One-year-old babies may not be able to talk, but they may think logically, according to new research that shows the oldest known basis for our ability to reason.
Legendary psychologist Jean Piaget believed that we did not have logical reasoning skills until we were seven years old, but scientists scanned the eyes of 48 babies and discovered that they are able to reason through the elimination process. The research was published today in the journal Science.
The type of reasoning in question, the process of elimination, is formally called "disjunctive syllogism." It is like this: if only A or B can be true, and A is false, then B must be true. So, if the cup is red or blue, and it is not red, then it is blue. The process of elimination is not necessarily the easiest form of reasoning, says Justin Halberda, a psychologist and child development expert at Johns Hopkins University who was not involved in the study today, but is crucial to higher thinking. "One of the central pieces that separates human reasoning from all other forms is to deny a premise: you see that if it is not A, it is something else," he says. "That's something pretty elegant."
In today's study, the babies observed small animations. They saw two different objects, like a flower and a dinosaur, and then both hid behind a barrier. An animated glass removes one of the animations, like the flower. Then, the barrier goes away. Either the flower remains (as would be the case), or the dinosaur, strangely, is still there.
By tracking the movements of the babies' eyes, the scientists discovered that the babies watched more closely when the dinosaur was still nearby, indicating that they were confused. (Researchers who work with babies who can not talk often measure how long they watch something to see if they are surprised or interested).
On a practical level, additional research in this area could be used as a means to diagnose cognitive disability. For example, doctors could track babies' eyes and see if they were looking for the typical pattern for someone their age, says Halberda. But most important, he says, is that this research will open the door to more work on how younger babies think and reason. "It's about launching a whole body of work that will emerge in the next decade," says Halberda. "It's an invitation".