Evening star., 1951-10-31
Left-Hunded in the Us.
Put at 1915 Million
Dr.. Rife Reports on Studies
Of Heredity and Environment
By Thomos R. Henry

There are between 10000 900 and
100000 left-handed persons in the
United States.
This is the estimate lately announced
through the American Association for
the Advancement of Science here, of
DR.. D. c. Rife, professor of genetics at
Ohio State College. who has been trying
to determine the relative effects Of
heredity and environment in producing
this condition. It often has been attrib-
uted solely to one or the other.
BY and large, he finds. the left-hand-
ers are sadly neglected group.
Most standard equipment" he says,
rs made for right-handers. Members
Of the military forces are trained to
shoot from the right shoulder, to aim
with the right eye. The chairs in most
school rooms are made for right-hand-
ers. Zippers on clothing, the arrange
ment Of violin strings and the design
OF grass Sickles afford familiar examples
OF conventional conformity to right
handed standards
Could Be Trained.
This would not be so bad, DR.. Rife
says, if it could be demonstrated that
being left-handed results from environ
ment, Then, with sufficient effort, left
handlers could be trained into right
handlers. Unfortunately the hereditary
element, which cannot be changed.
appears very large.
There is. he says. "a positive CORE
lation between the handedness of par-
ents and children. When both parents
are left-handed about half the children
are left-handed. When only one parent
is left-handed about one child in six
is left-handed When both parents are
right-handed only one child in 16 is
left-handed. These findings are what
might be expected if handedness is
hereditary, but they do not necessarily
prove it,
Nearly 20 per cent of identical twins,
he points out, show differences in hand
edneSs. Such twins come from the split
ting of single embryo. Hence they
have exactly the same heredity. 1t
might be assumed from such evidence
that handedness is entirely a matter Of
environment.
In this situation, Dr. Rife points out.
it is necessary to postulate Joint hered-
ity-environment effect. Many are born
right-handers or left-handers and there
is little to be done about it. On the
other hand many are born ambidextrous
able to use each hand with equal dex-
terity-or with only slight inclination
to favor one hand or the other. What
they become depends on early training,
or what adults they initiate in child
hood
This, he holds. explains the apparent
paradox of differences among identical
twins. The genes, which are the same
for both members of pair, result in
ambidexterity rather than handedness.
The latter then becomes matter Of en-
vironment. The hand preference can be
changed by training.
functional handedness, like the ma
jority of human variations" he says, "is
an end product of the interaction of
heredity and environment. Both are i'm
portant, and the relative part played by
each depends upon the individual. But
in view of the fact that heredity does
play an important part. left-handers
should be provided with facilities to ex-
press their natural preferences.
The thesis has been advanced In the
past that when efforts are made to
change left-hander to right-hander
there may be very unfortunate results,
such as stammering. This again, it is
held, depends on the individual. It would
only occur in persons with deep-seated
genetic tendency to favor one hand or
the other. This tendency would per.
meate the whole individual.