Mutual Exclusivity: How Children Learn the Meanings of Words

Given two objects, each child responding at random would have a 50% chance of grabbing the unfamiliar object first. However, if the child knows the label of the familiar object and treats it as being exclusive to that object, then they should guess that the new label refers to the unfamiliar object (Figure 1). Because 2-year-olds have different experiences, not every child knows or remembers the label for the banana. So some toddlers select the banana, but most link the unfamiliar object to the novel label. In order to have enough power to see significant results, researchers would have to test at least 18 children. 

Figure 1: Pie chart showing the percent of children who selected the unfamiliar object.

The world is full of objects, and one of the early challenges faced by children who are learning a language is to match the labels they hear to the correct objects in their environment. Children have several tendencies that help them to solve this problem. First, they treat labels as referring to whole objects, so they don’t get confused about what is being labeled. For example, when a child hears “banana,” they don’t think the label is a feature of the object, like a part or a color; they assume the word refers to the whole object. Second, children treat these labels as being exclusive. So, each object has only one name. Thus, if they hear a new label, they can assume it does not apply to any of the many items they’ve already learned to name. Since children learn words very effectively during this time in their development, they quickly reduce the ambiguity in their environment, and the problem of linking labels to objects becomes increasingly easy to solve using the principle of mutual exclusivity.

The finding that children can determine the meaning of a new word without having to receive direct instruction from another person is important, because it shows that parents and other adults do not have to make a special effort to teach their child language. Instead, just by speaking naturally and introducing the child to a wide range of objects and experiences, adults are actually enabling the child to learn new vocabulary.