Last Thursday, Rebecca Saxe, a junior fellow of the Harvard Society of Fellows, gave a lecture on her recent studies of infant cognition entitled “Secret Agents: Infants’ Inferences About Hidden Causes.” In her lecture, sponsored by the psychology department, Saxe argued that an infant’s ability to infer the hidden causes of ambiguous interactions may be more sophisticated than previously thought.
“I wasn’t originally interested in causal reasoning,” Saxe said. “The field I specialize in is neuro-imaging, which studies whether distinct brain regions in a human adult are recruited just when the person must use attributed beliefs to reason about someone else’s action.”
In order to demonstrate this, her research team conducted a number of experiments on infants from eight to twelve months old, presenting them with a combination of different scenarios.
In one scenario, infants were set in front of a small stage, with the researchers hidden behind it, so that the infants were given no reason to believe that anyone else was present in the room. Next, a beanbag was tossed onto the stage from either the left or the right side, making certain the infants still could not see its source of origin. From this point on, the researchers showed the infants that a human hand was behind one side of the screen, and a toy train on the other. Then, the beanbag was thrown again from one of the sides. Their prediction was that the infants would look longer, indicating their surprise, if the second toss of the beanbag came from the side that they knew the train was behind.
On the whole, their predictions were correct. It seemed that infants use the position of a hand, or simply their working knowledge of the mechanical abilities of a hand, to infer that it would be the more likely “invisible agent” to throw the beanbag than a toy train.
“My studies have led to a number of fundamental questions,” Saxe said. “Namely, do humans have special mechanisms designed by evolution for recognizing and reasoning about other minds, or does social cognition share the general-purpose machinery we use for recognizing chairs or reasoning about falling apples?”
Saxe said it was her quest to answer questions like this that led her to experiments on infants. In addition to raising the basic questions of the brain’s fundamental mechanisms, Saxe said that social cognition provides an important case study for the deepest question of cognitive science: How are concepts and beliefs formed, stored and deployed in the human mind and brain?
“The causal reasoning of infants is the earliest stages of social cognition and perception,” she said.
According to Saxe, children make a similar transition from the first stage of reasoning about human behavior, based mainly on goals or desires, to the richer second stage, based on both desires and beliefs. Children acquire the idea that people have beliefs about the world, that some of the beliefs are false, and that different people have different beliefs about the same world.
Saxe concluded that we seem to be equipped by evolution with a special mental mechanism—a special faculty or module in our minds—dedicated to understanding why people do the things they do.
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