At an early age, human infants can perceive social hierarchy and recognize physical size as a metric of social dominance, according to a study by psychology postdoctoral fellow Lotte Thomsen.

The study, released in an article in Science last week, found that animations of larger agents yielding to smaller ones attracted infants’ attention longer than animations of larger objects dominating smaller ones—an indication that infants were puzzled by the images of submissive larger agents.

Preverbal infants—ranging from about 8 to 13 months of age—were selected for this study as they were deemed too young to actively participate in dominance fights.

“American infants are unlikely to have watched small agents bow and prostrate in subordination to others of more formidable physical size, such as their parents,” the study said.

Noting that body size appears to be a nearly universal cue for dominance, the study observed that contestants in dominance fights typically assume postures that maximize their apparent size.

“Human infants face the formidable challenge of learning the structure of their social environment,” the study read.  “Previous research indicates that infants have early-developing representations of intentional agents, and of cooperative social interactions, that help meet that challenge.”

Through this study, Thomsen was able to discover that 10 to 13-month-old infants—but not 8-month-olds—recognize when two novel agents have conflicting goals, and that they use the agents’ relative size to predict the outcome of the dominance contests between them.

The study concluded that preverbal infants form representations of social hierarchy that mirror the generally accepted idea that larger sizes are dominant.

Thomsen—who works at the Laboratory for Developmental Studies—wrote her doctoral research on a related topic, “Seeing Social Relations.”

She wrote on her website that she is “interested in how elementary kinds of relational motives underpin meaningful psychological and social phenomena and intergroup relations.”

“I see this as a general psychological topic that relates to social, cognitive, evolutionary, and developmental psychology,” Thomsen wrote.

—Staff writer Rediet T. Abebe can be reached at rtesfaye@college.harvard.edu.