sister was born. My father changed jobs twice. These were major life events, but my memories of them are vague. And yet, what sticks in my brain from that time period is the memory of hiding a pack of Dentyne gum, a treasure I’d hoped to keep from my younger sisters, under the clunky radio that sat on our kitchen counter, only to have my mother discover and share it with my sisters anyway. How did that moment get hardwired into my brain while more significant events escaped my recollection? How does memory work?

Memory is a huge subject, and you’ll find recommended reading on the subject in the From My Bookshelf section of this site, especially the chapters on memory in John Medina’s Brain Rules, and Daniel Schacter’s Searching for Memory. The following, however, is a basic introduction, excerpted from Half Past Perfect, a book I co-authored with Elizabeth Taylor, and which you can find in our Bookstore.

How the Brain Remembers

“For many years, experts believed that there was no brain structure directly associated with memory. Recent research, however, gives us clues about why and how memories are encoded, and what happens when we retrieve them. New technology allows researchers to look into a living, functioning brain. Neurologists and psychologists are now able to detect brain activity at the time memories are stored.

Memories are not stored perfectly whole, just waiting for us to retrieve them. Given our computer age, we might assume that a bit of information–say the scheduled time for your  dentist appointment–is stored as a digital file somewhere in the brain where it remains intact. When you need to retrieve that information, it’s like pulling up the file:  10:30 on October 14th.

But computers, unlike our brains, don’t relate facts to anything else. The human brain functions in a much richer, more complicated way. Human memories are not merely recorded, but constructed in response to an experience. Our memories are formed through the association of a number of facts. The time of your appointment is linked to the fact that your dentist’s schedule usually runs a half-hour behind, and that the office always smells like Lysol, mint and tooth polish. Different parts of the brain take note of the physical sensations and emotional impressions of the event, and establish a relationship between them to form a memory. Every time the relationship is recalled, it creates a ‘hard-wired’ connection in the brain. The more often that memory is retrieved–such as the telephone number of the house you lived in growing up–the stronger that connection becomes and the more vivid and lasting that memory will be.” (Half Past Perfect, p. 24)

So . . . what does this mean on a practical level?

Facts Are Filtered

“Our brains select which facts are saved in order to be available for future recollection. For example, when you showed up for your first day of school, your senses took in thousands of bits of information:  the smell of chalk dust, the sounds of crayons waxed over pulpy paper, the teacher’s voice and the tightness of your new shoes. Not all of the information made the cut. In order for that memory to be lasting, certain facts had to be selected and reinforced, while others were eliminated. … The function of selection is a good thing. It allows us to sort and categorize information. Being able to tune out non-relevant details enables us to focus on what we consider to be more valuable.” (Half Past Perfect, p. 26)

Sensory Memory

“It is an obvious fact that the information we gather about an event comes primarily through our five senses:  sight, sound, touch, taste and smell. It is less obvious how sensory detail is recorded and, later, recalled. Most people rely primarily on sight. When asked to describe someone, they will likely tell you what the person looks like.

However, when recalling a memory about an event or a person, all of our senses are clicking. Everyone has experienced the flood of memory that rushed in when we encounter a familiar scent. The smell of tuna or lilacs can evoke vivid, specific incidents or people, even decades after the fact. … Once a memory is triggered by one sensory detail, the pathway is opened to invite memory from other senses. The more senses involved in the original event, the richer the recalled memory will be.” (Half Past Perfect, p. 27)

Our Memories Tell Us Who We Are

“Our memories represent what we believe about our experiences. When we create memories, we include our emotional impressions as well as the meaning of each event. As neurologist Oliver Sacks wrote, i[i]t may be said that each of us constructs and lives a “narrative,” and that this narrative is us, our identities.’ Our personalities, our sense of ourselves are bonded to our stories. . . .  Understood this way, our tales become more than just lessons to be taught to children or entertaining anecdotes. Our stories are the medium we use to tell ourselves and others who we are.” (Half Past Perfect, p. 29)