Hatchlings may
add, subtract
Results point to built-in
numerical understanding
By Susan Milius
Forget counting your chickens. They may
do it themselves. Chicks only 3 or 4 days
old manage an animal version of adding
and subtracting, says Rosa Rugani of the
University of Trento Center for Mind/
Brain Sciences in Rovereto, Italy.
R. RUGANI ET AL.
Inspired by experiments with human
babies, Rugani and her colleagues worked
out tests based on adding objects to and
taking them away from little piles hidden behind screens. With no special
math coaching, the chicks did a decent
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job of keeping track of object shifts representing such problems as 4 - 2 = 2 and
1 + 2 = 3, she and her colleagues report
online April 1 in Proceedings of the Royal
Society B.
“This is the first demonstration of
adding and subtracting in young animals” other than humans, Rugani says.
Other animals, including some primates
and dogs, have demonstrated numerical
powers as adults.
Karen Wynn of Yale University, who
has reported evidence of basic numerical
skills in human babies, says that the chicks
haven’t had a chance to learn or develop
much. “This work, then, is a compelling
existence proof that numerical understanding comprises a built-in system of
unlearned knowledge,” Wynn says.
Chicks tend to cluster, even with
experimental “chicks” that are actually
A chick stands amid objects and
screens used as tools in a test revealing
that chicks have a sense for arithmetic.
familiar little plastic balls. In one test,
each chick watched as a researcher first
hid balls behind each of two screens.
Then the tester let the chick see some of
the balls being moved from one screen
to the other. To go to the screen with
the larger number, the chick had to keep
track of addition and subtraction.
About 75 percent of the time, chicks
did it right, scuttling to the screen that
ended up with the most balls.
