There is a lot going on in the heads of babies - probably more than most people think, says Texas A&M University psychologist Teresa Wilcox, who studies the way babies think about and interact with their physical world. She's examining how and when babies begin learning about objects they encounter.
According to her research, there's a clear hierarchy in the kinds of information babies use to "individuate" objects. Object individuation, she says, refers to a baby's ability to recognize an object based on a mental picture the baby forms using the object's characteristics and features. As babies build these mental pictures, they tend to pay attention to certain features more than others, depending on the age of the baby.
"Individuation is important in learning," Wilcox explains, "because it allows us to make predictions about an object based on past interactions with that object. How babies individuate objects tells us a lot about how they perceive their world. If they don't individuate objects, that means every experience with an object is a new experience."
In order to recognize an object, Wilcox says babies, like the rest of us, rely on a mental representation of that object. At 4.5 months, babies pay particular attention to features like shape and size, but they don't individuate objects, she says.
By 5.5 months, they begin to individuate objects, but they don't bind specific features to those objects, she notes. This occurrence, she explains, is similar to the way a person passes a wreck while driving and sometimes can recall the number of automobiles involved but not the color and models of those automobiles.
Though they first show the ability to start individuating objects at 5.5 months, babies don't bind specific features to objects until 7.5 months, Wilcox explains. At this time, they also begin using patterns in their mental representations of objects, and at 11.5 months, color becomes important to them in this process.
Up to this point, she explains, color is a part of a baby's world, but a baby doesn't use it to draw conclusions about whether the object in front of him or her is the same object or a different object.
"It's very intriguing," Wilcox says, "because babies can distinguish between colors. They can discriminate against colors and categorize colors - they use color, but they don't use it to individuate objects."
Wilcox believes that this information hierarchy is related to an information processing bias that's innate in babies. She says form features, like shape and size are deeply embedded in the physical world and that they are important for making judgments about the outcome of physical events. Babies, she notes, draw on these early in life to keep track of the identity of objects.
On the other hand, surface features like color and pattern are not thought of as being stable, enduring properties and aren't as important for reasoning out physical events, she says.
"Babies tend not to attach these sorts of features to objects early in their development, and it may have to with the fact that form features are just not as important for reasoning out the physical world," Wilcox says. "So an object's color, its pattern or its luminance doesn't have that much bearing on whether the object can fit into a container, whether it can be supported on a ledge without falling or whether it can become occluded or not."