Even babies seem to know who is boss, according to new research that suggests infants use size as a measure to predict who will prevail when two individuals have a conflict.
Scientists from Harvard University and the University of California, Los Angeles, conducted five experiments on 144 infants ranging from eight months to 16 months old, gauging their reactions to videos of interactions between cartoon figures of various sizes.
When a larger figure yielded to a smaller one - an unexpected outcome - the babies watched much longer, an average of 20 seconds compared to 12 seconds, study author Lotte Thomsen said. Previous studies indicated that infants tend to watch something longer when it surprises them.
These reactions suggest people are either born with - or develop at a very early age - some understanding about social dominance and how it relates to comparative size, an association found in human and animal cultures alike, Thomsen said.
Babies make sense of the world
"To us, this is one of many studies that suggests that babies come into the world with a quite sophisticated set of basic conceptual building blocks that they use to make sense of the world and learn about it," said Thomsen, a research fellow in Harvard's department of psychology and an assistant professor of psychology at the University of Copenhagen.
"Learning this is crucial to get along in the social world humans create together and - ultimately - crucial for surviving and prospering and having healthy offspring," she added. "So, it would be possible for evolution to pre-programme us in ways that help us discover the kinds of social relationships that surround us."
The study is reported in the journal Science.
The videos used in the research depicted a large and small block with eyes and a mouth bouncing across a stage in opposite directions. Infants watched the two blocks meet in the middle, impeding one another's progress. They then saw either the large or the small block bow and step aside, deferring to the other.
The babies' reactions indicated that eight-month-olds failed to grasp the significance of the larger block deferring to the smaller one, the study said. But those aged 10 months to 16 months consistently demonstrated surprise at depictions of the larger yielding to the smaller, suggesting this conceptual understanding develops between eight and 10 months of age.
Thomsen noted that the animal world is rife with examples of size-related dominance, such as birds and cats that puff up to look physically larger to adversaries, or dogs that prostrate themselves to demonstrate submission.
Children and social ranking
"Bigger animals tend to be more dominant, and being dominant and having priority to get the lion's share of resources may make each individual even bigger," Thomsen said. "Interestingly, it also goes together in human languages and cultural practices. We speak and think about a 'big' leader . . . or the 'little' man on the street that is getting 'stepped on.' We also prostrate or bow to show respect to gods and superiors."
George Hollich, an infant researcher and an associate professor of developmental psychology at Purdue University, said the new study adds to the understanding of infants by suggesting they may be aware of social rank based on size alone.
Does this mean babies feel their larger parent is dominant?
"It means they might start out with that bias," Hollich said. "I think they're sort of learning this somewhere in their environment. If the smaller parent is always in charge, they'll see that after awhile."
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