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The
Herald
January 26, 2004
Baby memories trick of the mind
by Simon Collins; Science Reporter
Remember the day
when you fell out of your cot as a baby? Or your mum took you to the beach
aged one?
If so, Otago University psychologist Harlene Hayne
believes your memory is playing tricks on you.
Babies can remember things day to day, but people cannot remember things from
before they talk because they did not have the words to express them, her
research suggests.
"Somewhere between the ages of 3 and 4, people begin to have snippets of
memory," she says.
But most people have lost any true earlier memories through "infantile
amnesia".
Dr Hayne has won a $660,000 Royal Society Marsden grant to trace the way
children's ability to remember things improves as they get older.
The Oklahoma-born professor, who has two daughters aged 9 and 12 with her
husband, brain scientist Dr Mike Colombo, has become an expert on memory
development through 12 years of research in Dunedin.
She says babies start to remember when they are in their mothers' wombs.
Three-day-old newborns can recognise the sound of their mothers' voices and
respond to familiar passages which their mothers had read out repeatedly
during pregnancy.
But a baby's memory is extremely limited. Its brain weighs about 350g at
birth, and will grow to about four times that by age 18 to 21.
Most of the brain cells themselves are there from the start. The increase in
weight comes from a dramatic growth of connections between the cells - growth
which eventually slows but may never stop.
"People who continue to be mentally active continue to have positive
changes in the central nervous system throughout life," Dr Hayne says.
"Those who stop being mentally active have the exact opposite."
As links in the brain proliferate, infants slowly learn faster, remember
things longer, and retrieve memories more easily using a wider range of cues,
including language.
At two months, a baby can remember how to kick to move a mobile over its cot
if its foot is connected to the same mobile again a day later. But after two days
it will have forgotten all about it.
At three months, it can remember the mobile trick a week later.
At six months, it can remember for two weeks; at nine months, for six weeks;
at 12 months, for eight weeks; and at 18 months, for 13 weeks.
Given a more difficult task of recognising a face, a 2-year-old can remember
the face for up to a day; a 3-year-old for a week; and a 4-year-old for six
months.
"That's as long as we have tested them," Dr Hayne says.
Another experiment found that 2- and 3-year-old children who were taught to
use a "magic" machine that seemed to shrink their toys could not
describe the experience a year later using any words that they did not know
at the time.
Although they recognised things once they saw them again, the children could
not recall things verbally even if they had learned the right words in the
intervening year.
Dr Hayne and colleague Dr Gabrielle Simcock conclude that children's
inability to translate early experiences into words stopped them from
becoming a part of memory.
Older children can use language to help them remember things. But Dr Hayne
says there is no age after which we remember everything, even in adulthood.
"Most memories are lost because the brain only hangs on to things that
are useful to it," she says.
Our brain decides that something is worth remembering if we keep reinforcing
the memory.
"It's just a matter of frequency. You remember your mother's face
because it has significance to you and you have seen it a lot."
She says you can teach yourself to remember things such as people's names
through techniques such as paying attention when you are introduced and
rehearsing them later.
"I often do that trying to remember the names of the students in my
class. I have their photos and cover their names and practise attaching their
names to their photos."
Last year Dr Hayne signed a petition seeking a royal commission into the 1993
Christchurch Civic Creche case, in which childcare worker Peter Ellis was
convicted of sexual abuse based on the memories of preschoolers.
"Under optimal conditions, children can be highly accurate in their
ability to talk about the past and to recall abuse," she says. "The
bottom line is that you can't ask young children leading questions. That is
the first rule of interviewing children."
Memory aids
Memories are reinforced by use. If we don't use them, we lose them.
Most people forget early traumas, but children remember more if they grow up
in families that value memorising the past.
You can teach yourself to remember more by simple techniques such as paying
attention to things such as people's names and rehearsing them later.
Most of us could remember a lot more than we do. Feelings of memory
"overload" are due to stress caused by trying to process too much
too quickly.
Source: Professor Harlene Hayne
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