By Janelle Weaver

Babies as young as seven months old may be able to take into account the thoughts and beliefs of other people, according to a paper published December 23 in Science. Called "theory of mind," this ability is central to human cooperation.

The finding provides evidence for the earliest awareness in infants so far of others' perspectives, says lead author Ágnes Kovács, a developmental psychologist at the Hungarian Academy of Sciences in Budapest. The research team made the discovery by measuring a simple behavior--how long infants stare at a scene--in experiments that did not require infants to explicitly assess others' thoughts or predict their actions.

Although many past studies have suggested that the ability to infer another person's viewpoint does not arise until the age of four, scientists demonstrated in 2005 and 2007, respectively, that 15- and 13-month-old infants can, in some situations, comprehend the beliefs of others.

Showing that younger babies possess this aptitude is significant, says developmental psychologist Rose Scott of the University of California, Merced. It's not known how babies acquire the capacity to understand others' mental states, but some scientists have argued that conversation has a key role. Because seven-month-olds have little experience with conversation--responding to voices and babbling rather than speaking words--Scott says that this study "really changes the kinds of theories that we're going to have to build for how these abilities develop."

Sensing expectation

The researchers showed 56 seven-month-old infants an animated cartoon in which a Smurf-like character watches a ball roll behind a rectangle placed on a table through a number of scenes. The ball either stopped behind the rectangle and was hidden from view, or kept rolling along the table until it disappeared from the scene.

In some of the scenes, the "Smurf" character watched the whole process. In others, he left too soon to see the ball's final position. For example, a ball that previously rolled behind the rectangle while the character was present would start rolling again and disappear from view after his departure. In the last scene, the rectangle dropped off, revealing no ball behind it.

The team found that the infants stared longer at the final scenes depicting a surprising outcome for the cartoon character when he retreated early (ball absent) than the anticipated one (ball present). Babies are thought to look longer at unexpected situations or events. So the researchers interpret the infants' behavior as indicating that they were surprised at the unexpected outcome, just as the cartoon character would have been. In other words, the babies seemed to process the character's viewpoint, not just their own.

Of two minds?

Although using looking times is a standard approach in the field, it is problematic because it is hard to know whether infants are attending to the right parts of the scene when they are looking at it, says developmental psychologist Alison Gopnik of the University of California, Berkeley. Tracking reaching behavior or eye movements will be necessary to substantiate the findings, she adds.

Gopnik also says that infants' responses could be explained by the perception of physical events, such as the sequence of ball movements, rather than the cartoon character's viewpoint. The researchers would have to add a control scene with no characters in it to show that they influence looking times, she says.

The authors did include experiments that were meant to account for alternative explanations, such as visual discrepancies between the movies. For example, the researchers made sure that the timing of the ball's movements and the total distance it covered was the same in all the movies. "I believe that we can be rather confident that the looking-time differences are really due to computing the cartoon character's beliefs, and not to some uninteresting differences between the conditions," says co-author Ansgar Endress, a cognitive psychologist at the Massachussetts Institute of Technology in Cambridge.

If confirmed by future studies, the results would indicate that infants are sensitive to social information and to what others see. But this does not necessarily mean that they have the ability to comprehend others' beliefs in the same way that four-year-olds do, Gopnik says. "The most interesting question now is how children revise and change their early view of the mind based on the evidence they see around them."