Research indicates that subtle grammatical hints in sentences help young children understand the meanings of new words.
How do young children expand their vocabulary? Studies show that even infants as young as 1 year old perceive new words as having different meanings from the ones they already know. However, the reasons behind this phenomenon have puzzled scholars for the last 40 years.
Recent research from the MIT Language Acquisition Lab sheds new light on this topic. It reveals that sentences carry subtle grammatical cues that assist young children in deciphering the meanings of unfamiliar words. This study, involving 2-year-olds, highlights that even toddlers can pick up on grammatical hints in language and use this information to learn new vocabulary.
“Children, even at a very young age, possess advanced knowledge of sentence grammar, which they can utilize to understand new words,” explains Athulya Aravind, an associate professor of linguistics at MIT.
This new perspective challenges the earlier theory that children lean on the principle of “mutual exclusivity,” which suggests they assume each new word matches a unique object or category. Instead, this research shows that children significantly respond to grammatical details when making sense of words.
“This discovery is thrilling because it presents a straightforward idea that clarifies so much about children’s language understanding,” states Gabor Brody, a postdoc at Brown University and the paper’s lead author.
The paper, titled “Why Do Children Think Words Are Mutually Exclusive?” is available in advance online in Psychological Science. The authors include Brody; Roman Feiman, the Thomas J. and Alice M. Tisch Assistant Professor of Cognitive and Psychological Sciences and Linguistics at Brown; and Aravind, who is the Alfred Henry and Jean Morrison Hayes Career Development Associate Professor in MIT’s Department of Linguistics and Philosophy.
Understanding Focus
Many researchers believed that when learning new words, children have an inherent bias towards mutual exclusivity, which could help explain their vocabulary acquisition. However, this concept has never been definitive: several words, such as “bat,” can refer to various objects, and many objects can be described using numerous words. For instance, a rabbit might be called a “rabbit,” a “bunny,” an “animal,” or even a “delicacy,” depending on the context. Despite these complexities, the idea of mutual exclusivity has been considered a strong tendency in how children learn words.
Aravind, Brody, and Feiman argue that children do not possess any inherent bias towards mutual exclusivity. Instead, they utilize “focus” cues to interpret the meanings of new words. In linguistics, “focus” refers to the emphasis on certain words to indicate a contrast. Depending on which part of the sentence is stressed, the same sentence can convey different meanings. For example, “Carlos gave Lewis a Ferrari” suggests a contrast with other potential cars he could have given. In contrast, “Carlos gave Lewis a Ferrari” indicates a contrast with other recipients — he might have given Alexandra a Ferrari.
The researchers conducted three experiments with a total of 106 children to manipulate focus. The kids watched videos of a cartoon fox requesting them to point at various objects.
The initial experiment demonstrated how focus affects children’s choice between two items when they hear a label, such as “toy,” which could apply to either. After the fox named one of the items (“Look, I’m pointing to the blicket”), it told the child, “Now you point to the toy!” The children were split into two groups, with one group hearing “toy” without emphasis and the other with emphasis.
In the unstressed version, “blicket” and “toy” could reasonably refer to the same item. However, in the emphasized version, the additional focus through intonation suggests that “toy” is distinct from “blicket.” Without emphasis, only 24 percent of the children perceived the words as mutually exclusive, but with emphasis on “toy,” 89 percent believed “blicket” and “toy” referred to different things.
The second and third experiments demonstrated that focus is crucial not only for commonly known terms like “toy” but also while interpreting entirely new words like “wug” or “dax.” When a novel word was presented without focus, children thought it referred to the previous object 71 percent of the time. Conversely, when the new term was emphasized, they inferred it referred to a new object 87 percent of the time.
“Even if they have no familiarity with the new word, its focus conveys some information: it indicates a contrasting option, leading them to understand that the noun refers to something not previously named,” Aravind clarifies.
She adds: “Our primary assertion is that children do not inherently lean towards mutual exclusivity. The reason they make that inference is that focus indicates the new word differs from another word. When focus is absent, children do not make those exclusivity assumptions anymore.”
The team believes these experiments provide fresh insights into this topic.
“Previous theories on mutual exclusivity introduced new challenges,” Feiman notes. “If children assume words are mutually exclusive, how can they learn words that overlap? After all, an animal can be referred to as either a rabbit or a bunny, and children must learn both terms eventually. Our findings clarify why this isn’t problematic. Children do not default to mutual exclusivity for a new word unless informed otherwise by adults — all that adults need to do if a new word isn’t mutually exclusive is use it without emphasis, which they will naturally do if they consider it as compatible.”
Learning Language from Language
The researchers emphasize that this study resulted from interdisciplinary collaboration combining psychology and linguistics — using the concept of focus in linguistics to address a topic relevant to both areas.
“We hope this paper illustrates that simple theories have value in psychology,” Brody expresses. “It’s a small theory, not an extensive model of the mind, yet it radically changes our understanding of certain phenomena we thought we grasped.”
If this new hypothesis is accurate, the researchers could have formulated a more comprehensive explanation for how children effectively learn new vocabulary.
“A significant idea in language development is that children utilize their existing language knowledge to acquire further vocabulary,” Aravind states. “We are building on that notion, suggesting that even in the most straightforward cases, aspects of language they already understand, like focus, assist them in grasping the meanings of unfamiliar words.”
The researchers acknowledge that further studies could enhance our comprehension of this topic. Future research could revisit earlier studies on mutual exclusivity, record and analyze natural interactions between parents and children to assess how focus is utilized, and explore this issue in different languages, particularly those that express focus through alternative methods like word order.
This research received partial support from a Jacobs Foundation Fellowship awarded to Feiman.
