Even in the cradle, babies as young as 5 months have a rudimentary ability to add and subtract, according to a study being published today.
The study seems to show that infants know when simple calculations like one plus one are done correctly or incorrectly. The infants indicated awareness that a wrong answer was given by staring longer at the unexpected results.
Researchers say they believe that the finding, combined with corroborating research on infants and animals, indicates that, however modest, humans have an innate, biologically determined propensity for learning mathematics, as has been proposed for language.
Of more immediate interest to parents, the research sheds new light on the moment when a baby first learns to count.
The new finding was reported in the journal Nature by Dr. Karen Wynn, a developmental psychologist at the University of Arizona. But some experts disagreed with her findings. "This study doesn't necessarily show the infants understand math," said Dr. Patricia Bauer, a psychologist at the University of Minnesota. "It could simply mean they understand that the display had changed in a way that violated an expectation, but not that they understood the change in quantity."
Dr. Wynn employed a well-established and widely used method for measuring whether infants find an event unexpected or not: Babies will stare longer at something that is surprising.
To present the babies with math problems, Dr. Wynn used 4-inch-high figurines of Mickey Mouse. For example, for the problem one plus one, she showed the infants one figurine, then put up a small screen that hid it. Then, in full view of the infant, a hand placed another figurine behind the screen.
Finally, the screen was pulled away to reveal both figurines. Video monitors recorded how long the baby looked at the two Mickey Mouse figurines.
Using the same procedure, the researchers would sometimes pull the screen away to reveal a false answer, for example, only one figurine, when there should have been two.
In these cases, the infants gazed for several seconds longer, indicating that they had anticipated the correct answer and were surprised by the different number.