Study shows when infants begin to infer intentions

One-year-old infants have the ability to understand the intentions of relatively complicated actions performed by adults around them, University researchers have discovered.

“This is the first evidence that infants make inferences about a person’s underlying intentions based on observing him or her completing a series of actions,” said Amanda Woodward, Assistant Professor in Psychology. “In particular, we found that 12-month-olds understand that the meaning of a particular behavior depends on the other behaviors of the person,” added Woodward, co-author of the article “Twelve-Month-Old Infants Interpret Action in Context,” which has been published in the current issue of the journal Psychological Science.

Prior to Woodward’s experiments, scholars had not known how early this ability develops. According to Elizabeth Spelke, professor of brain and cognitive sciences at MIT, much of children’s cognitive development occurs during ages 3 through 6 and has been investigated in detail over the last 15 years through studies of preschoolers. “Because the tools for investigating developing ‘theory of mind’ in preschool children typically rely on language and structured tasks, it has proven more difficult to investigate the earlier development of children’s understanding of actions. Here is where Amanda Woodward has made her greatest contributions.”

Adults understand that the significance of a particular action depends on the context in which it occurs. For example, a parent might pick up a bottle in order to take it away, or they might pick up the bottle in order to fill it with juice and return it to the baby. Woodward’s research demonstrates that 12-month-old infants, like adults, interpret a particular action differently depending on the other actions the person performs. This new finding comes a year after Woodward published research that indicates younger babies can understand isolated actions, such as grasping an object, as being intentional.

Now researchers know that by the time babies are 1 year old, they begin to complete their thought processes and make the additional steps necessary to comprehend that a person not only means to grasp an object when he or she reaches for it, but also intends to complete a different action.

“Learning to reason as an adult is a complicated skill,” Woodward said. “What we are doing is taking the skill apart and learning at which points different parts of adult reasoning begin.”

The current finding is important because it points to a source of rapid learning in children, who typically begin to talk, walk and imitate adult actions with growing skill between ages 1 and 2.

“One of the most critical developmental achievements is coming to understand the intentions behind other people’s actions. This ability is the basis for many kinds of learning in toddlers and young children, for example, acquiring language, learning socially appropriate behaviors and learning how to use objects as diverse as containers, door knobs and VCRs,” Woodward explained.

“Our research shows that children don’t necessarily need to be explicitly taught how to do these things. They can make inferences about the significance of an action just by observing other people,” she added.

“The ability to link actions that occur together provides infants with a powerful tool for making sense of human behavior,” Woodward writes in the paper co-authored by Jessica Sommerville, a graduate student in psychology.

For the experiment, the researchers began by showing babies an ambiguous event: an experimenter reached toward and touched the lid of a clear, plastic box containing a small toy. Babies were not sure whether the experimenter’s intention was to touch the box or to obtain the toy within the box. Next, the researchers showed babies this ambiguous action, followed by another action—the experimenter opened the box and grasped the toy.

Having observed the sequence, when babies again saw the ambiguous action made on its own, they understood it to be directed at the toy, not the box. That is, the infants inferred the intention behind this ambiguous action based on the other actions the experimenter had performed.

To measure infants’ reasoning skills, Woodward and Sommerville studied infants’ patterns of visual attention. This method is very useful with infants who cannot yet talk. When infants see the same event again and again, they look at it less and less. Then, if there is a change in the event and infants notice it, they will look longer. In the experiments, babies first saw an actor touch a box containing a particular toy. When they were bored with the event, the actor touched a new box that contained the same toy or touched the same box, which now contained a new toy.

The babies looked longer when there was a change in the toy rather than when there was a change in the box. This suggests they understood the action as directed at the toy and not the box. Altogether, 60 12-month-old infants participated in the experiment.

Woodward is among a group of researchers with the University’s Early Childhood Initiative, which the Robert R. McCormick Tribune Foundation funds. The McCormick Tribune Foundation, the John Merck Fund and the National Institutes of Health supported Woodward and Somerville’s work on infant ability to interpret actions.