Human language enables us to learn new words for things we haven't directly experienced, often drawing on contextual clues during conversations to infer meaning seamlessly. But how early does this ability emerge, and what mechanisms allow for the creation of mental representations of unseen objects or events?

A groundbreaking study conducted by developmental scientists from Northwestern and Harvard Universities has revealed that infants as young as 15 months can recognize objects they have only learned about through language, even when those objects remain hidden.

For example, imagine an infant playing with blocks while overhearing a discussion about kumquats amidst familiar fruits like apples and bananas. Can the infant form a basic understanding—an initial "gist"—of what a kumquat might be? And can this understanding help them identify a kumquat when they later encounter it? These were the questions the researchers sought to explore.

Traditionally, many believe word learning requires physically mapping a word to an object in view (e.g., "Look at the kumquat!"). However, lead researcher Prof. Sandra Waxman emphasized that in daily life, infants, like adults, often encounter words referring to absent objects. She questioned whether infants could leverage the conversational context to infer word meanings.

In the study, 134 infants were divided into two age groups: 12 months and 15 months. They were guided through a three-step process. First, infants were shown familiar objects paired with corresponding words (e.g., "apple"). Next, they heard a novel word linked to a hidden object (e.g., "kumquat"). Finally, when presented with two novel objects—a kumquat and a whisk—they were asked to identify the kumquat. The findings? Fifteen-month-olds successfully identified the kumquat by looking longer at it, while 12-month-olds did not yet exhibit this ability.

These results highlight that 15-month-olds can use linguistic clues to form a mental representation of a new word's meaning. Even if the object isn't visible, they build a context-based "gist" that helps them make sense of its meaning later.

Prof. Waxman noted that 12-month-olds might lack sufficient understanding of familiar words in a given context to construct such a representation. Nonetheless, this research offers profound insights into the origins of humans' capacity to learn about absent objects through language. It underscores how infants, even before speaking fluently, harness linguistic input to develop meaningful representations of their world.

This study also sheds light on the immense power of language in shaping infant cognition. Whether through conversations or stories, infants frequently hear new words without immediate physical associations. By 15 months, they can effectively use these contexts to piece together meanings, setting a foundation for lifelong language learning.