Evening star., 1936-12-29

ATLANTIC CITY, December 28.-An
electrical brain that corrects examina-
ton papers and computes the students
marks with uncanny speed and accuracy
was reported to the American Associa-
ton for the Advancement of Science here
today by Dr. Ben D. Wood of Columbia
University.
The mechanism. DR.. Wood said.
actually senses" an error. 1t is based
essentially on the fact that lead pencil
mark on paper will conduct weak cur
rent of electricity. 1t can correct and
compute the score of test containing
as many as 375 questions instantly, every
operation being simultaneous.
It is essential that every question In
the test be answered by making pencil
mark, according to pre-arranged code.
at definite place on the test sheet. II
the mark is made in one place the answer
is correct, and if it is made in another
place the answer is wrong.
Then a metallic plate with $50 sets OF
electrodes is laid upon the test sheet
one set of electrodes corresponding 10
every possible right or wrong answer.
Whenever pair of these electrodes rest
upon pencil mark an electrical circuit
is closed and a weak current flows. Where
there is no pencil mark the gap remains
open.
The machine knows the answer. Each
electrode has been connected with
master answer sheet punched SO That IL
automatically divides the contact units
into two groups-the rights and the
wrongs 1t splits the incoming electrical
impulses into two circuits one carrying
the aggregate of currents from the cor
rect answers and the other carrying the
aggregate from the wrong answers. Thus
the strength of the currents set up by
the right answers is an exact multiple OF
the single unit of current carried through
a pencil mark. 1t is the same with the
wrong answers. The balance Of the two
aggregate currents is the score.
With another adjustment 1t Is pos
sible to score papers with as many as four
possibilities of wrong answers to one OF
the right answer. The great dimculty
which had to be overcome in perfecting
the device was to work out a method by
which exactly the same current would be
carried through pencil mark. regard
less of how light or heavy 1t was made
by the pupil.
The machine, it was pointed out by
DR.. Wood, should prove OF great advan-
tage in correcting the examination
papers of large classes. 1t does away
with a large amount Of irksome labor
and at the same time is far more accur-
ate than the professor himself or his
students could be. 1t also makes possible
tests of large blocks Of the population.
such as all the high school children OF a
State. 1t is also of great promise for
making up year grades for students
which. under present rating systems,
often is extremely complicated.
He cited this example: The term mark
of a student must be calculated from
his marks on 10 weekly quizzes each with
a weight of three, three monthly quizzes
each weighted six, four themes each
weighted IA, two sepcial theses each
weighted 20, and two written examina-
tions each rated II. There are 100 STU
dents in the class. To make up the
grades 21 two-digit numbers must be
multiplied by weights varying from three
to 20, the products added. and the SUM
divided by 168-and this must be re.
peated 100 times. The machine per-
forms all these computations for each
student almost instantaneously.
In its special, limited field it works
very much like an actaal brain. The