The linguistic studies referred to in 1.4.2 to 1.4.6 indicate that linguistic
categories influence at least three different levels of thought:
1. Perception, as when the "name strategy" is used in forming judgements about the
relative distance between colours.
2. Classification, as when the shape/form categories of the Navaho verb system
prompt Navaho-speaking children to classify objects on the basis of shape/form, or
when the distinction between count nouns and mass nouns in English prompt English
speakers of all ages to distinguish sharply between objects and substances.
3. Abstract thinking, as in the case of mathematics and counterfactual reasoning.