The findings demonstrated that infants, as young as eight-month-old, look for consistent patterns of behaviour and make judgements about people's preferences based on simple probabilities calculated from observed events and actions.
"Even before they can talk, babies are keeping close track of what's going on in front of them and looking for patterns of activity that may suggest preferences," said Lori Markson, Associate Professor at the Washington University in St. Louis.
"Make the same choice three or four times in a row, and babies as young as eight months come to view that consistent behaviour as a preference," Markson added.
For the study, detailed in the journal Infancy, the team conducted a series of experiments on a sample of 60 healthy, full-term infants with an even split of males and females ranging in age from seven to nine months and an average age of eight and a half months.
The researchers tracked whether infants, when asked to give a toy to the actor, would reach more often for the toy consistently chosen by the actor in previous trials, thus implying that the infant understood the actor's preference.
"Consistency seems to be an important factor for infants in helping them sort out what's happening in the world around them," Markson said.
"Our findings suggest that if a person does something different even a single time, it undoes the notion of someone having a clear preference and changes an infant's expectations for that individual's behaviour," Markson noted.