The reasons we remember some things and not others had always struck me unclear and even arbitrary. Memory’s mercurial character was revealed to me early in life when algebraic equations, irregular French verb forms and the conditions for use of the subjunctive case slipped and tumbled instantly from the armature of consciousness. The phone numbers of elementary school friends, meanwhile, acquired a firm and immediate grasp that has lasted a lifetime.
But the volatility of human recall becomes increasingly apparent as we get older, and recently I was finding myself ever more mystified by which things are fastened to my mind and which are not. How is it that I am able to remember every ingredient, measurement and belabored instruction for mushroom risotto while the sequence of numbers in my son’s street address slips my mind every time?
So I turned to Christine Weber, Ph.D., a clinical neuropsychologist in Seaford, N.Y., who has an explanation for some of the variations in how the mind compiles its records. She says they’re due to the differences between what it is called explicit and implicit memory.
Explicit memory has to do with the kind of information we consciously try to remember. It includes anecdotes, appointments, events, the title of the movie you saw last week or the speaker at your college graduation — things that are "episodic" in nature. Explicit memory can also be autobiographical: the date of your wedding or a friend’s birthday. This data requires reflection and recollection because it hasn’t been sufficiently absorbed into the interior rhythms of your everyday life.
Implicit memory, also known as procedural memory, is less conscious. It involves those things that are learned so thoroughly and recalled so often that little mental effort goes into summoning them. While implicit memory covers such physical skills as ice-skating and yoga, it can also extend to more cerebral endeavors, such as sketching an architectural plan or copyediting a manuscript. “Once you know something,” Weber says, “then you’ve got it.”
Weber's explanations have helped me to make sense of the confounding aspects of human recall. My son moved to his apartment a year ago. I have only visited a couple of times and have had few opportunities to write his address — i.e., to “encode” the new information — whereas I have made mushroom risotto numerous times.
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The good news, Weber tells me, is that while explicit memory can slow with age, becoming less adept at picking up and retaining new information, implicit memory is more deeply ingrained and thus less impaired by time.
And what endures could be anything, says Herb Gingold, Ph.D., another New York-based psychologist who works in this field. “There are no rules for this. It depends on the focus of the person’s life.
“Whatever you have mastered in your life is what will remain with you,” he continues. “If you are a musician, for example, what will stay with you are a sensitivity to sound and the understanding of the language of music. But it can be any type of knowledge: You could be a physicist or someone who does sudoku or crossword puzzles. Or knits or draws. [Implicit memory] is about knowing the rules and how to make whatever you are doing work.”
It’s reassuring to learn that memory is not as indiscriminate and capricious as it often seems, and it’s an even greater comfort that we can choose to master and retain certain types of knowledge.
For me, it’s heartening to know that even as I struggle to summon up phone numbers, titles, surnames, timelines and appointments, at least I will retain the chords in Vivaldi’s second movement of "Winter"; the resonance of my children’s voices; how to roll out a pie crust, structure a sentence, do the breaststroke — that tapestry of sounds, textures, words and gestures that have become encrypted in my life, enriching it and making it what it is. The familiar rhythms and patterns of language, thought and motion that most define my life seem to be here to stay.
And if there is any question about which memory cabinet I am trying to open, I recall Oscar Wilde’s line — “Memory is the library we all carry about with us” — and picture an archive resting on a solid foundation and containing its own system of shelving, organized catalogs and stores of well-ordered volumes. Such an image, implicitly or explicitly, seems worth remembering.