November 7, 2002
The eyes have it, for babies learning about the world
Adults often believe infants are off in their own world, but a new study indicates they are more tuned into the wider world and what the people around them are doing than previously thought.
The research by UW psychologists Rechele Brooks and Andrew Meltzoff reveals the importance of eyes to 12-, 14- and 18-month-old babies and shows that they are much more likely to look at an object when a person turns toward it with open eyes rather than closed. Not only that, but the study also shows that babies gazed at the object longer when the person looked at it with open eyes, and the babies initiated more vocalizing and pointing toward the object.
In addition, the study, published in the current issue of the journal Developmental Psychology, indicates that by the age of 14 months babies become sensitive to things that may obstruct another person’s view. The infants were more likely to look at an object when a person was wearing a headband rather than a blindfold that blocked the person’s view.
“Our work shows children are clued into the social world and are taking into account what other people are perceiving,” said Brooks, who is a research associate at the UW’s Center for Mind, Brain & Learning. “They are not off on their own, but are solving puzzles with the help of others. They are noting subtle differences and modifying their behavior.”
“This work is important because following another person’s line of sight is crucial for learning about language and understanding the emotions of other people,” said Meltzoff, co-director of the center and a UW psychology professor.
Brooks and Meltzoff refer to the behavior of a person looking where another has just looked as “gaze following,” and psychologists have known for some time that among adults detecting the direction of another’s glance is a crucial component of human social interactions. The concept of joint attention, or two people looking at and understanding that they are looking at the same object together, Brooks said, appears to be a “uniquely human quality.”
While other animals such as apes might engage in gaze following, she said, it appears they are “following the geometry of the head movement but not making inferences. The human difference is we are going down the road to making inferences. Babies go down this road because it is an integral part of their development. We are interested in knowing how this proceeds so we can work with parents and show them when their child can take in other people’s points of view.”
“Before about 1 year of age, babies either play with objects or they play with people, but they tend to do the two things separately,” added Meltzoff. “At about 12 months they begin a form of ‘baby multitasking.’ They now pay attention to both people and things simultaneously. In fact, they learn that paying attention to a part of you, your eyes, is the key to understanding more about the physical things in the world. Babies look back and forth between your eyes and objects.
“Eyes are a key to learning about the physical world and profiting from other people’s experience. By taking cues from others, babies can make good bets about whether certain objects are harmful, distasteful or deeply desirable. Another person’s eyes can tell you a lot,” he said.
To understand how gaze following develops, the UW researchers set up two experiments involving 96 youngsters in each investigation. There were 32 normally developing infants from each of the three age groups and an equal number of boys and girls.
The first experiment was designed to see if infants solely rely on head movements to direct their behavior, as some earlier research has indicated, or if they also read an adult’s eyes to see if they were open or closed when the adults turned towards an object. Equal numbers of boys and girls in the study were randomly assigned to eyes open or shut conditions.
Each infant was seated in a parent’s lap, across a small table from a researcher. Parents were instructed not to move their head or talk during the experiment. The researcher made eye contact with the child and engaged in warm-up play before placing two identical colorful toys on pedestals to the left and right of the table. Then the researcher resumed playing with the child at the table before starting four head-turning trials.
In the trials the researcher made eye contact with the infant before silently turning her head either toward the toy on the left or the one on the right. In the eyes open condition, the researcher kept her eyes open and shifted her gaze from the child to one of the toys for about seven seconds before turning back to the child. The procedure was the same in the eyes-closed condition, except the researcher shut her eyes before turning toward one of the toys and didn’t open them again until she was facing the baby.
The differences in the two conditions were striking. Ninety percent of the infants looked at the correct toy in the eyes open condition while just 46 percent looked at the correct toy when the experimenter closed her eyes before turning her head.
The children also were more interested in the toy when the experimenter kept her eyes open, looking at the toy slightly more than 50 percent longer than when her eyes were closed.
“In kids’ terms it’s as if the object suddenly becomes fascinating just because the adult is looking at it,” said Brooks, adding that the children also pointed and vocalized more in the eyes open condition.
Fifty-eight percent of the infants pointed at the correct toy when the experimenter’s eyes were open compared to just 17 percent when her eyes were shut. Similarly, 60 percent babbled and looked at the toy when the experimenter’s eyes were open while just 15 percent babbled when her eyes were shut.
“It is as if they are adding a comment that ‘we are talking about that object over there,’” said Brooks. “It is added emphasis from the children about a toy that isn’t that interesting when an adult’s eyes are closed.”
The second experiment was designed to see if infants would understand that a visual obstruction, in this case a blindfold, could block another person’s line of sight. The physical setup for this test was identical to the first except the experimenter used an opaque black cloth that she showed to each child and then tied around her head above the hairline. Half of the infants were exposed to a blindfold condition where the experimenter looked at the child and then lowered the cloth over her eyes turning toward one of the toys. The other half was exposed to a headband condition where the experimenter lowered the cloth to just above her eyebrows.
Once again more infants looked at the correct toy when the experimenter’s eyes were visible. Seventy-seven percent turned toward the same object in the headband test while 56 percent turned toward it in the blindfold test.
The researchers found a distinct age difference in the babies’ ability to distinguish a visual obstruction. The 12-month-olds had difficulty distinguishing between the headband and blindfold, while the 14- and 18-month-olds readily followed the eyes of the headband-wearing experimenter but rarely followed her when she turned with the blindfold in place.
“Clearly something is happening between 12 and 14 months, and at age 14 months kids can make a clear discrimination about uncovered and covered eyes,” said Brooks. “By 14 months they understand the blindfold is blocking another person’s view. It is amazing how sensitive infants are to their social partner. Infants show us that being there with closed eyes is not enough. Infants recognize when another person is perceptually available by, for example, having open eyes, to interact and respond appropriately.”
The research was funded by grants from the National Institute of Child Health and Human Development and by the Talaris Research Institute and the Apex Foundation, the family foundation created by Bruce and Jolene McCaw.