New research demonstrates that infants as young as eight months old understand that if an object is moving and appears to be in control of its movements, then it's got something inside it that's helping it to move.
A study recently published in Proceedings of the National Academy of Sciences lends additional credence to the theory that babies are born with certain expectations — physical, psychological, and, it turns out, biological — of how the world works. University of Illinois researchers gave a group of eight-month-olds a set of objects with different characteristics: Some could move on their own, some could respond to changes in the environment, some could do both, and some could do neither. When the babies were shown the insides of the objects, they stared longest at the ones that were both self-propelled and self-acting. Lead researcher Renee Baillargeon says this indicates that the infants’ expectations were violated in that “they categorize [this type of object] as an animal, and they assume it has insides.”
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One explanation for this behavior can be tied to the evolution of humans’ cognitive systems in order to survive, says Baillargeon: “Understanding that animals are capable of both self-propulsion and agency would have greatly helped our human ancestors to evade predators and to capture prey…A predator whose insides have been removed is no longer a threat. And of course, eating the insides of a predator or prey provides nutritious food.”