Infants Expect Animals to Have Guts

New evidence published in the journal Proceedings of the National Academy of Sciences helps support the idea that babies are born with core psychological and physical frameworks that help them navigate the world.

University of Illinois Psychologist Renée Baillargeon, who conducted the research with graduate student Peipei Setoh, contend that 8-month-old infants expect objects they identify as animals to have insides.

The researchers contend that when babies see a self-propelled object, their psychological framework allows them to subconsciously understand that the object has internal energy. Furthermore, the researchers contend, when a baby sees that an object has control over its own actions -- something that responds to changes in its environment -- their core framework leads them to view the object as an agent that has mental states.

Young children expect animals to have different insides from inanimate objects, and they realize that an animal's insides are important for its survival," Setoh said. "They know that if you remove the insides, the animal can't function."

Baillargeon said the babies "seem to be born with abstract expectations that drive their reasoning."

The researchers devised an experiment to test whether babies understand that animals have insides by employing the violation-of-expectation method, where in a baby will gaze at something longer is something unexpected happens.

First, the researchers familiarized the babies with a set of objects, some of which appeared agentive or self-propelled, or both, while others appeared to be neither.

The researchers then tested the babies' exceptions by revealing that the objects were hollow. The infants looked longer at the hollow objects only if they were previously shown to be both self-propelled and agentive, which Baillargeon said violates the infants' expectations.

"When babies encounter a novel object that is both self-propelled and agentive, they categorize it as an animal, and they assume it has insides," Baillargeon said. "It cannot be hollow."

In a follow up experiment, the researchers capitalized on the fact that by eight months, most babies have learned to associate fur with an object that might be an animal. When the babies were shown a novel, self-propelled object covered in beaver fur, the babies seemingly identified it as an animal and expected it to have insides, showing surprise by staring at the object longer when it was revealed to be hollow.

"These findings go against previous claims that babies have no core understanding of biology," Baillargeon said. "Now that we have shown babies expect totally novel animals to have insides, it calls these claims into question."

Another explanation for the infants' reactions is that they are tied to a human cognitive system that evolved to deal with animals as a food source.

"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," Baillargeon said. "And insides would have played a critical role in their interactions with all animals. 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."