Part of what makes language so damn convenient is that it allows us to share information about things that aren’t around us.

Sure, many species of birds and primates can and do communicate the presence of predators to conspecifics (a fancy term for “members of the same species”). And bees famously waggle dance, communicating the direction and distance of remote food sources to their drone friends. But sans a full-fledged language, these animals would be hard-pressed to express more nuanced ideas—that the predators themselves are being chased by larger predators, or that the food source is inside the bed of a truck on its way to Tuscaloosa—even if they could think them. In other words, if Lassie gets too tired to lead rescuers to Timmy, it’s gonna be a long night in the well.

Human language has no such limitations, and we’ve built impressive civilizations that depend upon the transmission of knowledge about the distant and abstract.

Fortunately, we appear to acquire the ability to use language to attach new information to absent objects or people—that is, to “update” our mental representation of said object or person—before our second birthday.

In a 2007 study, psychologist Patricia Ganea, now of University of Toronto, and her colleagues Kristin Shutts, Elizabeth Spelke, and Judy DeLoache invited 19- and 22-month-old children into the lab. A researcher presented a toddler with three stuffed animals, two of which were identical (two frogs) and one which was not (a pig). Two of the animals went unnamed, but one of the frogs, the researcher explained, was called “Lucy.” Then the researcher and child played some simple games designed to familiarize the child with all of the stuffed animals. Once the toys were sufficiently old hat, and Lucy could be readily identified, the researcher led the child into a second room for story time.

At around this point in the study, a second researcher sauntered by, carrying a bucket of water. She loudly declared that she would be washing a table in the original playroom. Then, two minutes later she reappeared, claiming to have spilled: “Oh no! Lucy is wet now! She’s covered with water!” The child was led back into the room and shown all three stuffed animals. Two of them—the pig and one of the frogs—were wet. The child was asked to identify Lucy.

Unsurprisingly, hardly any of the children (regardless of age) pointed to the pig. They had learned that Lucy was a frog, and wouldn’t be fooled into thinking otherwise. And about 80 percent of the 22-month-olds selected the wet frog, suggesting that they had updated their representation of Lucy to reflect the new information. The 19-month-olds, however, were about equally likely to select the wet frog as the dry frog.

Note that it was not the case that the younger group simply didn’t understand the researcher when she claimed to have spilled the water on Lucy. In a follow-up study, the toddlers were led back into the playroom before the researcher’s confession (which was thus made in Lucy’s presence), and the 19-month-olds did just fine. Somewhere between the ages of 19 and 22 months, it would seem (perhaps slightly earlier in the comfort of our own homes, surrounded by our own playthings), most of us figured out how to learn about the world in its absence.