The project has a cross-cultural focus and investigates categorisation in a wide array of domains (see subprojects), with a view to answering core theoretical questions. For example:

• Where do linguistic categories (both lexical and grammatical) come from – that is, what factors induce just these categories and not others? Are they composed from features at other levels, perceptual and conceptual (consider, e.g., colour words), or do they have a life of their own (consider, e.g., aspectual distinctions)?
• How variable are linguistic categories across languages? What kinds of semantic parameters are universal, or at least recurrent, and which not? Are categories of relations between entities more cross-linguistically variable than simple categories of entities, for example? Are the conceptual categories in grammar (e.g. tense, aspect, number) more universal than lexical categories, or is it the other way around?
• Given cross-linguistic diversity, how do children learn linguistic categories? Is there a common basis from which to start, "natural categories" as it were? Which kinds of linguistic categories are easiest to learn – grammatical or lexical, nominal or verbal ones?
• Why are certain perceptual modalities favoured in linguistic categories, e.g. visual over haptic or olfactory? Why are there conceptual categories that cannot be verbalized (e.g. familiar faces, smells)? To what extent do linguistic categories fuse percepts across different modalities (as perhaps in velvety 'reflective and smooth')? To what extent do categories from some sensory modalities provide linguistic concepts for other modalities (as in visuospatial metaphors for time, haptic and visuospatial metaphors for sound e.g. high sharp noise)?
• What role do linguistic categories play in non-linguistic cognition – e.g. in memory, perception and reasoning? What mechanisms are involved in propagating linguistic categories into other conceptual and perceptual levels (e.g., 'priming', 'retrieval', 'internal monitor as logic checker', 'chunking')?