Baby Got Math: Seven-month-olds Show An
Abstract Numerical Sense Before They Can Even Talk
February 13, 2006. Source
Duke University
Durham, N.C. -- Cognitive
neuroscientists have shown that babies have an abstract numerical
sense, as demonstrated by their ability to match the number of
voices they hear to the number of faces they expect to see. This
numerical perception across senses demonstrates that babies have a
truly abstract sense of numerical concepts -- and not just one that
is a function of a particular sense -- even before they learn to
speak. Previous experiments on this topic have yielded conflicting
and equivocal results, said the researchers.
The researchers, Kerry Jordan and
Elizabeth Brannon of Duke University, published their findings the
week of Feb. 13-17, 2006, in the Proceedings of the National Academy
of Sciences. Jordan is a graduate student and Brannon is an
assistant professor in Duke’s Center for Cognitive Neuroscience and
Department of Psychological and Brain Sciences. The research was
sponsored by The National Institute of Mental Health, The National
Science Foundation and the John Merck Fund.
In their study, Jordan and Brannon used the same basic experimental
design that they had previously used to demonstrate that monkeys
show numerical perception across senses. In those experiments, the
researchers, collaborating with colleagues at the Max Planck
Society, presented the monkeys with the sound of two or three
animals making a natural “coo” sound. At the same time they gave the
monkeys a choice to look at video images of either two or three
monkeys cooing. The researchers found that the monkeys
overwhelmingly chose to look at video images that matched the number
of monkeys they were hearing.
Similarly, in the study with seven-month-old infants, the Duke
researchers presented the babies with the voices of two or three
women saying “look.” Simultaneously, the babies could choose between
looking at video images of two or three women saying the word. As
they had found with the monkeys, the researchers found that the
babies spent significantly more time looking at the video image that
matched the number of women talking. According to Brannon, similar
experiments by other researchers had not shown definitive results
because of problems in their design.
“First of all, they had used arbitrary stimuli such as a number of
objects or sounds like drumbeats, rather than ecologically relevant
stimuli. We don’t know for sure this was a problem but it seems
likely” said Brannon. “Also, those experiments presented the sounds
successively and so the duration of the sound sequence was a
potential problem.” Finally, said Brannon, previous experiments used
the same subjects for multiple trials, which meant that the subjects
could have learned to associate such non-numerical factors as the
length of a sequence of drumbeats or the intensity of sound with
numerical size. In contrast, Jordan and Brannon gave each baby only
a single trial, so that the babies had no opportunity to learn
anything about the stimuli.
“As a result of our experiments, we conclude that the babies are
showing an internal representation of ‘two-ness’ or ‘three-ness’
that is separate from sensory modalities and, thus, reflects an
abstract internal process,” said Brannon. “These results support the
idea that there is a shared system between preverbal infants and
nonverbal animals for representing numbers.”
The researchers said that further studies will test both babies and
monkeys on their perception of larger numbers, to further explore
the details of their numerical abilities. They will also explore
whether monkeys can explicitly match the number of a sequence of
sounds and a number of objects using a touch screen task in which a
monkey has to choose between two visual arrays. Such experiments,
they said, will help determine the psychological importance of where
monkeys and babies look in their numerical matching paradigm.
Such studies have broad implications for understanding the
evolutionary origins of numerical ability and how that ability has
developed in humans, they said.
For more information, contact: Dennis Meredith | (919) 681-8054 |
dennis.meredith@duke.edu
|