Earlier today I entered the pantry off
the kitchen, paused a moment, and then had to admit I had no idea why I was
there. I had wanted something, evidently, but whatever it was escaped me. At my
age I would be worried about that but for the fact that I commonly did the
exact same thing at age 12. Since my memory in academic matters was (as it still
is) pretty good, my mom called me “the absent-minded professor.” She was being
polite. My mind was simply occupied by something else at those moments, and
that something else crowded out the original intended task. By the way, I was
after a garbage bag as I remembered the next time I looked at the bin by my
desk and noticed it needed a liner. We all have had similar experiences.
Suppose you wish to stop at a convenience store that is located a short
distance beyond a left turn that you commonly take on your drive home. If your
mind is preoccupied you are very likely to take that left turn before you
realize your mistake. (A friend was once so preoccupied he drove to a local
hospital and parked in the parking lot before realizing that there was no
reason for him to be there – there hadn’t been for a year. “I’m losin’ it!” he
said to me on his return. He wasn’t. It was just a glitch he never repeated.) There
is more to forgetfulness than just distraction, whether by our own thoughts or
the world outside. It long has been known that there are separate mechanisms
for short and long-term memory. To kick something into long-term memory you
either must think about it for a little while or have some emotional response
to it. Otherwise it vanishes. As an example we again can use that route home
you commonly drive. Odds are that ten minutes after you get home you won’t
remember most of the drive – only the parts that concentrated your attention
for some reason. By tomorrow you will have forgotten most of those parts too.
This is one reason (among many) why eyewitness testimony is so notoriously
unreliable; we usually don’t know until after the event that what we saw was
important, so our attention probably wasn’t concentrated on the scene as it
happened. These two tiers of memory have been
recognized for decades. But until recently the fading of long-term memories was
regarded as serving no useful purpose. In recent years, however, mechanisms of
active forgetting have been found to exist in the brain. Our minds
“deliberately” (non-consciously but by normal function) weed out memories they
tag as useless. This would not have evolved unless there was an advantage to
selective forgetting. In his book Forgetting:
The Benefits of Not Remembering Scott A. Small explains what they are.
Dr. Small is the director of the
Alzheimer’s Disease Research Center at Columbia University. His studies of
patients suffering from pathological forgetting – not just from Alzheimer’s but
from other causes such as injury – led him to examine the difference between
this and “routine” forgetting. We are deluged with information from our
five senses constantly. Were we to remember all of it there would be too much
data for our brains to process. We would freeze up and would have trouble
generalizing as we are overwhelmed by details. “As our brains intrinsically
know, not everything we store is worth remembering, and there is a real
advantage,” Small writes, “to forgetting details of the world we temporarily
encode.” Many autistic people have excessively detailed memories and consequently
get upset by minor changes in the environment – a book out of place in a
bookcase for example – that most of us never would notice. They notice because
they remember exactly the way the bookcase looked yesterday. PTSD is another
condition of remembering too much – in this case obsessively. Much of the memory pruning occurs during
sleep when important memories are reinforced and trivial ones are discarded. Our
nonconscious minds are pretty good at determining which is which. This is why
it is useful to sleep after cramming for a test. Small goes to some length to
detail the neural processes by which memories are either strengthened or
destroyed. In recent years technology has advanced enough to view these
processes directly. In an interview with Psychiatry News Small explained, “The
ability to forget helps us prioritize, think better, make decisions, and be
more creative. Normal forgetting, in balance with memory, gives us the mental
flexibility to grasp abstract concepts from a morass of stored information,
allowing us to see the forest through the trees.” So the purpose of forgetting is
remembering – remembering what is important. As with every other trait, humans
fall along a spectrum in their capacity to remember and forget. There are super-rememberers:
actress Marilu Henner, for instance, who might remember what color dress she
wore on some randomly named date in 1982. Thanks to her job in front of a
camera, many of these memories can be verified. Then there are super-forgetters
who don’t remember what they wore yesterday. But both forget. Both forget most
of their lives. The super-rememberers (the condition is called hyperthymesia)
typically don’t even perform better on standard memory tests (e.g. reciting
lists of numbers or words) than average people. Their minds don’t tag these
lists as important and therefore memorable. Their memories instead tend to be
autobiographical: to whom they talked and what they had for breakfast on, say,
September 7, 1992. One still can see how this would be an advantage, though I
suppose “forgive and forget” is off the table. So, all of our memories are edited: a
balance of the forgotten and the reinforced. I have the forgetting part of the
equation down pat. How much that assists my remembrance of the rest is debatable.
But maybe it would be a good idea to write myself a note before going into the
pantry.
No comments:
Post a Comment