Evening star., 1937-09-04
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
BY THOMAS r. HENRY.

Far from being an invariably charac-
ter fixed by heredity human intelligence
is very notably. influenced by environ
ment.
Long a bone of contention among
psychologists and educators, this issue
has been subjected to crucial test by
a group of University of Chicago pro-
fessors-Dr. Horatio H. Newman, Dr.
Frank N Freeman and DR.. Karl J. Hol-
Finger.
The great difficulty in the past has
been that it has not been possible to
start comparisons either from the same
heredity or the same environment.
Brothers and sisters may have radically
different "heredities, due to different
combinations of the parental germs in
producing different individuals. Even
ordinary twins may differ markedly.
Only in the case of identical twins is
the heredity absolutely the same. Both
develope from single egg. Therefore,
everything dependent on heredity should
be identical for both. AS control group
the Chicago investigators selected 100
ordinary fraternal twins. Whatever diff
ferences developed between pair of
identical twins reared in different cir
cumstances could be attributed to the
environment.
Three comparisons were made in the
investigation. For identical twins reared
together there was correlation of 81,
almost perfect, on the Binet intelligence
test. For those reared apart this CORE
lation dropped to st. In other words,
environment produces an increased diff
ference of "a per cent in intelligence of
separated identical twins as compared
with the average difference between
identical twins reared together.
Results of three educational tests were
correlated with social differences in the
environment of the separated twins, and
the statistical average indicated that
cultural features in social environment
were also definitely effective in modify
ing the intelligence quotient. The in
creased difference of "a per cent is
ascribed statistically to various factors:
fifty per cent to educational differences
in the environment; 10 per cent to purely
social differences; II per cent to joint
social and educational differences; 9 per
cent to physical health differences, and
10 per cent to unknown causes. Much
of this 10 per cent is suspected to be due
to prenatal environmental influences. 1t
is known, for example, that identical
twins often injure one another IN the
womb in various ways as when one bOr-
rows more blood from the other than 1t
gives back.
In general, the three University Of
Chicago investigators found personality
traits seem to be much less predeter-
mined by heredity and more modified by
environment than is the intelligence quo
tient. Roughly, temperamental and emo
tional differences of identical twins
reared together seem to be 30 per cent
determined by heredity and 10 per cent
by environment.
Statistical analysis of these traits is
very difficult. Either the differences are
not measurable by the available tests, or
else the factors in the environment which
do produce such differences in PERSONAL
ity are not those Of formal education,
social position or physical advantages.
Because Of the inadequacy Of the statis-
tical data, the three professors give de-
tailed case histories of the identical twins
reared apart to provide a more definite
indication of temperamental differences.
Adopting the admittedly unscientific
principle, the investigators assume that
when differences in = certain trait are
found which might be expected from the
known environmental differences the re-
lation Is one of cause and effect.
One statistical correlation indicates
that the more education q person has
the more he inclines to be neurotic. Lit
tie Importance is attached to this indi-
cation, however, for = Is believed that