Children who cradle dolls on their left side show higher social cognitive abilities than those who do on the right, according to new research.
Scientists said the findings suggest children's cradling preference could help indicate some social developmental disorders.
The study builds on previous knowledge of a "left-cradling bias" - the phenomenon that humans will typically cradle a baby on their left side, enabling both parent and child to keep the other in their left visual field - which is unrelated to dominance of the use of the right or left hand.
Information from the left visual field is processed by the right hemisphere of the brain, which is associated with emotion and the perception of facial expression.
The research, led by Dr Gillian Forrester of Birkbeck, University of London and Dr Brenda Todd of City, University of London, was conducted with 98 typically developing children (54 girls and 44 boys) in reception or year one at a mainstream school in south London.
They were each given a doll to cradle and observed as to whether they held it more often in a left-cradling position.
It was found that those who showed this bias had a significantly higher social ability score compared with those who held the doll on the right.
The social ability traits tested included likeliness to follow rules, willingness to share with others and wanting to please their teachers.
As part of the study the children were also given a pillow to cradle, with three dots marked on to suggest a face. They were more likely to cradle this object on the left, which researchers said indicates deeply inbuilt facial recognition skills, as even a hint of a face will trigger the response.
By contrast, when given a plain pillow without a suggestion of a face, the children demonstrated neither a left nor right cradling bias.
Researchers said further investigation could help make important predictions about the trajectory of children's development based on their cradling responses, in association with social and communication abilities.
Dr Forrester said: "Even babies recognise the simple design of three dots surrounded by a circle as a face.
"The phenomenon, known as the 'left cradling bias', is not just present in humans - it is pervasive across the animal kingdom and found in species as different as gorillas and flying foxes.
"This left-visual-field bias is a natural ability, thought to have originated from a need to identify predators in the environment. In modern humans we believe that the left visual field bias for recognising faces and expressions supports our sophisticated social and emotional abilities.
"Keeping a baby in the carer's left visual field allows for more efficiently monitoring of the baby's wellbeing.
"Not surprisingly, the left cradling bias was also seen when children held a human baby doll, indicating that this behaviour is present early in development and you do not need to have had experience of holding babies to express this preference.
"What was interesting was that children who held the baby doll with a preference for the left arm scored higher on social ability tests, compared with children who held with a right-side preference, indicating that using the visual field linked to the dominant hemisphere for processing social stimuli gives the individual a real-life advantage."
The study is published in the journal Cortex.