From mendel, this SciAm article about how children perceive is worth reading through, even if it gets a bit dry. My favourite quote:
By 18 months, babies have come to appreciate that a picture merely represents a real thing. Instead of manipulating the paper, they point to pictures and name objects or ask someone else for the name. Melissa A. Preissler of Yale University and Susan Carey of Harvard University recently provided a good example of this development. The two researchers used a simple line drawing of a whisk to teach 18- and 24-month-olds the word for this object that they had not seen before. Most of the children assumed the word referred to the object itself, not just to the picture of it. In other words, they interpreted the picture symbolically–as standing for, not just being similar to, its referent.
In other words, children are call-by-value, adults are call-by-reference. No wonder I preferred BASIC to C when I was 10…
Edit One last addition: Jonathan Coulton‘s Mandelbrot Set rules. Listen and buy his music! And ignore his misspelled name on Metafilter.
On the contrary, your favourite quote implies that children are call-by-reference. If they were call-by-value, the action performed on the data (i.e. associating it with the word “whisk”) would affect only the “local variable” (i.e. the drawing) and not the external referent, the real thing.