That's the question an Australian-first research project at the ANU's Research School of Psychology's Child Cognition Unit is attempting to answer.
Unit director Dr Emma Axelsson said their team was trying to determine how children figure out and remember new words.
"If they hear a new word and they see a new object in the context of familiar objects, how do they then guess what it is?" Dr Axelsson said.
Using an eye tracker and pictures flashing on a computer display, toddlers aged 30 months are asked to point to the object they think corresponds with a new word they hear.
"They tend to rule out the familiar objects and objects they already have a name for so when they hear a new word, they tend to then select a new object, an object they've never seen before," Dr Axelsson said.
Half of the children in the sample group will then take a nap while the rest remain awake.
Four hours later, the researchers will measure their recall to see how many of their newly acquired words stuck.
"It's relatively new knowledge that sleep enhances memory so the question is napping useful for children's language development, that's probably one of the main questions we're looking at," Dr Axelsson said.
"They're constantly being bombarded with new things, new objects, new names and encountering new experiences all of the time. Regular napping might be helping them to remember what they're learning."
Raelene Arthur signed her daughter Mikaela up to the research project.
She said she's often surprised by the words that bubble out of the two-and-a-half-year-old's mouth.
"She'll come out with the strangest things. When she was about 18 months to two years, she would come out with things that I didn't even realise she knew or that I'd never said to her. That was weird," she said.
"When I saw this study I wanted to know where she was learning it, how she was picking it up."
Fittingly, Mikaela's word of the moment is "remember".
You can become involved in the Child Cognition Unit's toddler learning research by emailing email@example.com