Source: Laboratories of Nicholaus Noles and Judith Danovitch—University of Louisville

Humans are different from other animals in many ways, but perhaps the most important differentiating factor is their ability to use language. Other animals can communicate and even understand and use language in limited ways, but trying to teach human language to a chimp or a dog takes a great deal of time and effort. In contrast, young humans acquire their native language easily, and they learn linguistic rules without explicit instruction, which is an accomplishment that even the smartest animals cannot match. 

One advantage young humans have over animals is that the human brain is especially adapted to learn new words. With only a few exposures, young children can learn new words and remember them. Perhaps more impressively, children can use what they already know to guide their future learning. For example, children treat objects as if they have only one label. So, if a child has learned the word hammer, they won’t assume an unfamiliar tool has the same name. This is the principle of mutual exclusivity.^1-2

This video demonstrates children’s ability to use mutual exclusivity to match words to objects in their environment.

Recruit healthy 2-year-old children with normal hearing and vision and no history of developmental disorders. For the purposes of this demonstration, only one child is tested. Larger sample sizes are recommended when conducting any experiments.

1. Gather the necessary materials.

1. Select a familiar and unfamiliar test object.
   1. The familiar test object should be something identifiable to most 2-year-olds. In this case, use a toy banana.
   2. The unfamiliar test object

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 lab

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

1. Markman, E.M., & Wachtel, G.F. Children’s use of mutual exclusivity to constrain the meanings of words. Cognitive Psychology. 20, 121-157 (1988).
2. Merriman, W.E., & Bowman, L.L. The mutual exclusivity bias in children’s word learning. Mongraphs of the Society for Research in Child Development. 54 (Serial Nos. 3-4) (1989).