Categorization Distinction Between Obiects And Faces In17-Month-Old Infants

There are different kinds of words in human languages, including proper names and common nouns. A proper name refers to an object as an individual, whereas a common noun refers to an object as an interchangeable instance of a category. A basic puzzle in the study of early word learning is how infants identify a novel word’s lexical class and use the word to label its referent appropriately. According to a hypothesis named "narrow-and-broad" by Hall, infants assume words for some categories (e.g. people) label individuals and words for objects from other categories (e.g. artifacts) label instances of a category.The research in this dissertation tested the above hypothesis by using an intermodal preferential looking paradigm (IPLP). Under a tightly controlled experimental circumstances,17-month-old infants heard a novel word for a target artifact or person (a face) only four times, and their learning and categorization was assessed through three different test tasks. The target was presented with an out-categorical object in a mapping test and with an within-categorical object in a proper name test. To achieve a more rigid categorization, a third generalization test was designed in which the out-categorical object and the within-categorical object were paired together and infants were asked to find the target.In Experiment1, artifacts were used as test objects and objects from the same category were identical in shape but different in color. Infants showed preferential looking to the target in both mapping test and generalization test but no significant preference was found in the proper name test, providing evidence that infants can learn a novel word for a category based on the shape of artifacts. In Experiment2, infants heard a novel word for a female face and then were arranged to one of three categorization conditions with different kinds of within-categorical faces. Infants restricted the word to the target face only when the two faces were from different people but with similar external features, indicating that infants in this condition interpret words for people as proper names.Together, the findings reveal that infants interpret words for people and words for artifacts differently, specifically they extend words for people based on the internal features of faces and extend words for artifacts according to the objects’shape. Thus, the discrimination of a feature might play a role in categorization, and infants tend to use some characteristic with higher discrimination to decide whether two objects are from the same category.