SCIENCE
NEWS
This Week
A focus on children’s knowledge of
approximate quantities would enhance
arithmetic instruction, the researchers
propose. “The teachers in our school-based
study were skeptical about our experiments and surprised both by their students’ success and by their enjoyment of
the tasks,” Gilmore’s group concludes in
the May 31 Nature.
The team first tested 20 children, ages
5 to 6 years, from wealthy, highly educated families. Youngsters sat in front of
computers that displayed a series of
approximate-addition problems, each in
three parts.
One problem started with an image of a
girl’s face and a boy’s face in separate boxes,
with a bag marked “21” above the girl. A caption read “Sarah has 21 candies.” Next, the
kids saw an image showing another bag
marked “30” above the girl. Its caption read,
“She gets 30 more.” A final image displayed
a bag marked “34” above the boy. Its caption
read, “John has 34 candies. Who has more?”
Children answered nearly three-quarters
of such problems correctly. Guessing would
have yielded correct responses on only half
of the problems.
The researchers then presented similar
problems to 37 kindergartners from poor
and middle-class families. Children were
tested in a hallway outside their public
school classroom.
Although the setting offered more distractions than a laboratory, kids still
answered almost two-thirds of the problems correctly.
A final laboratory experiment tested
27 kindergartners from wealthy families on
two other approximate-math tasks. Subtraction problems appeared in the form:
“Sarah has 64 candies. She gives 13 of them
away. John has 34 candies. Who has more?”
Comparison problems used three boxes per
image, containing a girl and two boys, and
appeared in the form “Sarah has 51 candies.
Paul has 64 cookies. John has 34 candies.
Who has more candles, Sarah or John?”
Children correctly solved two-thirds of
the subtraction problems and 80 percent of
the comparison problems.
The new findings indicate that children
can exploit a neural system for estimating
quantities—which scientists have also
observed in a variety of nonhuman animals—to understand basic arithmetic,
remarks psychologist David C. Geary of the
University of Missouri–Columbia.
“This is the first study to demonstrate
that young children access this system when
SUM KIDS Approximate-arithmetic problems presented to 5- and 6-year-olds in a new study
included portrayals of addition (top row) and subtraction (bottom row), shown as a researcher
read descriptions of each image.
dealing with relatively complex addition
and subtraction problems,” says Geary, who
studies mathematical learning. —B. BOWER
Magnetic Logic
Electron spins could
do cool calculations
Engineers have proposed a new design for
circuits that could process information by
using electrons as tiny bar magnets. Such
circuits could someday become the building
blocks of a new generation of computers.
Computer-chip components called logic
gates output a 1 or 0 depending on the configuration of a gate’s inputs. In conventional
electronics, such bits of information are represented by electric voltages. Logic gates
contain semiconductor-based transistors
that switch states in response to those voltages. Such transistors, however, require thin
insulating layers that tend to leak electrons
and produce excess heat.
In addition to their electric charges, electrons carry a quantum mechanical property called spin. An electron’s spin generates
a magnetic field that can point in any direction. In recent years, several research teams
have built “spintronics” devices that encode
1s and 0s as spins pointing up or down.
Thus, the devices switch states by flipping
electron spin rather than changing voltages.
Such systems would reduce the overheating problems that afflict conventional
electronics. So far, though, researchers have
had to make spintronic gates out of multiple layers of metallic materials, in arrangements that would be difficult to link on a
chip, says Hanan Dery, an engineer at the
University of California, San Diego.
Dery and his colleagues now propose a
spintronic logic gate made mostly of semiconducting materials. The gate would be a
horizontal semiconducting bar with five
metallic contacts aligned on its surface.
Four of these contacts would act as the
inputs. Each of them could be magnetized
up or down, which would cause electrons
with up or down spins to move into the
semiconductor. An excess of spin-up electrons would lower the electrical resistance
at the boundary of the fifth contact. An
excess of spin-down electronic would not.
A separate circuit would receive the output, and current would flow only if the
resistance had decreased.
Dery’s team also describes in detail how
to link such components. Specialized circuits, also made of semiconducting components, would take the output current
from one logic gate, amplify it, and use it
to magnetize one of the input contacts of
another logic gate.
A main advantage of this design, Dery
says, is that present-day semiconductor-fabrication techniques could mass-produce
the devices. In principle, he adds, engineers
could pack these components onto a chip
up to 200 times as densely as they can pack
conventional gates onto a chip. His team
outlines the proposal in the May 31 Nature.
Paul Crowell of the University of Minnesota in Minneapolis says that the new
approach is elegant and original, but also
untested. “I really cannot say yet whether
it is going to be feasible,” he says. Laurens Molenkamp of the University of
Würzburg in Germany says that each of
the parts of the proposed device is “
relatively standard” but adds, “What I like
about this proposal is that it’s a full scheme”
describing how to link the components in
a new way. —D. CASTELVECCHI
GILMORE
