When Casey told her son
Will that the Weisses were coming over for dinner that night, his
response took her by surprise: "Don't forget the
strawberry cupcakes." Three-year-old Will was recalling that
the Weiss' son liked the cupcakes Casey had served at a dinner
party eight months earlier, when he was only two. As precocious as
his memory might seem, though, by the time Will reaches school age,
the strawberry cupcakes will be gone, along with his recollections
of most, if not all, of his first three years.
Psychologists refer to this as "childhood amnesia." But
it only applies to certain kinds of memory — kids retain plenty of
information from the early years. If Will's dad teaches him to
throw a baseball, he may remember how for the rest of his life. Not
only that, but the emotional memories of childhood have a lasting
impact. Long after the image of the cupcakes has faded, Will might
be left with warm feelings towards sweets and social gatherings.
Researchers now know this is because the brain doesn't have
just one record button. By studying healthy kids as well as adults
who have lost certain kinds of memory completely, psychologists
have come a long way in explaining how early childhood can be so
formative long after our memories of these years have completely
vanished.
The most famous
patient in brain research, Henry Molaison, known for decades as
H.M., passed away recently in a nursing home in Connecticut. Born
in 1926, he suffered from severe epilepsy until, at age
twenty-seven, he underwent a radical surgery in which doctors
removed two slivers deep in his brain, just at ear level. When H.M.
woke up, his seizure disorder was cured, but he had lost the
ability to form new memories. He remembered his childhood, but,
from the time of the surgery until his death at age eighty-three,
new memories stayed in his consciousness for about twenty seconds
and then disappeared. A lot of what we know today about how memory
develops began with H.M. It turns out that for the first few months
of life, babies operate much like the famous amnesiac. Babies then
gradually become more skilled at memory as the part of their brain
that H.M. lived without begins to grow.
Even though their memories are
just beginning to ripen, newborns are surprisingly good at knowing
what they've seen or heard before, a skill referred to as
recognition. To test the abilities of the tiniest babies,
researchers take advantage of the infant sucking reflex. When they
are given a pacifier that controls what they see or hear, depending
on how fast they suck, babies just days old will adjust their
sucking rates to spend more time looking at a picture of mom's
face, or listening to the words of a book she read aloud in her
pregnancy. The fact that a baby recognizes what is familiar to her
(and prefers to see and hear her parents) means that, in some form,
she is storing memories of her experiences right from the
start.
An experiment
designed by Carolyn Rovee-Collier in the 1970s is still used today
to test just how long infant memories are stored. Researchers lay a
baby on her back so that she's looking up at a mobile. They tie
the mobile to the baby's foot with a ribbon so that when she
kicks, the mobile comes to life. The baby quickly learns to kick
more vigorously to watch the mobile dance. Then, after days have
passed without any exposure to the set up, she is put back in her
crib with the mobile, but it's no longer attached to her foot.
When they see the mobile, most babies start to kick furiously,
remembering the fun they had with it days before. Two-month-olds
remember if they are tested a day or two later, while
six-month-olds remember for about two weeks.
To continue reading "Memento," click here.
