A unique study has thrown fascinating new light on how young children begin to understand the meaning of words.
The researchers, from The University of Manchester publish their findings in the journal Child Development.
Children start to say words around their first birthday, and for a while only say one word at a time, though they rapidly build their vocabulary during their second year.
But the researchers found they do not do this by adding a complete form of new words to their own personal dictionary.
Instead, they put a new word in their dictionary which has some, but not all of the meaning, slowly finetuning it as they hear more language.
To show how children do this, the researchers set up a study in Manchester Museum, working with a group of three to eight-year olds.
An experimenter built either 4 blocks stacked up, or 4 blocks lined up flat on a table, and then the children were asked to respond to different size words by building a bigger, smaller or taller version.
The researchers compared how their structure differed from the experimenter's in each dimension , using mathematical modelling to describe what types of changes children made, and how patterns varied with age.
Three and four-year-olds tended to treat bigger, smaller, and taller with the same meaning: they built things that were bigger in all directions.
"It seems that when children first learn words, they pick up a general idea of what they mean- in this case, that the words mean a size change", said co- author Dr Alissa Ferry, a lecturer at The University of Manchester.
"This seems to be how we end up with children calling a cow a dog, or all round fruit apples, even though they've never heard an adult do that. But with more experience they fine tune their word meanings.
"We do think all children go through this process of fine-tuning word meanings, but which words are fine-tuned and when depends on what they hear around them."
"Size words", explained Co Author Dr Katherine Twomey, also from the University of Manchester, "are trickier to learn because they describe relations between all different kinds of objects, which makes it harder to find what is common.
"That makes it easier for us to see how the meaning changes with age development."
By around age 5, the children generally worked out that smaller meant they should use fewer blocks.
But it was not until about age seven they reliably worked out that taller really means bigger but specifically in the 'up' direction.
Most of the 3-year-olds built bigger things when the researchers asked for smaller ones, though some of them seemed to work it out faster than others.
It was not until about age 7 when most of the children knew that taller meant specifically 'up'.
However some 3- and 4-year-olds already seemed to know that taller meant 'up', probably because they had exposure to those words more frequently in conversations with their caregivers.
Dr Ferry added: "Learning a language is a uniquely human experience; children just pick it up from being exposed to it.
"Yet, we don't quite know how that happens, which is why we carried out this study."
Also on the research team were four sixth form Nuffield Research Placement summer internship students who helped design and collect the data.
The paper Bigger Versus Smaller: Children's Understanding of Size Comparison Words Becomes More Precise With Age is published here
