at 20 months of age, when presented with three familiar objects (e.g., a ball, a bottle and a cup) and one unfamiliar object (e.g., an egg piercer), children are able to conclude that in the request “can i have the zib,” zib must refer to the unfamiliar object, i.e., the egg piercer, even if they have never heard that pseudoword before. children as young as 15 months can complete this task successfully if the experiment is conducted with fewer objects. this task shows that children aged 15 to 20 months can assign meaning to a new word after only a single exposure. fast mapping is a necessary ability for children to acquire the number of words they have to learn during the first few years of life: children acquire an average of nine words per day between 18 months and 6 years of age.