​Infant Categorization Development 

What have we learned about babies’ categories?

​Imagine how hard it would be to think about every dog you encountered as a separate individual—without recognizing that all dogs have some features in common. By grouping dogs together, we know that we can call them all using the same label (dog), that they can eat the same food, and that they might jump up when excited. Categories, such as dog, shoe, and cup, are especially important for babies. As infants learn about and remember objects, grouping those objects will help them learn the objects’ names, what to do with those objects, and how the objects will react. We have discovered babies have amazing abilities to group objects. By 4 months, babies can group dogs together and recognize that a cat is not the same sort of thing as a dog. This is remarkable when you consider that at 4 months babies don’t know the words “dog” or “cat”, and that dogs and cat are very similar—they have four legs, tails, fur, etc. It might be tempting to say that babies “know” the category of cat or dog by 4 months. However, babies only notice such categories under some circumstances. For example, younger infants group together dogs that look alike, but not dogs that look more different from one another. In addition, young babies are more likely to form a group of “dog” if they see different dogs together than if they see those dogs one at a time—probably because they can compare the dogs and see how they are similar and different without having to remember one of them. This kind of research is important for making sense of how infants organize and remember the objects they encounter—which is important for uncovering the origins of language and conceptual understanding.

Four- to 6-month-old infants presented with two pictures of different items form more exclusive categories (e.g., a category of dog that does not include cats). Infants presented with two identical pictures form more general categories (e.g., one that includes both dogs and cats). Infants appear to have difficulty noticing how objects are similar when objects are presented one at a time.

Older infants (10 to 13 months of age) also form more exclusive categories when presented with actual objects to play with when they are given two different objects at one time. When given two identical items at one time, infants form more general categories.