Speak, Memory, Vladimir Nabokov called his book about his childhood years, and in this incantatory title we can hear our human dread of forgetting. “The cradle rocks above an abyss, and common sense tells us that our existence is but a brief crack of light between two eternities of darkness,” reads the book’s first sentence. The crack of light may be described as memory itself—that fickle and unreplicable network of experience and associations from which we construct who we are, who others are, and what we may expect from them and from ourselves.
In the broadest sense, memory is consciousness, because what the brain is doing at all times and in all of its operations is remembering. More often than not, it is a matter of practical cognition: knowing where we left the keys, and then, once we have located them, what the keys are for. But within such memories are vestiges of our emotional and sensorial lives, an intimate network of recollections, unique to each of us, that keys conjure. The neurosystem in which this cascade of memory occurs, with its branches and transmitters and ingeniously spanned gaps, has an improvised quality that seems to mirror the unpredictability of thought itself. It is an ephemeral place that changes as our experience changes, to the point where we are incapable of remembering the same event in exactly the same way twice.
In her fascinating book about memory loss and the efforts of scientists to understand it, Sue Halpern reports an experiment in which members of the Cambridge Psychological Society were asked to reconstruct a meeting of the society that had taken place two weeks before. The average person was barely able to recall 8 percent of what had happened, and almost half of this was incorrect, peppered with the recollection of events that had never occurred or that had occurred elsewhere.
Such paltry power of retrieval in an educated, and supposedly attentive, group is not surprising. Memory, Halpern reminds us, “is not an archive,” nor does it record in real time. It lives in the brain “in chemical traces. The traces can fade…and they can be augmented,” depending on one’s experience and observation. The intensity of an experience may sharpen the memory of it, while making it even less accurate. During situations of extreme stress, for example, the body is flooded with damaging amounts of the hormone cortisol, causing communication relayed by neurotransmitters and other chemicals in the brain to break down. Halpern recounts the case of an Australian forensics expert named Donald Thomson who was a guest on a television show devoted to exploring the unreliability of eyewitness testimony:
Not long afterward [Thomson] was summoned to a police precinct, put in a lineup, and identified by a woman as the man who had raped her. Though he had an incontrovertible alibi—he was on national television at the time of the attack and seen by hundreds of thousands of viewers—he was charged with the …