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Babies Size Up the Social Scene

Sizing up relationships between other people is key to success in human society. Whether your aim is navigating office politics or climbing the social ladder, you'd better know who's the chief and who's a pawn. A new study suggests that babies acquire this skill even before they learn to speak. In the 28 January issue of Science, researchers report that 10-month-old infants perceive social dominance and can predict who's likely to prevail when a conflict arises.

In the past decade, developmental psychologists have shown that babies are remarkably perceptive about the social world around them. Before the end of their first year, for example, infants understand that people sometimes have competing goals, and they take notice of whether one individual helps or hinders another.

In the new study, Lotte Thomsen, then a graduate student with Harvard University psychologist Susan Carey, and colleagues investigated whether infants also have expectations about who's most likely to get their way when two individuals have conflicting goals. They brought into the lab 144 infants between 8 months and 16 months old, accompanied by their mothers. Seated on mom's lap, each baby watched videos starring two crude cartoon figures—each essentially a block with an eye and a mouth (see video). (Psychologists often use simplified figures like these instead of more realistic ones to avoid confounding cues from facial expressions, gestures, or body posture.)

Blockbuster. Infants' responses to a video starring two animated blocks, suggests that they expect the larger block to dominate the smaller one.
Credit: Courtesy of Lotte Thomsen, Willem E. Frankenhuis, and Susan Carey

In one experiment, infants between 11 months and 16 months old watched a video in which a big blue block initially bounces across the screen from left to right. Next, a smaller green block crosses in the opposite direction. Then a conflict arises: Both blocks start across the screen and bump into each other in the middle, unable to pass. The standoff could end one of two ways, with either the blue or the green block tipping forward, as if bowing down, and receding into the background to allow the other block to pass.

When the little green block made way for the big blue block, infants looked at the screen for a few seconds after the clip ended before looking away. But when the little green block actually got its way, the infants stared at the screen for an additional 5 to 10 seconds on average. Thomsen and her colleagues, like many researchers who work with infants, interpret such extra attention as evidence that the infant has noticed that something is amiss—in this case, that their prediction that the large block should dominate the small block hasn't come true.

The researchers did several additional experiments to try to rule out alternative explanations, including the possibility that the infants were reacting to the size difference between the blocks instead of their perceived social relationship. When they removed the eyes and mouths from both blocks, the difference in looking time vanished, suggesting that infants' expectations about which block should prevail apply only to objects with human features.

In another series of experiments with younger infants, Thomsen and colleagues found that the difference in looking time emerges between 8 months and 10 months, suggesting that this is when the ability to detect social dominance comes online.

"This is the very first finding that demonstrates that preverbal infants pay attention to, and guess, the social relations between others on the basis of appearance," says Gergely Csibra, a developmental psychologist at the Central European University in Budapest.

Karen Wynn, a developmental cognitive scientist at Yale University agrees that the study adds a new dimension to previous work. "This fits very nicely with the broader theme of showing that it seems to be part of our inherent human makeup to be attuned to the social world [and] the meaning of interactions between other individuals," she says. "The asymmetry of power between individuals ... may be a fundamental social variable we are tuned to attend to."