Summary: Infants as young as 15 months can use linguistic context to infer the meaning of words for objects they have never seen. In laboratory tests, 15-month-olds who heard a novel word embedded in a familiar conversation about fruits later identified the correct unseen object when it appeared, showing they had formed a mental “gist” of that word’s meaning from context alone.
This capacity to build an abstract representation without direct perceptual cues marks an important early milestone in language and cognitive development. The results show that babies are active learners: they extract meaning from the conversations around them and use those clues to guide future learning about unfamiliar objects and words.
Key Facts:
- Early word inference: By 15 months, infants can infer the meanings of previously unseen words from conversational context.
- Mental representation: Infants form a concise “gist” of a new word’s meaning even when the referent is not visible.
- Developmental insight: These findings illuminate how language exposure supports abstract learning during infancy.
Source: Northwestern University
Human language allows us to think about people, objects, and events that are not present. We regularly learn new words from context—picking up meaning from the surrounding conversation rather than immediate visual cues. But when does this ability first appear in development, and how early can infants form mental representations of things they have never seen?
A recent study conducted by developmental researchers at Northwestern University and Harvard University provides the first clear evidence that 15-month-old infants can form and later use a mental representation of an object’s word meaning even when the object was hidden during learning.
Picture a baby playing with blocks while overhearing a conversation about familiar fruits—apples, bananas—during which someone casually mentions a new word, such as “kumquat.” Could the infant infer that “kumquat” refers to another edible fruit and later use that inference when first encountering an unfamiliar fruit? The researchers designed an experiment to test exactly this kind of context-driven learning.
Many people assume that successful word learning depends on a child hearing a word while seeing the object it labels. Yet in everyday life infants often hear words when their referents are not present. The team, led by Sandra Waxman, asked whether infants can rely on conversational context to begin forming word meanings.
Waxman is the Louis W. Menk Professor of Psychology, director of the Infant and Child Development Center, and an Institute for Policy Research fellow at Northwestern. The study’s co-author is Elena Luchkina, formerly a postdoctoral fellow at Northwestern and now a research scientist at Harvard.
The study tested 134 infants in total: 67 at 12 months and 67 at 15 months. The experiment had three stages. First, infants were shown familiar words paired with images (for example, apple, banana, grapes) to prime a semantic category such as “fruits.” Next, while an unfamiliar object was hidden from view, infants heard a novel noun used in the same conversational context as the familiar words. Finally, two novel objects appeared side-by-side—one that matched the primed category (e.g., a novel fruit) and one from a different category (e.g., an unrelated artifact)—and the test question asked the infant to identify the novel noun (for example, “Where is the kumquat?”).
Fifteen-month-olds reliably looked longer at the novel fruit than at the novel artifact, indicating they favored the candidate that matched the primed semantic neighborhood. Twelve-month-olds did not show this preference. In other words, 15-month-olds had used contextual cues during the hidden-word phase to build a meaningful gist for the new word and then applied that gist when choosing the referent later on.
“The study shows that even babies who are just beginning to speak learn from the language they overhear, even when the objects being discussed are not present,” said Waxman. “Infants form a mental representation—a succinct gist—of a new word’s meaning from context, and that representation can guide their choices when the referent finally appears.”
Waxman and colleagues suggest that 12-month-olds may not yet have a sufficiently large or well-established vocabulary of familiar words to benefit from this kind of contextual priming. Their representations of new nouns may be too sparse to guide referent selection when the object later becomes visible.
Gleaning the meaning of “kumquat”
By introducing novel words without any visible referent, the researchers provided a rigorous test of how much infants can learn from language alone. The findings reveal when and how the human capacity to create mental representations of unseen things emerges: between 12 and 15 months of age.
This work underscores the everyday power of language in infants’ lives. In natural settings—during conversations and book reading—babies hear many words they cannot immediately map onto a visible object. The study demonstrates that by 15 months infants spontaneously use linguistic context to form initial meanings that support later learning.
“When adults hear a new word in conversation with no referent present, we still use the context to home in on its meaning,” Waxman said. “This study shows that very young infants do the same.”
About this language and learning research news
Author: Stephanie Kulke
Source: Northwestern University
Contact: Stephanie Kulke – Northwestern University
Image: The image is credited to Neuroscience News
Original Research: Open access. “By 15 months, infants begin to learn new words for objects, even those they’ve never seen” by Sandra Waxman et al., PLOS One
Abstract
By 15 months, infants begin to learn new words for objects, even those they’ve never seen
Human language lets us form mental images of objects, events, and ideas that are not directly perceptible, expanding what we can learn beyond the here and now. When does this capacity emerge in infancy? To investigate, researchers tested 12- and 15-month-old infants to see whether they could form a representation of a novel noun’s meaning when no visible referent was present, and then use that representation to identify a candidate referent when it later appeared.
During training, infants were exposed to words and images from a particular semantic category (for example, fruits) and then introduced to a novel noun used to name a hidden object. At test, the noun was played again while two unfamiliar objects were visible: one matching the primed category and one unrelated. If infants had formed a representation of the novel noun’s meaning from context alone, they should prefer the object from the primed semantic neighborhood.
Fifteen-month-olds succeeded: they preferred the object from the primed category. Twelve-month-olds did not, even after additional vocabulary training designed to strengthen priming. These results suggest that between 12 and 15 months infants develop the capacity to establish a representation of a novel noun’s meaning in the absence of any visible referent and to use that representation to select a likely referent when one appears.